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New propositions about coffee wet processing: Chemical and sensory perspectives
Journal Pre-proofs New propositions about coffee wet processing: Chemical and sensory perspectives Lucas Louzada Pereira, Rogério Carvalho Guarçoni, Patrícia Fontes Pinheiro, Vanessa Moreira Osório, Carlos Alexandre Pinheiro, Tais Rizzo Moreira, Carla Schwengber ten Caten PII: DOI: Reference:
S0308-8146(19)32082-5 https://doi.org/10.1016/j.foodchem.2019.125943 FOCH 125943
To appear in:
Food Chemistry
Received Date: Revised Date: Accepted Date:
15 April 2019 21 October 2019 20 November 2019
Please cite this article as: Pereira, L.L., Guarçoni, R.C., Pinheiro, P.F., Osório, V.M., Pinheiro, C.A., Moreira, T.R., ten Caten, C.S., New propositions about coffee wet processing: Chemical and sensory perspectives, Food Chemistry (2019), doi: https://doi.org/10.1016/j.foodchem.2019.125943
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New propositions about coffee wet processing: Chemical and sensory perspectives Lucas Louzada Pereiraa*, Rogério Carvalho Guarçonib, Patrícia Fontes Pinheiroc, Vanessa Moreira Osórioc, Carlos Alexandre Pinheiroc, Tais Rizzo Moreirad, Carla Schwengber ten Catene aFederal
Institute of Espírito Santo. Department of Food Science. Avenida Elizabeth Minete Perim,
S/N. Bairro São Rafael, Venda Nova do Imigrante, Espírito Santo, Brazil, CEP: 29375-000. E-mail: [email protected], ORCID: 0000-0002-4436-8953. bCapixaba
Institute of Technical Assistance, Research and Extension – INCAPER. Department of
Statistics. Rua Afonso Sarlo, 160 - Bento Ferreira, CEP:29052-010. Vitória, Espírito Santo, Brazil. Email: [email protected]. cFederal
University of Espirito Santo. Department of Chemistry and Physic. Center for Exact, Natural
and Health Sciences. Alto Universitário, sn, Guararema, Alegre, Espírito Santo, Brazil, 29550-000. Email: [email protected], [email protected], [email protected]. dFederal
University of Espirito Santo. Center of Agrarian Sciences and Engineering. Av. Gov.
Lindemberg, 316 - Centro, Jerônimo Monteiro, Espírito Santo, Brazil, 29550-000. E-mail: [email protected], ORCID: 0000-0001-5536-6286. eFederal
University of Rio Grande do Sul - UFRGS *. Graduate Program in Production Engineering.
Av. Osvaldo Aranha, n 99/5º andar, Bom Fim, CEP: 90.035-190 – Porto Alegre, Rio Grande do Sul, Brazil. E-mail: [email protected], [email protected]. *Corresponding author: Lucas Louzada Pereira. E-mail: [email protected]
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Abstract The interactions between edaphoclimatic factors, forms of processing, drying, storage and roasting, directly affect the sensorial results. This study applied four forms of wet-processing in six different altitude strata, aiming to potentiate the final quality of the drink. The final quality of the coffees was measured using the sensory technique and HS-SPME-GC/MS analyses. Results indicate that the use of starter culture in the fermentation phase constitutes a relevant alternative for lower-altitude zones, and that spontaneous fermentations have a higher potential of sensorial results at above 900 meters. In the sequence, the volatile compounds were affected according to the type of processing and the altitude. The compounds in general that contributed the most to the formation of the math models were: 2furylmethanol, octadecanal, 2-acetyl-3-methylpyrazine, 2,3-Dihydro-3,5-dihydroxy-6-methyl-4Hpyran-4-one (DDMP) and caffeine. The positive effects of the fermentation corroborate with new sensory routes, modification of the flavor and volatile compounds, consequently, generating new fermentation strategies.
Keywords:
Arabica
coffee,
Fermentation,
HS-SPME-GC/MS,
Sensory
Analysis.
2
1. Introduction The coffee production chain is complex and has great importance to producer and consumer countries, making it a strategic product for the world economy. Nine million tons of coffee are consumed worldwide each year, according to data from the United States Department of Agriculture (USDA, 2019). Several factors interact and influence production, harvesting, processing, drying, storage and roasting, until they are reflected in the evaluation of the quality of the coffee, both for agronomic and chemical aspects and for microbiology. The coffee quality is established by the level of the property and the processing techniques adopted. The most important operations and that will determine the quality of the final drink happen at the coffee farms (Velmourougane, Bhat, Gopinandhan, & Panneerselvam, 2011). But the roasting is primarily intended to cause chemical changes in the coffee bean resulting in the formation of desirable flavor compounds (Anisa, Solomon, & Solomon, 2017). From a processing perspective, Arabica coffee can be conducted in different ways, according to the post-harvest processing characteristic of each microregion. Usually, there are two ways of processing coffee after harvest: keeping the fruit intact, commonly called natural coffee (dry); or wet processing, which can be understood and unfolded in three ways: removing only the bark and part of the mucilage1, called peeled cherry (PC); removing the bark and mucilage mechanically (without mucilage); or removing the bark mechanically and mucilage by fermentation (pulped) (Reinato, Borem, Cirillo, & Oliveira, 2012). These processes are usually complex; each coffee grower has its variations in methodologies in the post-harvest. Often, there is no agreement and exact standardization for wet processing. The wet-processing technique is widely adopted by several Central American countries, resulting in pulped, peeled or demucilated coffees, with presence of the fermentative phase. Many producers use
The mucilage (mesocarp) is located between the bark and the coffee bean, representing on average 5% of the dry weight of the fruit. According to Borém, Marques, & Alves (2008), the amount of sugars in the mucilage of the mature fruit increases the risk of fermentations, which can compromise the quality of the coffee. 1
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this technique to avoid harmful or phenolic2 fermentation during fruit drying (Dias, Borém, Pereira, & Guerreiro, 2012). In addition to the factors associated with processing, it is known that coffees from higher regions usually receive more expressive notes on flavor, aroma, sweetness and body than coffees from warmer regions, as can be seen the literature (De Bruyn et al., 2016). This factor has been associated to the fact that high temperatures prevent the translocation of some chemical compounds to the fruits (Bosselmann et al., 2009), thus being able to constitute a natural terroir for these micro-regions. The coffees have intrinsic quality, derived from the specific characteristics of the region where they are grown (Ferreira, Queiroz, Silvac, Tomaz, & Corrêa, 2016). This systematic approach researches the coffee ecosystem, contributing to a deeper understanding of coffee processing, and could constitute a state-of-the-art framework for further analyses and subsequent control of this complex biotechnological process (De Bruyn et al., 2016). The effect of microorganisms present in the coffee plant and the post-harvest, such as Debaryomyces, Pichia, Candida, Saccharomyces Kluyverie S. Ceverisiae (G. V. de M. Pereira et al., 2014; Schwan & Fleet, 2014); or filamentous fungi, such as Aspergillus, Penicillium, Fusarium and Trichoderma; as well as bacteria, Lactobacillus, Bacillus, Arthrobacter, Acinetobacter, Klebsiella (Evangelista, Miguel et al., 2014; Evangelista, Silva et al., 2014; Quintero & Molina, 2015; Velmourougane, 2013), can affect the final coffee quality. However, the presence of different microorganisms during coffee fermentation has been get more attention in the literature over the last years (Ribeiro et al., 2017). So the ability of these microorganisms to affect coffee has become an opportunity to optimize the coffee production process (Lee, Cheong, Curran, Yu, & Liu, 2015, 2016). Although altitude is empirically known to have beneficial effects on coffee quality, only a few scientific studies have actually documented these effects (Joët et al., 2010). New perspectives emerged with the aim of potentiating the coffee quality curve through induced fermentation, reinforcing the discussion about fermentation, considering that desirable attributes can be optimized during wet processing (Lee et al., 2015). Phenolic fermentation has been pointed out in scientific studies, through sensory analysis of coffee, as a fermentation phase in which the coffee presents the drink as Riada or Rio, being this one with slight taste of iodoform or phenol by virtue of the repugnant flavor to the palate. 2
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Thus, we observe two hypotheses in this study, the first (i) is that different forms of processing modify the sensorial and chemical structure of the coffee, and the second (ii) is that the altitude acts as a factor that interacts with the process, indicating that certain processes respond better depending on the natural condition of production (terroir).
2. Materials and Methods 2.1 Collection of fruits carrying out the experiments Fruit collection was carried out from June to October 2016 in six properties in areas that have a history of production of specialty coffees according to the Specialty Coffee Association's (SCA) technical quality parameter. According to the SCA, coffee which scores 80 points or above on a 100point scale is graded as a specialty coffee (Figure 1). The fruits presenting 85% of maturation were selected for the via-wet process, and the buoyant and green fruits were discarded, not being considered in the sensory and chemical analysis. The coffee fruits were harvested manually, without any contact with the soil. After harvesting, the fruits were stored in hermetic Grainpro bags and were processed on the same day. 2.2 Experimental design After harvesting, the coffees were taken to the processing unit to be washed in 1000-liter plastic boxes to separate the floating fruits. After washing, the fruits were peeled with the DPMM-04 equipment (coffee peeler), from Pinhalense. The fresh pulp and coffee husk were separated for fermentation and must formulation. The fresh water used in the processing of the coffees in both experiments is in accordance with CONAMA guideline n. 357/2005, which deals with the classification of water bodies (Prezotti, Gomes, Dadalto, & Oliveira, 2007). The raw materials used in the formulation of the musts were composed of coffee pulp, bark from peeling, water and yeast (Saccharomyces cerevisiae). Fifteen kilograms of coffee were harvested per experimental plot in all experiments, and after harvest the fruits were processed according to established procedures. Six points were selected by the authors to develop this study in different places of the state of Espírito Santo.
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Figure 1 shows that the samples came from areas with altitudes of 774 m; 788 m; 893 m; 907 m; 1004 m and 1033 m. The experiments were conducted following a randomized block design with five replicates. The process was composed of fermentation in module washed (fermentation with water), yeast fermentation (fermentation with yeast culture), fully washed fermentation (dry, using peeled and demucilated cherries by means of fermentation), and semi-dry fermentation (peeled and dried with remaining mucilage). All the fermentation processes were developed in the Coffee Analysis and Research Laboratory (LAPC), in controlled process. Fig. 1 (Link text) - Map of the location of the experimental points. Of the four proposed processes, a must was prepared from the patent process BR10201600405313, with yeast culture (Saccharomyces cerevisiae) and coffee husk. The four processes had the following steps: Treatment 1: fermentation of must with water (Washed), 10 kg of peeled cherry coffee (pulp), 5 kg of bark (the husk was collected from the coffee pulp and added to the must) and 5 liters of water; Treatment 2: fermentation of must with yeast starter culture (Saccharomyces cerevisiae – Yeast fermentation) in 1% (p/v4) of must, 10 kg of pulped coffee (pulp) and 5 kg of bark (the husk was collected from the coffee pulp and added to the must), 5 liters of water; Treatment 3: dry fermentation must (Fully washed without yeast), 10 kg of peeled cherry coffee (pulp), and 5 kg of bark (the husk was collected from the coffee pulp and added to the must), without additional water; Treatment 4: 10 kg of peeled cherry coffee (pulp), coffee husked without removal of the mucilage (semidry), without any addition of micro-organisms. For the experiments, musts 1 and 2 received addition of water to the process at the temperature of 38ºC (G. V. de M. Pereira et al., 2015) and remained immersed in fermentation tanks in the processing laboratory of the Federal Institute of Espírito Santo (IFES), Venda Nova do Imigrante Campus, Espírito Santo, Brazil, for 36 hours. Must 3 received only bark originating from
3 4
Patent process deposited with the National Institute of Industrial Property (INPI). Part by volume (quantity of micro-organism as a function of must).
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the wet processing and was in fermentation process for 36 hours. Must 4 was taken to drying in a suspended and covered yard immediately after the debarking process. After the fermentation period, musts 1, 2 and 3 were washed and dried in a suspended and covered yard (African Bad – Up-high system to dry). The coffees were sun dried for a period of 15 to 18 days in a covered suspended system (plastic cover), with an average temperature of 19.54 °C, with a maximum of 45.72 °C (day) and minimum of 9.07 °C (at night). Temperature was monitored by the Arduino Uno R3 system - Bluetooth Module Hc-06 Rs232 - Humidity and Temperature Sensor Dht22 Am2302 - SD card module. 2.3 Sensory analysis via the Specialty Coffee Association protocol The SCA sensory analysis protocol was applied to this study with 6 Q-Graders5. The number of Q-Graders in a sensory panel was initially proposed by L. L. Pereira, Cardoso et al., (2017). The quality of a coffee, once evaluated through the SCA (2013) protocol, is expressed by a centesimal numeric scale. The tasting form provides the possibility of evaluating eleven (11) important attributes to the coffee: Fragrance/Aroma, Uniformity, Clean cup, Sweetness, Flavor, Acidity, Body, Aftertaste, Balance, Overall and Global Score Evaluation. 2.4 Preparation of samples for tasting The samples were prepared in the coffee sensory analysis laboratory of the Federal Institute of Espírito Santo, Venda Nova do Imigrante campus. The roasting process was conducted using the Laboratto TGP-2 roaster with the Agtron-SCA disk set, and the roasting point of these samples was between the colors determined by the # 65 and # 55 disks for special coffees (SCA, 2008). The roasting process was executed 24 hours in advance and the grinding respected the time of 8 hours of rest after roast. All the samples were toasted between 9 and 10 minutes and, after roasting and cooling, the samples remained sealed, according to the sensory analysis methodology established by the SCA. The coffee samples were ground with a Bunn G3 electric grinder, with medium/coarse particle size. Each batch of coffee was tasted with 5 cups, and the optimal concentration of 8.25 grams
5 Q-Grader: Q-Graders are qualified, controlled, and professionally trained coffee tasters at the Coffee Quality Institute (CQI).
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of ground coffee in 150 mL of water was adopted, according to the midpoint of the equilibrium graph optimum for obtaining the Golden Cup (SCA, 2008). The infusion point of water was when the water reached 92-95 ºC. The Q-Graders began the evaluations when the temperature of the cups reached 55 ºC, respecting the time of 4 minutes for tasting after the infusion. 2.5 Analysis of volatile compounds Roasted and ground coffee samples were extracted by HS-SPME-GC/MS (solid phase microextraction using the headspace mode, combined with gas chromatography coupled to mass spectrometry). To do this, 3g of these milled and roasted coffees were weighed into a suitable headspace vial (20 mL glass vial), with a magnetic screw cap and silicone septum, which was subjected to heating at 70 ºC for 30 minutes. The volatiles were collected by HS-SPME using the DVB/CAR/PDMS fiber (Divinylbenzene/Carboxene/Poldimethylsiloxane, 50 μm film thickness) and injected into the gas chromatograph coupled to the QP-PLUS-2010 mass spectrometer Shimadzu. The molten silica capillary column used was Rtx-5MS (30 m in length and 0.25 mm in internal diameter). Helium was used as drag gas, with flux of 1.67 mL/min. The temperature of the injector was 250 °C and the detector 300 °C. The initial column temperature was 40 °C, being programmed to have increments of 3 °C every minute until it reached the maximum temperature of 125 °C where it remained for one minute, then the temperature was increased to 10 °C per minute until reaching the temperature of 245 ºC, which was held for 3 minutes. To determine the chemical constituents, the mass spectra obtained were compared to those of the apparatus library (Wiley7, NIST08), with data from other studies and with the retention indices (Adams, 2007). In order to calculate the retention indices (RI), a mixture of linear alkanes (C8 to C23) was injected into the chromatograph under the same conditions used in the analysis of the coffee volatiles (Franca, Oliveira, Oliveira, Agresti, & Augusti, 2009). 2.6 Statistical analysis For the statistical analysis, a joint analysis of variance of experiments was performed on the sensory results. The means were compared by Tukey’s test considering the level of significance of 5 %, and the regression models were tested by the F-test and the t-test parameters.
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Dendrograms were constructed using the mean Euclidean distance to measure the distances between the 24 points (6 altitudes x 4 processing) of sensory analysis according to Table 1 and gas chromatography data, and the points were grouped by the Hierarchical Full Linking method. The idea is to maximize the homogeneity of objects within groups, while maximizing the heterogeneity between groups. The regression models of the chromatography data were tested by the F-test and the parameters by the t-test. Statistical analysis was performed using the software SPSS version 22.
3. Results and Discussions 3.1 Sensory analysis The results of the global sensory score of the coffees processed in this study are presented in Table 1, where the results obtained by means of the joint analysis of experiments for the sensory characteristic of the coffees studied in the regions between 774 and 1,033 meters of altitude were described, followed by regression models. Table 1 (Link text) - Averages of the global characteristic score evaluated in four processes and at six altitudes, followed by regression models.
All processed coffees obtained special scores when considering the general average of the processing. It is observed, however, that the action of yeast (Saccharomyces cerevisiae) improved coffee quality. Processes 2 and 4 did not present any differences (p<0.05) between themselves at 774 meters of altitude (Table 1). Method 4 is different from all others; the processes for methods 2 and 3 are the same; however, method 3 does not differ from methods 1 and 2; finally, method 1 presents the worst sensory result in a global score, but not different from method 3 (Table 1). The improvement of coffee quality with yeast inoculation in the lower part, as mentioned above, may be associated with microbiota. This result may be associated to the fact that high temperatures prevent the translocation of chemical compounds to the fruits, opening a field for discussion about the microbiota of coffees belonging to warmer areas to the detriment of higher
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zones. In this perspective, it is observed that the action of the crops starters was effective (Evangelista, Miguel et al., 2014; Lee et al., 2015). In the experiment conducted at 788 meters of altitude, processes 2, 3 and 4 did not differ from each other (p<0.05). Method 1 was the one that got the worst sensory results. It was possible to observe a trend in method 2 on the overall score, that is, the yeast culture provides a slight increase in quality in this experimental range. For the experiments conducted at 893 and 907 meters of altitude, processes 1, 2 and 4 did not present differences among themselves (p<0.05); method 3 differed from method 1, but not from the others. The Fully washed method (3) presented the worst sensory results for this altitude. The technique of Fully-washed processing is spreading rapidly based on empirical evidence and without much theoretical scientific support, that is, it is clear and evident that the changes that occur in the fermentation process must be better studied (Schwan & Fleet, 2014). In the experiment conducted at 1004 meters, processes 1 and 4 were not different (p<0.05). Method 2 is not different from method 3 and 4, but method 4 differed from method 3. The processes carried out in this area indicate expressive results on the quality of the coffees, with the highest sensory score among all the experiments: 87.67 for method 1, followed by method 4, with 87.09. The method employed for the yeast Saccharomyces cerevisiae suffered a considerable reduction in the sensory mark, evidencing that the inoculation of starter cultures provided a reduction of the sensory score of coffee in the 1250 meters of altitude range, when compared to the spontaneous fermentation method, in the cerrado region of Minas Gerais (G. V. de M. Pereira et al., 2015). At the altitude of 1033 meters, method 1 differed from all others. The highest sensory scores for this range were observed using the washed-water method, with 85.39 points of global score. This result reinforces the spontaneous fermentation condition. Under these results, it is suggested that spontaneous fermentation may be more favorable for areas above 893 meters, due to the natural microbiota of the coffees, which can be confirmed by the significant linear functional relation between global and altitude, for this method processing technology (Table 1).
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These results reinforce the cut off limit for the use of starter cultures or the more adequate selection of each microorganism, respecting the coffee microbiota, since, during coffee fermentation, the bacteria, yeasts and enzymes will act in the degradation of the mucilage, transforming pectic compounds and sugars into alcoholic and organic acids (Martinez, 2013; Somporn, Kamtuo, Theerakulpisut, & Siriamornpun, 2012). The effects of fermentation during wet processing on the coffee flavor profile are not fully explained and are often neglected, since the literature has argued that the main function of fermentation is the removal of mucilage (Lee et al., 2015). Concomitant to the sensory results according to the process employed, the regression models indicate that water-washed fermentation provided improved coffee quality due to altitude, followed by method 3 (Fully washed), which shows that the microbiota present in the fruits is able to take charge of the fermentative processes and that the fermentative action occurs to solubilize polysaccharides6 that are present in the coffee pulp. Consequently, during the fermentation, microorganisms will act in the degradation of the sugars present in the pulp, creating metabolic routes and different sensorial patterns. This factor corroborates that the wet process method significantly influences the microbial community structures and hence the composition of the final green coffee beans. This systematic approach to the coffee ecosystem contributes to a deeper understanding of coffee processing and subsequent control of this complex biotechnological process (De Bruyn et al., 2016). The hierarchical grouping analysis was performed for all sensory attributes by altitude zones. It suggests the existence of two homogeneous groups in the dendrogram: group A formed by points (altitude / method) from 1 to 8, 10 to 16 and 22 to 24; and group B formed by the other points (9 and 17 to 21) according to Fig. 2. Fig. 2 (Link text) – 24-point Dendrogram (6 altitudes and 4 processes). The separation and formation of the sensory groups through multivariate analysis evidenced that the washed method in three altitude zones agglutinates in Group B, indicating that the best global
Polysaccharides are carbohydrates that by hydrolysis originate a large number of monosaccharides and these are constituted by natural polymers. 6
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scores are in agreement. Point 9 (method 1 - washed - at the third altitude - 893 meters), followed by point 17 (method 1 - washed - at the fifth altitude - 1004 meters), ending with point 21 (method 1 washed - altitude - 1033 meters) have higher notes than all other points. Points 18, 19 and 20 belong to the fifth altitude and are grouped at experimental points with higher altitudes (Fig 2). All the coffees with the lowest global scores are in group A, which does not indicate a trend, as observed in group B for the best coffees. The results suggest that coffee processed only with water, through spontaneous fermentation, known as washed, favored the final quality. The same results were observed by Quintero & Molina (2015), and Rendón, Salva, & Bragagnolo (2014). The formation of group B, through spontaneous fermentation processes, indicates the occurrence and action of natural microorganisms, which can generate qualitative gains in these three areas. This interaction between the environment and global coffee quality has been briefly discussed by Joët et al. (2010), indicating the fact that most of the changes occurring in coffee and processing can be interpreted by physiological processes, as well as the effects of temperature during fruit formation, followed by hypoxic conditions during wet processing, a fact confirmed by Somporn et al. (2012). These compounds that are influenced by the environment (climate) need to be better evidenced. The results show that the method of spontaneous fermentation in the wet-process through the washed method can be more promising than the use of yeasts in zones of higher altitude, respecting the characteristic terroir of each region, and that yeasts, especially the S. cerevisiae, can be applied to areas less favored by natural climatic conditions and that such biotechnological applications can provide quality gains, as evidenced in the construction of sensory routes by Evangelista, Miguel et al. (2014) and Evangelista, Silva et al. (2014). 3.2 Multivariate analysis of volatile compounds In addition to the sensory analyses, the results of the volatile compounds are discussed in this section. In total, 98 compounds were found in all roasted coffees. Of the total volatiles found, 28 were identified. The multivariate analysis using dendrograms was used to understand the results regarding volatile compounds, ending with the regression models observed between processes and altitude for the compounds. 12
Fig. 3 shows the existence of two homogeneous groups: Group A, formed by points (altitude/processes) 1 to 4 and 9 to 12. In sequence, other group, B, formed by the other points. For group A, similarities were observed between all processing at altitudes 1 and 3. Fig. 3 (Link text) – 24-point Dendrogram (6 altitudes and 4 processes) on the volatile compounds observed. Analyzing the results shown in Fig. 3, based on the formation of the groups, it is possible to infer that the experiment located at 774 meters is grouped (1 to 4) with the experiment of the third band at 893 meters (9 to 12); Both have are similar due to their chemical compounds, and their processes. The compounds that contributed the most to the formation of the models were7: C5: 2furylmethanol, with 14.1 %; followed by the compounds C27: octadecanal, with 8.33 %; and C11: 2acetyl-3-methylpyrazine, with 7.61 %; C12: 2,3-Dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP); and C23: caffeine, each 7.61 %. The sweet-caramel-nut-flavored 2-furylmethanol compound was one of the compounds that most contributed to the formation of mathematical models. According to Casas et al. (2017), this is a compound found mainly in immature coffee seeds; however Ciaramelli, Palmioli, & Airoldi (2019) describe that 2-furylmethanol is present in coffee beans when trigonelina is decreased in the roasting process. Aldehyde compounds such as octadecanal are not commonly mentioned as a volatile compound present in coffee. Fatty acids are known as important components that can confer flavor and aroma, but few studies have described the relationship and effect of such compounds on coffee quality (Figueiredo et al., 2015). The logical explanation for the formation of this compound can be given by the hydrogenation of linoleic acid in fatty acids, releasing stearic acid, because the reduced stearic acid releases the octadecanal compound, and then the main reaction pathway occurs with octadecane decarboxylation in heptadecane (Li, Wang, Liu, Zhou, & Fu, 2017).
The volatile compounds are arranged from the letter C, followed by the code referring to the retention time of the sample in the chromatography analysis. 7
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The third compound with higher weight in the dendrogram is classified within the pyrazines group. 2-acetyl-3-methylpyrazine is a volatile compound characterized by a sweet potato aroma and strong presence of nuts and cereals. More than 80 pyrazines have been identified in roasted coffee. Some ketones may subsequently participate in reactions that lead to the formation of pyrazines or Strecker aldehydes. For 2-acetyl-3-methylpyrazine, no significant functional relationships were observed between the signal area of the compound and the altitude for all the process. Compounds such as 2,3-Dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, which belong to the terpene class, have already been described by Lee et al. (2016) as a compound formed by biosynthesis in S. cerevisiae fermentations, and DDMP is described as an antioxidant compound according to Yu, Zhao, Liu, Zeng, & Hu (2013). The metabolites generated by the fermentation may confer some differentiated characteristics to the coffee. The formation of 2,3-Dihydro-3,5-dihydroxy6-methyl-4H-pyran-4-one can be explained by the direct connection with processes of fermentation (Li et al., 2017). This compound has sweet, caramel and nut characteristics. The brown sugars have predominantly caramel flavors and, to a lesser extent, acidic characteristics due to the presence of components such as butanoic acid as well as 3-methylbutanoic acid together with 2,3-Dihydro-3,5dihydroxy-6-methyl-4H-pyran-4-one,
5-methyl-2-pyrazinylmethanol
and
2,5-dimethylpyrazine
(Asikin et al., 2016). Finally, the last volatile compound to contribute relative weight to the dendrogram construction is caffeine, or 1,3,7-trimethylxanthine. The volatilization of caffeine amounts to 3% of its total. The fatty matter and the ethereal oils decompose, to a great extent, within the cell walls. Caffeine is odorless and has a very characteristic bitter taste, contributing with a bitterness that is important to the taste and aroma of coffee. There is a possible correlation between the amount of stearic acid and the climatic conditions in which coffee is planted, which puts in discussion the action of climate in the formation of this acid (Rendón et al., 2014). The presence of this compound has not been readily detected in Arabica coffee. Significant functional relationships between the compost area and the altitude were observed for the dry or Fully-
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washed fermentation method discussed later for 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4one. Of the compounds, 2-furylmethanol, octadecanal, caffeine, 2,5-dimethyl-3-ethylpyrazine, 2acetyl-3-methylpyrazine, 4-ethenyl-3-methoxyphenol and methyl palmitate were the most representative compounds among all coffees (Fig. 4). Fig. 4 (Link text) - General mean of the distribution of volatile compounds of Arabica coffee in all processes and areas of study. The volatile compounds were also grouped due to the altitudes and processing in groups A and B (Fig. 5). Fig. 5 (Link text) - New groupings of volatile compounds due to the altitudes and methods observed in both groups A and B shown in Figure 3. Four homogeneous groups were found: group C, formed by point 1; group D, formed by points 2 to 4; group E, formed by point 5; and finally, group F, formed by points 6 to 8. It was observed that the method of spontaneous washed fermentation, according to point 1, relative to altitude 1 (altitude 1 – 774 meters), and point 5, relative to altitude 3 (altitude 3 – 893 meters), differ from the other processes. This confirms the sensory results. This indicates that spontaneous fermentations with water can confer distinct characteristics in the formation of volatile compounds on other processes in higher altitude areas. These two points presented the worst sensory results in the methods with spontaneous water fermentation. In addition, the microorganism can be used as a source of microorganisms to produce yeasts and bacteria, which may be different due to the different areas of altitude (Nielsen, Arneborg, & Jespersen, 2015). Part B (dendrogram Fig. 5) presents the dismemberments of the coffees grouped in the right side of the first dendrogram on the volatile compounds. The first group is G, composed of points 1 and 8, interconnected at altitudes 2 (788 meters) and 4 (907 meters), followed by processes 1 and 4. Sensory-wise, these two processes did not present statistical differences for altitude ranges 1 and 4.
15
Group H has points 11 and 12, both at altitude 5 (1004 meters), with processes 3 and 4. In the sensorial results, these two processes presented the worst results for this altitude range, as seen in the dendrogram shown in Fig. 5. Group I has points 13 and 15, both at altitude 6 (1033 meters), with the connection of processes 1 and 3. Group J has point 16 at altitude 6 (1033 meters), with the connection of process 4, followed by group L, with points 2, 4, 6 and 7, at altitudes 2 and 4, and processes 2, 3 and 4. The best sensory result was also observed in method 1 for this range. Group M has point 3 at altitude 2, with connection of process 3, followed by group N, with point 5, at altitude 4, with connection of process 1. Lastly, group O has points 9, 10 and 14, at altitudes 5 (1004 meters) and 6 (1033 meters), with the connection of processes 1 and 2. The explanation for this chemical and sensory results can be given by the relationship with microorganisms, through the action of yeast and bacteria, which may be different due to the different altitudes (Schwan & Fleet, 2014). The performance of microorganisms to change metabolic pathways may lead to modifications in the structure of fermentation processes (G. V. de M. Pereira et al., 2015). The discussion about the sensory routes through fermentation compared the washed and unwashed coffee, and observed that the volatile profile was different. This shows that washing the coffee altered the final characteristics of the product (Evangelista, Miguel et al., 2014; Evangelista, Silva et al., 2014; Lee et al., 2015; Velmourougane et al., 2011). 3.3 Regression models of the volatile compounds of Arabica coffee Regression models were performed for the following processes: Spontaneous water-washed fermentation; Fully washed fermentation; and Semi-dry fermentation. For the Yeast Fermentation method, no significant regression models were observed for any of the compounds. The first set of results on the regression8 models for washed processes indicate that the following compounds increase linearly with altitude, with the washed method: C8: 5-Methylfurfural
8
Significant at the levels of 5 **% and 1 *% of probability by tests t and F, respectively.
16
(y = 0.0135*x - 4.2732, R² = 0.6835); C14: N-Furfuryl pyrrole (C14: y = 0.0013*x - 0.1335, R² = 0.7481); and C9: 2-Hydroxy-1-methylcyclopenten-3-one (y = 0.003*x - 1.9758, R² = 0.6611*) . Compound 5-methylfurfural has been reported as an important volatile compound for Arabica coffee, with caramel, sweet and spicy characteristics (Petisca, Pérez-Palacios, Farah, Pinho, & Ferreira, 2012; Zheng et al., 2016). Compound N-furfuryl pyran is part of the pyran class. In the case of volatiles, such as furans, pyrroles and thymocytes, it is known that they have strong antioxidant activity and cereal taste characteristics (Asikin et al., 2016). Tressl, Grünewald, Kersten, & Rewicki (1986) have suggested that the formation of N-furfuryl pyran occurs when hydroxyproline reacts with a five-carbon diketone which has been described by the reaction of pentoses with amino acids during heating in the roasting process. N-furfuryl pyran was found in great concentration in both dark, medium and light roast. The formation of N-furfuryl pyran was attributed to the coffees that underwent fermentation induced with microorganisms (yeasts and bacteria) (Lee et al., 2016). Cicloteno, or 2-Hydroxy-1-methylcyclopenten-3-one, which belongs to the group of alcohols, is formed by the Maillard reaction and can be derived from the lactic aldehyde. In this case the cicloteno may have been formed mainly from lactide aldehyde, resulting from oxidation and/or fructose degradation (Cutzach, Chatonnet, & Dubourdieu, 1999). According to Lee et al. (2016), yeast-fermentation coffees have this compound, indicating a relationship between the fermentation and formation of 2-Hydroxy-1-methylcyclopenten-3-one. Again, the reports of Lee et al. (2016) reinforce the thematic about the knowledge of the microorganisms, because this compound is formed by lactic acid from the fermentation process. 3.4 Volatile compounds observed in wet processes with the fully-washed method (dry fermentation): The analysis found significant9 quadratic functional relationships between C8: 5Methylfurfural (y = 0.00007**x2 - 0.1162**x + 55.064) and C12: 2,3-Dihydro-3,5-dihydroxy-6methyl-4H-pyran-4-one (y = 0.0000*5x2 - 0.0958*x + 46.422), with C8 increasing with altitude and
9
Significant at the levels of 5 **% and 1 *% of probability by tests t and F, respectively.
17
C12 decreasing with altitude. The C26: ethyl palmitate (y = 0.00009**x-0.062, R² = 0.8417) increases linearly with altitude with the fully-washed process. These results for the fully-washed dry fermentation indicate the problems related to nonfermentation control (Lee et al., 2016), suggesting that the formation of 2,3-Dihydro-3,5-dihydroxy-6methyl-4H-pyran-4-one can be explained by direct binding to induced fermentation processes (Yu et al., 2013). Finally, it was also verified that the phenolic compound C26: ethyl palmitate increases linearly with altitude with the fully-washed method (dry fermentation). Palmitic acid or ethyl palmitate is reported in the literature as giving rise to fruity attributes in coffee. However, ethyl palmitate was only identified in coffee beans that underwent fermentation (Lee et al., 2016). Detection of ethyl palmitate in fermented green coffees can be attributed to transesterification of triglycerides containing palmitic acid with ethanol or direct esterification of free palmitic acid with ethanol, since palmitic acid is one of the predominant fatty acids in green coffee beans. There is a correlation between special coffees and palmitic acid contents, relating this compound to coffee density, in terms of sensory analysis (Figueiredo et al., 2015). 3.5 Volatile compounds observed in the semi-dry method (without fermentation - peeled): There are significant quadratic10 functional relationships between the phenolic compounds C1: pyridine (y = - 0.0000**7x2 + 0.1358**x - 60.888, R² = 0.9532*), C7: 3(2H)-Furanone, 2,5Dimethyl-3-ethylpyrazine (y = -0.000003**x2 + 0.006**x - 2.3152, R² = 0.949), C8: 5Methylfurfural
(y
=
0.0000*3x2
-
0.0414*x
+
22.94,
R²
=
0.9813*),
C16:
5-
hydroxymethylfuraldehyde (HMF) (y= 0.0043x - 2.177, R² = 0.6984) and C18: 4-ethenyl-3methoxyphenol (y = -0.00007**x2 + 0.123**x - 53.056, R² = 0.9582*). For the compounds C18 and C1, the regression model suggests that both compounds increase with altitude up to approximately 920 meters, and then decrease. Compound C7: 3(2H)-Furanone decreases with altitude, following the same trend as C18: 4ethenyl-3-methoxyphenol, of up to approximately 950 m, then decreasing. Compound C8: 5-
10
Significant at the levels of 5 **% and 1 *% of probability by tests t and F, respectively.
18
Methylfurfural increases with altitude, confirming the condition for its formation is the climate and the type of process that is used for coffee. Finally, it was also verified that the phenolic compound C16: 5-hydroxymethylfuraldeído increases linearly with altitude with the semi-dry method. The volatile compound C7: 3(2H)-Furanone, which is part of the class of furanones, has been characterized as a compound responsible for the formation of a caramel and burnt sugar aroma, emphasizing that this compound transmits such sensory scores. When found in higher concentrations, it becomes fruity, similar to the aroma of raspberries. This compound was only identified in the semi-dry process, which occasionally has a drying process where the mucilage is completely adhered to the parchment, generating a coffee with excess sugars to the parchment, based on the experimental observations in the drying phase of the coffees. Compound C8: 5-Methylfurfural follows the same trend observed for the use of spontaneous waterwashed fermentation . The penultimate compound shown in the regression models was C18: 4-ethenyl-3methoxyphenol or 4-vinylguaiacol. This compound has been described by the degradation of chlorogenic acid. Particularly, 4-ethylguaiacol has a spicy phenolic aroma. According to Lee et al. (2015) the formation of 4-vinyloguaicol, indicates that the presence of Y. lipolytica in the grains of green coffee provided the formation of this compound and that one of the effects of fermentation, such as the generation of volatile phenols (4-vinylguaiacol and 4-vinylphenol), was caused by the fermentative route with the application of Y. lipolytica. In the case of semi-dry processes, the method does not employ the addition of any microorganism other than those already present in the coffee fruit. The occurrence of this volatile was only present in this method, indicating, therefore, that this compound can also be present in coffees that are naturally fermented, from natural microbiota. The volatile compound C16: 5-hydroxymethylfuraldehyde or 5-hydroxymethylfurfural (5HMF), also found, is formed during the food thermal process by acid catalyzed dehydration of reducing sugars and Maillard reaction (Quarta & Anese, 2012). It may initiate the development of antioxidant-related polyphenol compounds as well as Maillard reaction derivatives, such as furosin 19
and hydroxymethylfurfural, which are preferably formed by raising the temperature to certain levels (Asikin et al., 2016). The concentration of 5-HMF decreases significantly with increasing intensity of the roasting condition of 26.8 % (light roast) and drops to 0 % (dark French roasting) (Quarta & Anese, 2012). For the 5-HMF, no significant functional relationships were observed between the compost area and altitude for processes 1, 2 and 3, but for method 4 a significant linear functional relationship was observed between the composite area and altitude variables. The observation regarding the increase of the level of 5-HMF in relation to the altitude for process 4 reinforces the indication that the residual sugars of the parchment can be incorporated to the coffee, due to the sensory observations of the Q-Graders, with the Semi-dry providing softer and sweeter coffees. These results open opportunities for new studies on whether or not the translocation of the sugars present in the pulp to the fruits occurs. More recently the discussion regarding the formation of acrylamide via the HMF pathway has arisen more efficiently than glucose in the reaction of Gökmen, Kocadaǧli, Göncüoǧlu, & Mogol (2012). This indicates that the contribution of HMF and other carbonyls in sugar dehydration should be considered as a potential contributor to the formation of acrylamide and that this compound is a probably a carcinogen. This evidence raises concern from the point of view of food safety, since coffee is a food and priority should be given to processes that avoid risks to human health. According to Akillioglu & Gökmen (2013), the levels of HMF reduction in roasted coffee using yeasts are different in different forms of wet processes. They were able to verify the efficacy of Saccharomyces cerevisiae, a fact that was observed in the results of this study, considering that no significant functional relationships were verified for the Yeast fermentation method in this compound due to altitude. However, for the Semi-dry method a linear functional relationship between compost and altitude was observed. The results indicate that the type of process applied to coffee can be determinant for the formation of some chemical compounds. The positive effects of the fermentation can corroborate with new sensory routes, with the modification of the flavor profile of the coffee, and, consequently, can generate a continuous process 20
that reinforces the quality control in fermented beverages. The variations in the impacts of fermentations with yeast applications on coffee beans may favor changes in the volatiles from different fermentation pathways exhibited by the action of the microorganisms that modified the precursors of the coffee volatiles during the fermentation phase.
4. Conclusion The sensory results, followed by the volatile compounds of the coffee, were altered due to the type of process that is used. For higher altitudes, spontaneous water-washed fermentations or spontaneous semi-dry fermentations were shown to be more promising. The use of yeast culture Saccharomyces cerevisiae resulted in an improvement in coffee quality in the two studied groups with lower altitude, indicating potential for quality improvement through induced fermentation. Regression models for the sensory analysis indicated that the spontaneous water-washed fermentation method has a linear relationship with altitude for all attributes of the SCA protocol. In hotter areas (lower altitudes), the coffees have more woody, cereal and astringent notes to the palate, while in higher-altitude areas, the notes begin to vary with more exotic observations for quality. The environment and process affected the final quality and, consequently, may have influenced the microbial community structures. The next step is to study the microbial community within the fermentation process in the same area.
5. Acknowledgments The authors thank the Federal Institute of Espírito Santo for supporting this research, and the translation and review of this article, as well as the Q-graders, who dedicated themselves to the realization of this study. We also thank the National Council for Scientific and Technological 21
Development - CNPq (469058/2014-5) and Secretariat of Professional and Technological Education of the Ministry of Education - SETEC for making resources available for research.
6. Compliance with ethical standards 6.1 Conflict of Interest The authors declare no conflict of interest.
6.2 Ethical approval This article does not contain any studies with human participants or animals performed by any of
the
authors.
22
7. References Adams, R. P. (2007). Identification of essential oil components by gas chromatography/mass spectroscopy (4th ed.). Allured Pub. Corp. Akillioglu, H. G., & Gökmen, V. (2013). Mitigation of acrylamide and hydroxymethyl furfural in instant coffee by yeast fermentation. Food Research International, 61, 252–256. https://doi.org/10.1016/j.foodres.2013.07.057 Anisa, A., Solomon, W. K., & Solomon, A. (2017). Optimization of roasting time and temperature for brewed hararghe coffee (Coffea Arabica L.) using central composite design. International Food Research Journal, 24(6), 10. Asikin, Y., Hirose, N., Tamaki, H., Ito, S., Oku, H., & Wada, K. (2016). Effects of different dryingsolidification processes on physical properties, volatile fraction, and antioxidant activity of noncentrifugal cane brown sugar. LWT - Food Science and Technology, 66, 340–347. https://doi.org/10.1016/j.lwt.2015.10.039 Borém, F. M., Marques, E. R., & Alves, E. (2008). Ultrastructural analysis of drying damage in parchment
Arabica
coffee
endosperm
cells.
Biosystems
Engineering.
https://doi.org/10.1016/j.biosystemseng.2007.09.027 Bosselmann, A. S., Dons, K., Oberthur, T., Olsen, C. S., Ræbild, A., & Usma, H. (2009). The influence of shade trees on coffee quality in small holder coffee agroforestry systems in Southern Colombia. Agriculture, Ecosystems and Environment, 129(1–3), 253–260. https://doi.org/10.1016/j.agee.2008.09.004 Casas, M. I., Vaughan, M. J., Bonello, P., McSpadden Gardener, B., Grotewold, E., & Alonso, A. P. (2017). Identification of biochemical features of defective Coffea arabica L. beans. Food Research International, 95, 59–67. https://doi.org/10.1016/J.FOODRES.2017.02.015 Ciaramelli, C., Palmioli, A., & Airoldi, C. (2019). Coffee variety, origin and extraction procedure: Implications for coffee beneficial effects on human health. Food Chemistry, 278, 47–55. https://doi.org/10.1016/J.FOODCHEM.2018.11.063 Cutzach, I., Chatonnet, P., & Dubourdieu, D. (1999). Study of the formation mechanisms of some
23
volatile compounds during the aging of sweet fortified wines. Journal of Agricultural and Food Chemistry, 47(7), 2837–2846. https://doi.org/10.1021/jf981224s De Bruyn, F., Zhang, S. J., Pothakos, V., Torres, J., Lambot, C., Moroni, A. V., … De Vuyst, L. (2016). Exploring the impacts of postharvest processing on the microbiota and metabolite profiles during green coffee bean production. Applied and Environmental Microbiology, 83(1), 1–40. https://doi.org/10.1128/AEM.02398-16 Dias, E. C., Borém, F. M., Pereira, R. G. F. A., & Guerreiro, M. C. (2012). Amino acid profiles in unripe Arabica coffee fruits processed using wet and dry methods. European Food Research and Technology, 234(1), 25–32. https://doi.org/10.1007/s00217-011-1607-5 Evangelista, S. R., Miguel, M. G. da C. P., Cordeiro, C. de S., Silva, C. F., Pinheiro, A. C. M., & Schwan, R. F. (2014). Inoculation of starter cultures in a semi-dry coffee (Coffea arabica) fermentation process. Food Microbiology, 44, 87–95. https://doi.org/10.1016/j.fm.2014.05.013 Evangelista, S. R., Silva, C. F., Miguel, M. G. P. da C., Cordeiro, C. de S., Pinheiro, A. C. M., Duarte, W. F., & Schwan, R. F. (2014). Improvement of coffee beverage quality by using selected yeasts strains during the fermentation in dry process. Food Research International, 61, 183–195. https://doi.org/10.1016/j.foodres.2013.11.033 Ferreira, W. P. M., Queiroz, D. M., Silvac, S. A., Tomaz, R. S., & Corrêa, P. C. (2016). Effects of the Orientation of the Mountainside, Altitude and Varieties on the Quality of the Coffee Beverage from the “Matas de Minas” Region, Brazilian Southeast. American Journal of Plant Sciences, 07(08),
1291–1303.
Retrieved
from
http://www.scirp.org/journal/PaperDownload.aspx?DOI=10.4236/ajps.2016.78124 Figueiredo, L. P., Borem, F. M., Ribeiro, F. C., Giomo, G. S., Taveira, J. H. da S., & Malta, M. R. (2015). Fatty acid profiles and parameters of quality of specialty coffees produced in different Brazilian
regions.
African
Journal
of
Agricultural
Research,
10(35),
3484–3493.
https://doi.org/10.5897/AJAR2015.9697 Franca, A. S., Oliveira, L. S., Oliveira, R. C. S., Agresti, P. C. M., & Augusti, R. (2009). A preliminary evaluation of the effect of processing temperature on coffee roasting degree assessment.
Journal
of
Food
Engineering,
92(3),
345–352. 24
https://doi.org/10.1016/j.jfoodeng.2008.12.012 Gökmen, V., Kocadaǧli, T., Göncüoǧlu, N., & Mogol, B. A. (2012). Model studies on the role of 5hydroxymethyl-2-furfural in acrylamide formation from asparagine. Food Chemistry, 132(1), 168–174. https://doi.org/10.1016/j.foodchem.2011.10.048 Joët, T., Laffargue, A., Descroix, F., Doulbeau, S., Bertrand, B., Kochko, A. de, & Dussert, S. (2010). Influence of environmental factors, wet processing and their interactions on the biochemical composition
of
green
Arabica
coffee
beans.
Food
Chemistry,
118,
693–701.
https://doi.org/10.1016/j.foodchem.2009.05.048 Lee, L. W., Cheong, M. W., Curran, P., Yu, B., & Liu, S. Q. (2015). Coffee fermentation and flavor An
intricate
and
delicate
relationship.
Food
Chemistry,
185,
182–191.
https://doi.org/10.1016/j.foodchem.2015.03.124 Lee, L. W., Cheong, M. W., Curran, P., Yu, B., & Liu, S. Q. (2016). Modulation of coffee aroma via the fermentation of green coffee beans with Rhizopus oligosporus: I. Green coffee. Food Chemistry, 211, 916–924. https://doi.org/10.1016/j.foodchem.2016.05.076 Li, J., Wang, S., Liu, H.-Y., Zhou, H., & Fu, Y. (2017). Effective Hydrodeoxygenation of Stearic Acid and Cyperus Esculentus Oil into Liquid Alkanes over Nitrogen-Modified Carbon Nanotube-Supported
Ruthenium
Catalysts.
ChemistrySelect,
2(1),
33–41.
https://doi.org/10.1002/slct.201601658 Martinez, A. E. P. (2013). Estudio de la remoción del mucílago de café a través de fermentación natural. Retrieved from http://ridum.umanizales.edu.co:8080/xmlui/handle/6789/1072 Pereira, G. V. de M., Neto, E., Soccol, V. T., Medeiros, A. B. P., Woiciechowski, A. L., & Soccol, C. R. (2015). Conducting starter culture-controlled fermentations of coffee beans during on-farm wet processing: Growth, metabolic analyses and sensorial effects. Food Research International, 348–356. https://doi.org/10.1016/j.foodres.2015.06.027 Pereira, G. V. de M., Soccol, V. T., Pandey, A., Medeiros, A. B. P., Andrade Lara, J. M. R., Gollo, A. L., & Soccol, C. R. (2014). Isolation, selection and evaluation of yeasts for use in fermentation of coffee beans by the wet process. International Journal of Food Microbiology, 188, 60–66. https://doi.org/10.1016/j.ijfoodmicro.2014.07.008 25
Pereira, L. L., Cardoso, W. S., Guarçoni, R. C., da Fonseca, A. F. A., Moreira, T. R., & Caten, C. S. ten. (2017). The consistency in the sensory analysis of coffees using Q-graders. European Food Research and Technology, 243(9), 1545–1554. https://doi.org/10.1007/s00217-017-2863-9 Petisca, C., Pérez-Palacios, T., Farah, A., Pinho, O., & Ferreira, I. M. P. L. V. O. (2012). Furans and other volatile compounds in ground roasted and espresso coffee using headspace solid-phase microextraction: Effect of roasting speed. Food and Bioproducts Processing, 1–9. https://doi.org/10.1016/j.fbp.2012.10.003 Prezotti, L. C., Gomes, J. A., Dadalto, G. G., & Oliveira, J. A. (2007). Manual de recomendação de calagem e adubação para o Estado do Espírito Santo : 5a aproximação. Vitória: SEEA, Incaper &
CEDAGRO.
Retrieved
from
https://biblioteca.incaper.es.gov.br/busca?b=ad&id=299&biblioteca=vazio&busca=autoria:%22 PREZOTTI,
L.
C.%22&qFacets=autoria:%22PREZOTTI,
L.
C.%22&sort=&paginacao=t&paginaAtual=3 Quarta, B., & Anese, M. (2012). Furfurals removal from roasted coffee powder by vacuum treatment. Food Chemistry, 130(3), 610–614. https://doi.org/10.1016/j.foodchem.2011.07.083 Quintero, G. I. P., & Molina, J. G. E. (2015). Fermentación controlada del café: Tecnología para agregar valor a la calidad. Cenicafé, 1–12. Reinato, C. H. R., Borem, F. M., Cirillo, M. Â., & Oliveira, E. C. (2012). Qualidade do café secado em terreiros com diferentes pavimentações e espessuras de camada. Quality of the coffee dryed on grounds with different surface and thickness layers. Coffee Science, 7(3), 223–237. Rendón, M. Y., Salva, T. de J. G., & Bragagnolo, N. (2014). Impact of chemical changes on the sensory characteristics of coffee beans during storage. Food Chemistry, 147, 279–286. https://doi.org/10.1016/J.FOODCHEM.2013.09.123 Ribeiro, L. S., Ribeiro, D. E., Evangelista, S. R., Miguel, M. G. da C. P., Pinheiro, A. C. M., Borém, F. M., & Schwan, R. F. (2017). Controlled fermentation of semi-dry coffee (Coffea arabica) using starter cultures: A sensory perspective. LWT - Food Science and Technology, 82, 32–38. https://doi.org/10.1016/J.LWT.2017.04.008 SCA. (2008). SCA CUPPING PROTOCOLS. 26
Schwan, R. F., & Fleet, G. H. (2014). Cocoa and Coffee Fermentations. (CRC Press, Ed.) (Tayor & Fr). New York. Somporn, C., Kamtuo, A., Theerakulpisut, P., & Siriamornpun, S. (2012). Effect of shading on yield, sugar content, phenolic acids and antioxidant property of coffee beans (Coffea Arabica L. cv. Catimor) harvested from north-eastern Thailand. Journal of the Science of Food and Agriculture, 92(9), 1956–1963. https://doi.org/10.1002/jsfa.5568 Tressl, R., Grünewald, K. G., Kersten, E., & Rewicki, D. (1986). Formation of Pyrroles and Tetrahydroindolizin-6-ones as Hydroxyproline-Specific Maillard Products from Erythrose and Arabinose.
J.
Agrie.
Food
Chem.,
34,
347–350.
Retrieved
from
Trade.
Retrieved
from
https://pubs.acs.org/sharingguidelines USDA.
(2019).
Coffee:
World
Markets
and
https://apps.fas.usda.gov/psdonline/circulars/coffee.pdf Velmourougane, K. (2013). Impact of natural fermentation on physicochemical, microbiological and cup quality characteristics of Arabica and Robusta coffee. Proceedings of the National Academy of
Sciences
India
Section
B
-
Biological
Sciences,
83(2),
233–239.
https://doi.org/10.1007/s40011-012-0130-1 Velmourougane, K., Bhat, R., Gopinandhan, T. N., & Panneerselvam, P. (2011). Impact of delay in processing on mold development, ochratoxin-A and cup quality in arabica and robusta coffee. World
Journal
of
Microbiology
and
Biotechnology,
27(8),
1809–1816.
https://doi.org/10.1007/s11274-010-0639-5 Yu, X., Zhao, M., Liu, F., Zeng, S., & Hu, J. (2013). Identification of 2,3-dihydro-3,5-dihydroxy-6methyl-4H-pyran-4-one as a strong antioxidant in glucose-histidine Maillard reaction products. Food Research International, 51, 397–403. https://doi.org/10.1016/j.foodres.2012.12.044 Zheng, Y., Sun, B., Zhao, M., Zheng, F., Huang, M., Sun, J., … Li, H. (2016). Characterization of the key odorants in Chinese zhima aroma-type baijiu by gas chromatography-olfactometry, quantitative measurements, aroma recombination, and omission studies. Journal of Agricultural and Food Chemistry, 64(26), 5367–5374. https://doi.org/10.1021/acs.jafc.6b01390
27
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Table 1. Averages of the global characteristic score evaluated in four processing and at six altitudes, followed by regression models. Sensory Results- Global Scores Processing 1 2 3 4 Average
774
Altitude (m) 893 907
788
Average 1004
1033
b 78,67
c
77,13
84,44
a
81,48
a
87,63
a
85,39
a
82,46
a
82,68
ab
79,48
ab
85,11
bc
82,70
b
81,81
ab
82,04
b
79,29
b
84,48
c
83,17
b
81,43
b
83,08 83,06
ab
80,98 80,31
ab
87,09 86,08
ab
82,68 83,48
b
82,46
a
a 80,82
ab
80,03 a
79,60
bc
79,98 a
81,70 80,20
Processing 1 3 Source: the authors.
a
79,23 79,09
Regression equation
R2
y=51,1502+0,034778**x Y=66,8706+0,016170*x
0,8314* 0,6582*
1Means
followed by at least one letter vertically does not differ from one another by the Tukey test at 5% probability. Regression equations of the global score characteristic by six altitudes and respective determination coefficients R2, of four processing. * and ** Significant at the 5% and 1% probability levels by the t and F tests, respectively.
28
•
Spontaneous fermentations are more promising for arabica coffee in higher altitudes.
•
S. cerevisiae resulted in an improvement in coffee quality in lower altitude.
•
Coffees have more woody, cereal and astringent sensorial descriptors in hotter areas.
•
The environment affects the final quality; thus, coffees have an intrinsic quality.
29
30
31
S0308-8146(19)32082-5 https://doi.org/10.1016/j.foodchem.2019.125943 FOCH 125943
To appear in:
Food Chemistry
Received Date: Revised Date: Accepted Date:
15 April 2019 21 October 2019 20 November 2019
Please cite this article as: Pereira, L.L., Guarçoni, R.C., Pinheiro, P.F., Osório, V.M., Pinheiro, C.A., Moreira, T.R., ten Caten, C.S., New propositions about coffee wet processing: Chemical and sensory perspectives, Food Chemistry (2019), doi: https://doi.org/10.1016/j.foodchem.2019.125943
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New propositions about coffee wet processing: Chemical and sensory perspectives Lucas Louzada Pereiraa*, Rogério Carvalho Guarçonib, Patrícia Fontes Pinheiroc, Vanessa Moreira Osórioc, Carlos Alexandre Pinheiroc, Tais Rizzo Moreirad, Carla Schwengber ten Catene aFederal
Institute of Espírito Santo. Department of Food Science. Avenida Elizabeth Minete Perim,
S/N. Bairro São Rafael, Venda Nova do Imigrante, Espírito Santo, Brazil, CEP: 29375-000. E-mail: [email protected], ORCID: 0000-0002-4436-8953. bCapixaba
Institute of Technical Assistance, Research and Extension – INCAPER. Department of
Statistics. Rua Afonso Sarlo, 160 - Bento Ferreira, CEP:29052-010. Vitória, Espírito Santo, Brazil. Email: [email protected]. cFederal
University of Espirito Santo. Department of Chemistry and Physic. Center for Exact, Natural
and Health Sciences. Alto Universitário, sn, Guararema, Alegre, Espírito Santo, Brazil, 29550-000. Email: [email protected], [email protected], [email protected]. dFederal
University of Espirito Santo. Center of Agrarian Sciences and Engineering. Av. Gov.
Lindemberg, 316 - Centro, Jerônimo Monteiro, Espírito Santo, Brazil, 29550-000. E-mail: [email protected], ORCID: 0000-0001-5536-6286. eFederal
University of Rio Grande do Sul - UFRGS *. Graduate Program in Production Engineering.
Av. Osvaldo Aranha, n 99/5º andar, Bom Fim, CEP: 90.035-190 – Porto Alegre, Rio Grande do Sul, Brazil. E-mail: [email protected], [email protected]. *Corresponding author: Lucas Louzada Pereira. E-mail: [email protected]
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Abstract The interactions between edaphoclimatic factors, forms of processing, drying, storage and roasting, directly affect the sensorial results. This study applied four forms of wet-processing in six different altitude strata, aiming to potentiate the final quality of the drink. The final quality of the coffees was measured using the sensory technique and HS-SPME-GC/MS analyses. Results indicate that the use of starter culture in the fermentation phase constitutes a relevant alternative for lower-altitude zones, and that spontaneous fermentations have a higher potential of sensorial results at above 900 meters. In the sequence, the volatile compounds were affected according to the type of processing and the altitude. The compounds in general that contributed the most to the formation of the math models were: 2furylmethanol, octadecanal, 2-acetyl-3-methylpyrazine, 2,3-Dihydro-3,5-dihydroxy-6-methyl-4Hpyran-4-one (DDMP) and caffeine. The positive effects of the fermentation corroborate with new sensory routes, modification of the flavor and volatile compounds, consequently, generating new fermentation strategies.
Keywords:
Arabica
coffee,
Fermentation,
HS-SPME-GC/MS,
Sensory
Analysis.
2
1. Introduction The coffee production chain is complex and has great importance to producer and consumer countries, making it a strategic product for the world economy. Nine million tons of coffee are consumed worldwide each year, according to data from the United States Department of Agriculture (USDA, 2019). Several factors interact and influence production, harvesting, processing, drying, storage and roasting, until they are reflected in the evaluation of the quality of the coffee, both for agronomic and chemical aspects and for microbiology. The coffee quality is established by the level of the property and the processing techniques adopted. The most important operations and that will determine the quality of the final drink happen at the coffee farms (Velmourougane, Bhat, Gopinandhan, & Panneerselvam, 2011). But the roasting is primarily intended to cause chemical changes in the coffee bean resulting in the formation of desirable flavor compounds (Anisa, Solomon, & Solomon, 2017). From a processing perspective, Arabica coffee can be conducted in different ways, according to the post-harvest processing characteristic of each microregion. Usually, there are two ways of processing coffee after harvest: keeping the fruit intact, commonly called natural coffee (dry); or wet processing, which can be understood and unfolded in three ways: removing only the bark and part of the mucilage1, called peeled cherry (PC); removing the bark and mucilage mechanically (without mucilage); or removing the bark mechanically and mucilage by fermentation (pulped) (Reinato, Borem, Cirillo, & Oliveira, 2012). These processes are usually complex; each coffee grower has its variations in methodologies in the post-harvest. Often, there is no agreement and exact standardization for wet processing. The wet-processing technique is widely adopted by several Central American countries, resulting in pulped, peeled or demucilated coffees, with presence of the fermentative phase. Many producers use
The mucilage (mesocarp) is located between the bark and the coffee bean, representing on average 5% of the dry weight of the fruit. According to Borém, Marques, & Alves (2008), the amount of sugars in the mucilage of the mature fruit increases the risk of fermentations, which can compromise the quality of the coffee. 1
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this technique to avoid harmful or phenolic2 fermentation during fruit drying (Dias, Borém, Pereira, & Guerreiro, 2012). In addition to the factors associated with processing, it is known that coffees from higher regions usually receive more expressive notes on flavor, aroma, sweetness and body than coffees from warmer regions, as can be seen the literature (De Bruyn et al., 2016). This factor has been associated to the fact that high temperatures prevent the translocation of some chemical compounds to the fruits (Bosselmann et al., 2009), thus being able to constitute a natural terroir for these micro-regions. The coffees have intrinsic quality, derived from the specific characteristics of the region where they are grown (Ferreira, Queiroz, Silvac, Tomaz, & Corrêa, 2016). This systematic approach researches the coffee ecosystem, contributing to a deeper understanding of coffee processing, and could constitute a state-of-the-art framework for further analyses and subsequent control of this complex biotechnological process (De Bruyn et al., 2016). The effect of microorganisms present in the coffee plant and the post-harvest, such as Debaryomyces, Pichia, Candida, Saccharomyces Kluyverie S. Ceverisiae (G. V. de M. Pereira et al., 2014; Schwan & Fleet, 2014); or filamentous fungi, such as Aspergillus, Penicillium, Fusarium and Trichoderma; as well as bacteria, Lactobacillus, Bacillus, Arthrobacter, Acinetobacter, Klebsiella (Evangelista, Miguel et al., 2014; Evangelista, Silva et al., 2014; Quintero & Molina, 2015; Velmourougane, 2013), can affect the final coffee quality. However, the presence of different microorganisms during coffee fermentation has been get more attention in the literature over the last years (Ribeiro et al., 2017). So the ability of these microorganisms to affect coffee has become an opportunity to optimize the coffee production process (Lee, Cheong, Curran, Yu, & Liu, 2015, 2016). Although altitude is empirically known to have beneficial effects on coffee quality, only a few scientific studies have actually documented these effects (Joët et al., 2010). New perspectives emerged with the aim of potentiating the coffee quality curve through induced fermentation, reinforcing the discussion about fermentation, considering that desirable attributes can be optimized during wet processing (Lee et al., 2015). Phenolic fermentation has been pointed out in scientific studies, through sensory analysis of coffee, as a fermentation phase in which the coffee presents the drink as Riada or Rio, being this one with slight taste of iodoform or phenol by virtue of the repugnant flavor to the palate. 2
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Thus, we observe two hypotheses in this study, the first (i) is that different forms of processing modify the sensorial and chemical structure of the coffee, and the second (ii) is that the altitude acts as a factor that interacts with the process, indicating that certain processes respond better depending on the natural condition of production (terroir).
2. Materials and Methods 2.1 Collection of fruits carrying out the experiments Fruit collection was carried out from June to October 2016 in six properties in areas that have a history of production of specialty coffees according to the Specialty Coffee Association's (SCA) technical quality parameter. According to the SCA, coffee which scores 80 points or above on a 100point scale is graded as a specialty coffee (Figure 1). The fruits presenting 85% of maturation were selected for the via-wet process, and the buoyant and green fruits were discarded, not being considered in the sensory and chemical analysis. The coffee fruits were harvested manually, without any contact with the soil. After harvesting, the fruits were stored in hermetic Grainpro bags and were processed on the same day. 2.2 Experimental design After harvesting, the coffees were taken to the processing unit to be washed in 1000-liter plastic boxes to separate the floating fruits. After washing, the fruits were peeled with the DPMM-04 equipment (coffee peeler), from Pinhalense. The fresh pulp and coffee husk were separated for fermentation and must formulation. The fresh water used in the processing of the coffees in both experiments is in accordance with CONAMA guideline n. 357/2005, which deals with the classification of water bodies (Prezotti, Gomes, Dadalto, & Oliveira, 2007). The raw materials used in the formulation of the musts were composed of coffee pulp, bark from peeling, water and yeast (Saccharomyces cerevisiae). Fifteen kilograms of coffee were harvested per experimental plot in all experiments, and after harvest the fruits were processed according to established procedures. Six points were selected by the authors to develop this study in different places of the state of Espírito Santo.
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Figure 1 shows that the samples came from areas with altitudes of 774 m; 788 m; 893 m; 907 m; 1004 m and 1033 m. The experiments were conducted following a randomized block design with five replicates. The process was composed of fermentation in module washed (fermentation with water), yeast fermentation (fermentation with yeast culture), fully washed fermentation (dry, using peeled and demucilated cherries by means of fermentation), and semi-dry fermentation (peeled and dried with remaining mucilage). All the fermentation processes were developed in the Coffee Analysis and Research Laboratory (LAPC), in controlled process. Fig. 1 (Link text) - Map of the location of the experimental points. Of the four proposed processes, a must was prepared from the patent process BR10201600405313, with yeast culture (Saccharomyces cerevisiae) and coffee husk. The four processes had the following steps: Treatment 1: fermentation of must with water (Washed), 10 kg of peeled cherry coffee (pulp), 5 kg of bark (the husk was collected from the coffee pulp and added to the must) and 5 liters of water; Treatment 2: fermentation of must with yeast starter culture (Saccharomyces cerevisiae – Yeast fermentation) in 1% (p/v4) of must, 10 kg of pulped coffee (pulp) and 5 kg of bark (the husk was collected from the coffee pulp and added to the must), 5 liters of water; Treatment 3: dry fermentation must (Fully washed without yeast), 10 kg of peeled cherry coffee (pulp), and 5 kg of bark (the husk was collected from the coffee pulp and added to the must), without additional water; Treatment 4: 10 kg of peeled cherry coffee (pulp), coffee husked without removal of the mucilage (semidry), without any addition of micro-organisms. For the experiments, musts 1 and 2 received addition of water to the process at the temperature of 38ºC (G. V. de M. Pereira et al., 2015) and remained immersed in fermentation tanks in the processing laboratory of the Federal Institute of Espírito Santo (IFES), Venda Nova do Imigrante Campus, Espírito Santo, Brazil, for 36 hours. Must 3 received only bark originating from
3 4
Patent process deposited with the National Institute of Industrial Property (INPI). Part by volume (quantity of micro-organism as a function of must).
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the wet processing and was in fermentation process for 36 hours. Must 4 was taken to drying in a suspended and covered yard immediately after the debarking process. After the fermentation period, musts 1, 2 and 3 were washed and dried in a suspended and covered yard (African Bad – Up-high system to dry). The coffees were sun dried for a period of 15 to 18 days in a covered suspended system (plastic cover), with an average temperature of 19.54 °C, with a maximum of 45.72 °C (day) and minimum of 9.07 °C (at night). Temperature was monitored by the Arduino Uno R3 system - Bluetooth Module Hc-06 Rs232 - Humidity and Temperature Sensor Dht22 Am2302 - SD card module. 2.3 Sensory analysis via the Specialty Coffee Association protocol The SCA sensory analysis protocol was applied to this study with 6 Q-Graders5. The number of Q-Graders in a sensory panel was initially proposed by L. L. Pereira, Cardoso et al., (2017). The quality of a coffee, once evaluated through the SCA (2013) protocol, is expressed by a centesimal numeric scale. The tasting form provides the possibility of evaluating eleven (11) important attributes to the coffee: Fragrance/Aroma, Uniformity, Clean cup, Sweetness, Flavor, Acidity, Body, Aftertaste, Balance, Overall and Global Score Evaluation. 2.4 Preparation of samples for tasting The samples were prepared in the coffee sensory analysis laboratory of the Federal Institute of Espírito Santo, Venda Nova do Imigrante campus. The roasting process was conducted using the Laboratto TGP-2 roaster with the Agtron-SCA disk set, and the roasting point of these samples was between the colors determined by the # 65 and # 55 disks for special coffees (SCA, 2008). The roasting process was executed 24 hours in advance and the grinding respected the time of 8 hours of rest after roast. All the samples were toasted between 9 and 10 minutes and, after roasting and cooling, the samples remained sealed, according to the sensory analysis methodology established by the SCA. The coffee samples were ground with a Bunn G3 electric grinder, with medium/coarse particle size. Each batch of coffee was tasted with 5 cups, and the optimal concentration of 8.25 grams
5 Q-Grader: Q-Graders are qualified, controlled, and professionally trained coffee tasters at the Coffee Quality Institute (CQI).
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of ground coffee in 150 mL of water was adopted, according to the midpoint of the equilibrium graph optimum for obtaining the Golden Cup (SCA, 2008). The infusion point of water was when the water reached 92-95 ºC. The Q-Graders began the evaluations when the temperature of the cups reached 55 ºC, respecting the time of 4 minutes for tasting after the infusion. 2.5 Analysis of volatile compounds Roasted and ground coffee samples were extracted by HS-SPME-GC/MS (solid phase microextraction using the headspace mode, combined with gas chromatography coupled to mass spectrometry). To do this, 3g of these milled and roasted coffees were weighed into a suitable headspace vial (20 mL glass vial), with a magnetic screw cap and silicone septum, which was subjected to heating at 70 ºC for 30 minutes. The volatiles were collected by HS-SPME using the DVB/CAR/PDMS fiber (Divinylbenzene/Carboxene/Poldimethylsiloxane, 50 μm film thickness) and injected into the gas chromatograph coupled to the QP-PLUS-2010 mass spectrometer Shimadzu. The molten silica capillary column used was Rtx-5MS (30 m in length and 0.25 mm in internal diameter). Helium was used as drag gas, with flux of 1.67 mL/min. The temperature of the injector was 250 °C and the detector 300 °C. The initial column temperature was 40 °C, being programmed to have increments of 3 °C every minute until it reached the maximum temperature of 125 °C where it remained for one minute, then the temperature was increased to 10 °C per minute until reaching the temperature of 245 ºC, which was held for 3 minutes. To determine the chemical constituents, the mass spectra obtained were compared to those of the apparatus library (Wiley7, NIST08), with data from other studies and with the retention indices (Adams, 2007). In order to calculate the retention indices (RI), a mixture of linear alkanes (C8 to C23) was injected into the chromatograph under the same conditions used in the analysis of the coffee volatiles (Franca, Oliveira, Oliveira, Agresti, & Augusti, 2009). 2.6 Statistical analysis For the statistical analysis, a joint analysis of variance of experiments was performed on the sensory results. The means were compared by Tukey’s test considering the level of significance of 5 %, and the regression models were tested by the F-test and the t-test parameters.
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Dendrograms were constructed using the mean Euclidean distance to measure the distances between the 24 points (6 altitudes x 4 processing) of sensory analysis according to Table 1 and gas chromatography data, and the points were grouped by the Hierarchical Full Linking method. The idea is to maximize the homogeneity of objects within groups, while maximizing the heterogeneity between groups. The regression models of the chromatography data were tested by the F-test and the parameters by the t-test. Statistical analysis was performed using the software SPSS version 22.
3. Results and Discussions 3.1 Sensory analysis The results of the global sensory score of the coffees processed in this study are presented in Table 1, where the results obtained by means of the joint analysis of experiments for the sensory characteristic of the coffees studied in the regions between 774 and 1,033 meters of altitude were described, followed by regression models. Table 1 (Link text) - Averages of the global characteristic score evaluated in four processes and at six altitudes, followed by regression models.
All processed coffees obtained special scores when considering the general average of the processing. It is observed, however, that the action of yeast (Saccharomyces cerevisiae) improved coffee quality. Processes 2 and 4 did not present any differences (p<0.05) between themselves at 774 meters of altitude (Table 1). Method 4 is different from all others; the processes for methods 2 and 3 are the same; however, method 3 does not differ from methods 1 and 2; finally, method 1 presents the worst sensory result in a global score, but not different from method 3 (Table 1). The improvement of coffee quality with yeast inoculation in the lower part, as mentioned above, may be associated with microbiota. This result may be associated to the fact that high temperatures prevent the translocation of chemical compounds to the fruits, opening a field for discussion about the microbiota of coffees belonging to warmer areas to the detriment of higher
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zones. In this perspective, it is observed that the action of the crops starters was effective (Evangelista, Miguel et al., 2014; Lee et al., 2015). In the experiment conducted at 788 meters of altitude, processes 2, 3 and 4 did not differ from each other (p<0.05). Method 1 was the one that got the worst sensory results. It was possible to observe a trend in method 2 on the overall score, that is, the yeast culture provides a slight increase in quality in this experimental range. For the experiments conducted at 893 and 907 meters of altitude, processes 1, 2 and 4 did not present differences among themselves (p<0.05); method 3 differed from method 1, but not from the others. The Fully washed method (3) presented the worst sensory results for this altitude. The technique of Fully-washed processing is spreading rapidly based on empirical evidence and without much theoretical scientific support, that is, it is clear and evident that the changes that occur in the fermentation process must be better studied (Schwan & Fleet, 2014). In the experiment conducted at 1004 meters, processes 1 and 4 were not different (p<0.05). Method 2 is not different from method 3 and 4, but method 4 differed from method 3. The processes carried out in this area indicate expressive results on the quality of the coffees, with the highest sensory score among all the experiments: 87.67 for method 1, followed by method 4, with 87.09. The method employed for the yeast Saccharomyces cerevisiae suffered a considerable reduction in the sensory mark, evidencing that the inoculation of starter cultures provided a reduction of the sensory score of coffee in the 1250 meters of altitude range, when compared to the spontaneous fermentation method, in the cerrado region of Minas Gerais (G. V. de M. Pereira et al., 2015). At the altitude of 1033 meters, method 1 differed from all others. The highest sensory scores for this range were observed using the washed-water method, with 85.39 points of global score. This result reinforces the spontaneous fermentation condition. Under these results, it is suggested that spontaneous fermentation may be more favorable for areas above 893 meters, due to the natural microbiota of the coffees, which can be confirmed by the significant linear functional relation between global and altitude, for this method processing technology (Table 1).
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These results reinforce the cut off limit for the use of starter cultures or the more adequate selection of each microorganism, respecting the coffee microbiota, since, during coffee fermentation, the bacteria, yeasts and enzymes will act in the degradation of the mucilage, transforming pectic compounds and sugars into alcoholic and organic acids (Martinez, 2013; Somporn, Kamtuo, Theerakulpisut, & Siriamornpun, 2012). The effects of fermentation during wet processing on the coffee flavor profile are not fully explained and are often neglected, since the literature has argued that the main function of fermentation is the removal of mucilage (Lee et al., 2015). Concomitant to the sensory results according to the process employed, the regression models indicate that water-washed fermentation provided improved coffee quality due to altitude, followed by method 3 (Fully washed), which shows that the microbiota present in the fruits is able to take charge of the fermentative processes and that the fermentative action occurs to solubilize polysaccharides6 that are present in the coffee pulp. Consequently, during the fermentation, microorganisms will act in the degradation of the sugars present in the pulp, creating metabolic routes and different sensorial patterns. This factor corroborates that the wet process method significantly influences the microbial community structures and hence the composition of the final green coffee beans. This systematic approach to the coffee ecosystem contributes to a deeper understanding of coffee processing and subsequent control of this complex biotechnological process (De Bruyn et al., 2016). The hierarchical grouping analysis was performed for all sensory attributes by altitude zones. It suggests the existence of two homogeneous groups in the dendrogram: group A formed by points (altitude / method) from 1 to 8, 10 to 16 and 22 to 24; and group B formed by the other points (9 and 17 to 21) according to Fig. 2. Fig. 2 (Link text) – 24-point Dendrogram (6 altitudes and 4 processes). The separation and formation of the sensory groups through multivariate analysis evidenced that the washed method in three altitude zones agglutinates in Group B, indicating that the best global
Polysaccharides are carbohydrates that by hydrolysis originate a large number of monosaccharides and these are constituted by natural polymers. 6
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scores are in agreement. Point 9 (method 1 - washed - at the third altitude - 893 meters), followed by point 17 (method 1 - washed - at the fifth altitude - 1004 meters), ending with point 21 (method 1 washed - altitude - 1033 meters) have higher notes than all other points. Points 18, 19 and 20 belong to the fifth altitude and are grouped at experimental points with higher altitudes (Fig 2). All the coffees with the lowest global scores are in group A, which does not indicate a trend, as observed in group B for the best coffees. The results suggest that coffee processed only with water, through spontaneous fermentation, known as washed, favored the final quality. The same results were observed by Quintero & Molina (2015), and Rendón, Salva, & Bragagnolo (2014). The formation of group B, through spontaneous fermentation processes, indicates the occurrence and action of natural microorganisms, which can generate qualitative gains in these three areas. This interaction between the environment and global coffee quality has been briefly discussed by Joët et al. (2010), indicating the fact that most of the changes occurring in coffee and processing can be interpreted by physiological processes, as well as the effects of temperature during fruit formation, followed by hypoxic conditions during wet processing, a fact confirmed by Somporn et al. (2012). These compounds that are influenced by the environment (climate) need to be better evidenced. The results show that the method of spontaneous fermentation in the wet-process through the washed method can be more promising than the use of yeasts in zones of higher altitude, respecting the characteristic terroir of each region, and that yeasts, especially the S. cerevisiae, can be applied to areas less favored by natural climatic conditions and that such biotechnological applications can provide quality gains, as evidenced in the construction of sensory routes by Evangelista, Miguel et al. (2014) and Evangelista, Silva et al. (2014). 3.2 Multivariate analysis of volatile compounds In addition to the sensory analyses, the results of the volatile compounds are discussed in this section. In total, 98 compounds were found in all roasted coffees. Of the total volatiles found, 28 were identified. The multivariate analysis using dendrograms was used to understand the results regarding volatile compounds, ending with the regression models observed between processes and altitude for the compounds. 12
Fig. 3 shows the existence of two homogeneous groups: Group A, formed by points (altitude/processes) 1 to 4 and 9 to 12. In sequence, other group, B, formed by the other points. For group A, similarities were observed between all processing at altitudes 1 and 3. Fig. 3 (Link text) – 24-point Dendrogram (6 altitudes and 4 processes) on the volatile compounds observed. Analyzing the results shown in Fig. 3, based on the formation of the groups, it is possible to infer that the experiment located at 774 meters is grouped (1 to 4) with the experiment of the third band at 893 meters (9 to 12); Both have are similar due to their chemical compounds, and their processes. The compounds that contributed the most to the formation of the models were7: C5: 2furylmethanol, with 14.1 %; followed by the compounds C27: octadecanal, with 8.33 %; and C11: 2acetyl-3-methylpyrazine, with 7.61 %; C12: 2,3-Dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP); and C23: caffeine, each 7.61 %. The sweet-caramel-nut-flavored 2-furylmethanol compound was one of the compounds that most contributed to the formation of mathematical models. According to Casas et al. (2017), this is a compound found mainly in immature coffee seeds; however Ciaramelli, Palmioli, & Airoldi (2019) describe that 2-furylmethanol is present in coffee beans when trigonelina is decreased in the roasting process. Aldehyde compounds such as octadecanal are not commonly mentioned as a volatile compound present in coffee. Fatty acids are known as important components that can confer flavor and aroma, but few studies have described the relationship and effect of such compounds on coffee quality (Figueiredo et al., 2015). The logical explanation for the formation of this compound can be given by the hydrogenation of linoleic acid in fatty acids, releasing stearic acid, because the reduced stearic acid releases the octadecanal compound, and then the main reaction pathway occurs with octadecane decarboxylation in heptadecane (Li, Wang, Liu, Zhou, & Fu, 2017).
The volatile compounds are arranged from the letter C, followed by the code referring to the retention time of the sample in the chromatography analysis. 7
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The third compound with higher weight in the dendrogram is classified within the pyrazines group. 2-acetyl-3-methylpyrazine is a volatile compound characterized by a sweet potato aroma and strong presence of nuts and cereals. More than 80 pyrazines have been identified in roasted coffee. Some ketones may subsequently participate in reactions that lead to the formation of pyrazines or Strecker aldehydes. For 2-acetyl-3-methylpyrazine, no significant functional relationships were observed between the signal area of the compound and the altitude for all the process. Compounds such as 2,3-Dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, which belong to the terpene class, have already been described by Lee et al. (2016) as a compound formed by biosynthesis in S. cerevisiae fermentations, and DDMP is described as an antioxidant compound according to Yu, Zhao, Liu, Zeng, & Hu (2013). The metabolites generated by the fermentation may confer some differentiated characteristics to the coffee. The formation of 2,3-Dihydro-3,5-dihydroxy6-methyl-4H-pyran-4-one can be explained by the direct connection with processes of fermentation (Li et al., 2017). This compound has sweet, caramel and nut characteristics. The brown sugars have predominantly caramel flavors and, to a lesser extent, acidic characteristics due to the presence of components such as butanoic acid as well as 3-methylbutanoic acid together with 2,3-Dihydro-3,5dihydroxy-6-methyl-4H-pyran-4-one,
5-methyl-2-pyrazinylmethanol
and
2,5-dimethylpyrazine
(Asikin et al., 2016). Finally, the last volatile compound to contribute relative weight to the dendrogram construction is caffeine, or 1,3,7-trimethylxanthine. The volatilization of caffeine amounts to 3% of its total. The fatty matter and the ethereal oils decompose, to a great extent, within the cell walls. Caffeine is odorless and has a very characteristic bitter taste, contributing with a bitterness that is important to the taste and aroma of coffee. There is a possible correlation between the amount of stearic acid and the climatic conditions in which coffee is planted, which puts in discussion the action of climate in the formation of this acid (Rendón et al., 2014). The presence of this compound has not been readily detected in Arabica coffee. Significant functional relationships between the compost area and the altitude were observed for the dry or Fully-
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washed fermentation method discussed later for 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4one. Of the compounds, 2-furylmethanol, octadecanal, caffeine, 2,5-dimethyl-3-ethylpyrazine, 2acetyl-3-methylpyrazine, 4-ethenyl-3-methoxyphenol and methyl palmitate were the most representative compounds among all coffees (Fig. 4). Fig. 4 (Link text) - General mean of the distribution of volatile compounds of Arabica coffee in all processes and areas of study. The volatile compounds were also grouped due to the altitudes and processing in groups A and B (Fig. 5). Fig. 5 (Link text) - New groupings of volatile compounds due to the altitudes and methods observed in both groups A and B shown in Figure 3. Four homogeneous groups were found: group C, formed by point 1; group D, formed by points 2 to 4; group E, formed by point 5; and finally, group F, formed by points 6 to 8. It was observed that the method of spontaneous washed fermentation, according to point 1, relative to altitude 1 (altitude 1 – 774 meters), and point 5, relative to altitude 3 (altitude 3 – 893 meters), differ from the other processes. This confirms the sensory results. This indicates that spontaneous fermentations with water can confer distinct characteristics in the formation of volatile compounds on other processes in higher altitude areas. These two points presented the worst sensory results in the methods with spontaneous water fermentation. In addition, the microorganism can be used as a source of microorganisms to produce yeasts and bacteria, which may be different due to the different areas of altitude (Nielsen, Arneborg, & Jespersen, 2015). Part B (dendrogram Fig. 5) presents the dismemberments of the coffees grouped in the right side of the first dendrogram on the volatile compounds. The first group is G, composed of points 1 and 8, interconnected at altitudes 2 (788 meters) and 4 (907 meters), followed by processes 1 and 4. Sensory-wise, these two processes did not present statistical differences for altitude ranges 1 and 4.
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Group H has points 11 and 12, both at altitude 5 (1004 meters), with processes 3 and 4. In the sensorial results, these two processes presented the worst results for this altitude range, as seen in the dendrogram shown in Fig. 5. Group I has points 13 and 15, both at altitude 6 (1033 meters), with the connection of processes 1 and 3. Group J has point 16 at altitude 6 (1033 meters), with the connection of process 4, followed by group L, with points 2, 4, 6 and 7, at altitudes 2 and 4, and processes 2, 3 and 4. The best sensory result was also observed in method 1 for this range. Group M has point 3 at altitude 2, with connection of process 3, followed by group N, with point 5, at altitude 4, with connection of process 1. Lastly, group O has points 9, 10 and 14, at altitudes 5 (1004 meters) and 6 (1033 meters), with the connection of processes 1 and 2. The explanation for this chemical and sensory results can be given by the relationship with microorganisms, through the action of yeast and bacteria, which may be different due to the different altitudes (Schwan & Fleet, 2014). The performance of microorganisms to change metabolic pathways may lead to modifications in the structure of fermentation processes (G. V. de M. Pereira et al., 2015). The discussion about the sensory routes through fermentation compared the washed and unwashed coffee, and observed that the volatile profile was different. This shows that washing the coffee altered the final characteristics of the product (Evangelista, Miguel et al., 2014; Evangelista, Silva et al., 2014; Lee et al., 2015; Velmourougane et al., 2011). 3.3 Regression models of the volatile compounds of Arabica coffee Regression models were performed for the following processes: Spontaneous water-washed fermentation; Fully washed fermentation; and Semi-dry fermentation. For the Yeast Fermentation method, no significant regression models were observed for any of the compounds. The first set of results on the regression8 models for washed processes indicate that the following compounds increase linearly with altitude, with the washed method: C8: 5-Methylfurfural
8
Significant at the levels of 5 **% and 1 *% of probability by tests t and F, respectively.
16
(y = 0.0135*x - 4.2732, R² = 0.6835); C14: N-Furfuryl pyrrole (C14: y = 0.0013*x - 0.1335, R² = 0.7481); and C9: 2-Hydroxy-1-methylcyclopenten-3-one (y = 0.003*x - 1.9758, R² = 0.6611*) . Compound 5-methylfurfural has been reported as an important volatile compound for Arabica coffee, with caramel, sweet and spicy characteristics (Petisca, Pérez-Palacios, Farah, Pinho, & Ferreira, 2012; Zheng et al., 2016). Compound N-furfuryl pyran is part of the pyran class. In the case of volatiles, such as furans, pyrroles and thymocytes, it is known that they have strong antioxidant activity and cereal taste characteristics (Asikin et al., 2016). Tressl, Grünewald, Kersten, & Rewicki (1986) have suggested that the formation of N-furfuryl pyran occurs when hydroxyproline reacts with a five-carbon diketone which has been described by the reaction of pentoses with amino acids during heating in the roasting process. N-furfuryl pyran was found in great concentration in both dark, medium and light roast. The formation of N-furfuryl pyran was attributed to the coffees that underwent fermentation induced with microorganisms (yeasts and bacteria) (Lee et al., 2016). Cicloteno, or 2-Hydroxy-1-methylcyclopenten-3-one, which belongs to the group of alcohols, is formed by the Maillard reaction and can be derived from the lactic aldehyde. In this case the cicloteno may have been formed mainly from lactide aldehyde, resulting from oxidation and/or fructose degradation (Cutzach, Chatonnet, & Dubourdieu, 1999). According to Lee et al. (2016), yeast-fermentation coffees have this compound, indicating a relationship between the fermentation and formation of 2-Hydroxy-1-methylcyclopenten-3-one. Again, the reports of Lee et al. (2016) reinforce the thematic about the knowledge of the microorganisms, because this compound is formed by lactic acid from the fermentation process. 3.4 Volatile compounds observed in wet processes with the fully-washed method (dry fermentation): The analysis found significant9 quadratic functional relationships between C8: 5Methylfurfural (y = 0.00007**x2 - 0.1162**x + 55.064) and C12: 2,3-Dihydro-3,5-dihydroxy-6methyl-4H-pyran-4-one (y = 0.0000*5x2 - 0.0958*x + 46.422), with C8 increasing with altitude and
9
Significant at the levels of 5 **% and 1 *% of probability by tests t and F, respectively.
17
C12 decreasing with altitude. The C26: ethyl palmitate (y = 0.00009**x-0.062, R² = 0.8417) increases linearly with altitude with the fully-washed process. These results for the fully-washed dry fermentation indicate the problems related to nonfermentation control (Lee et al., 2016), suggesting that the formation of 2,3-Dihydro-3,5-dihydroxy-6methyl-4H-pyran-4-one can be explained by direct binding to induced fermentation processes (Yu et al., 2013). Finally, it was also verified that the phenolic compound C26: ethyl palmitate increases linearly with altitude with the fully-washed method (dry fermentation). Palmitic acid or ethyl palmitate is reported in the literature as giving rise to fruity attributes in coffee. However, ethyl palmitate was only identified in coffee beans that underwent fermentation (Lee et al., 2016). Detection of ethyl palmitate in fermented green coffees can be attributed to transesterification of triglycerides containing palmitic acid with ethanol or direct esterification of free palmitic acid with ethanol, since palmitic acid is one of the predominant fatty acids in green coffee beans. There is a correlation between special coffees and palmitic acid contents, relating this compound to coffee density, in terms of sensory analysis (Figueiredo et al., 2015). 3.5 Volatile compounds observed in the semi-dry method (without fermentation - peeled): There are significant quadratic10 functional relationships between the phenolic compounds C1: pyridine (y = - 0.0000**7x2 + 0.1358**x - 60.888, R² = 0.9532*), C7: 3(2H)-Furanone, 2,5Dimethyl-3-ethylpyrazine (y = -0.000003**x2 + 0.006**x - 2.3152, R² = 0.949), C8: 5Methylfurfural
(y
=
0.0000*3x2
-
0.0414*x
+
22.94,
R²
=
0.9813*),
C16:
5-
hydroxymethylfuraldehyde (HMF) (y= 0.0043x - 2.177, R² = 0.6984) and C18: 4-ethenyl-3methoxyphenol (y = -0.00007**x2 + 0.123**x - 53.056, R² = 0.9582*). For the compounds C18 and C1, the regression model suggests that both compounds increase with altitude up to approximately 920 meters, and then decrease. Compound C7: 3(2H)-Furanone decreases with altitude, following the same trend as C18: 4ethenyl-3-methoxyphenol, of up to approximately 950 m, then decreasing. Compound C8: 5-
10
Significant at the levels of 5 **% and 1 *% of probability by tests t and F, respectively.
18
Methylfurfural increases with altitude, confirming the condition for its formation is the climate and the type of process that is used for coffee. Finally, it was also verified that the phenolic compound C16: 5-hydroxymethylfuraldeído increases linearly with altitude with the semi-dry method. The volatile compound C7: 3(2H)-Furanone, which is part of the class of furanones, has been characterized as a compound responsible for the formation of a caramel and burnt sugar aroma, emphasizing that this compound transmits such sensory scores. When found in higher concentrations, it becomes fruity, similar to the aroma of raspberries. This compound was only identified in the semi-dry process, which occasionally has a drying process where the mucilage is completely adhered to the parchment, generating a coffee with excess sugars to the parchment, based on the experimental observations in the drying phase of the coffees. Compound C8: 5-Methylfurfural follows the same trend observed for the use of spontaneous waterwashed fermentation . The penultimate compound shown in the regression models was C18: 4-ethenyl-3methoxyphenol or 4-vinylguaiacol. This compound has been described by the degradation of chlorogenic acid. Particularly, 4-ethylguaiacol has a spicy phenolic aroma. According to Lee et al. (2015) the formation of 4-vinyloguaicol, indicates that the presence of Y. lipolytica in the grains of green coffee provided the formation of this compound and that one of the effects of fermentation, such as the generation of volatile phenols (4-vinylguaiacol and 4-vinylphenol), was caused by the fermentative route with the application of Y. lipolytica. In the case of semi-dry processes, the method does not employ the addition of any microorganism other than those already present in the coffee fruit. The occurrence of this volatile was only present in this method, indicating, therefore, that this compound can also be present in coffees that are naturally fermented, from natural microbiota. The volatile compound C16: 5-hydroxymethylfuraldehyde or 5-hydroxymethylfurfural (5HMF), also found, is formed during the food thermal process by acid catalyzed dehydration of reducing sugars and Maillard reaction (Quarta & Anese, 2012). It may initiate the development of antioxidant-related polyphenol compounds as well as Maillard reaction derivatives, such as furosin 19
and hydroxymethylfurfural, which are preferably formed by raising the temperature to certain levels (Asikin et al., 2016). The concentration of 5-HMF decreases significantly with increasing intensity of the roasting condition of 26.8 % (light roast) and drops to 0 % (dark French roasting) (Quarta & Anese, 2012). For the 5-HMF, no significant functional relationships were observed between the compost area and altitude for processes 1, 2 and 3, but for method 4 a significant linear functional relationship was observed between the composite area and altitude variables. The observation regarding the increase of the level of 5-HMF in relation to the altitude for process 4 reinforces the indication that the residual sugars of the parchment can be incorporated to the coffee, due to the sensory observations of the Q-Graders, with the Semi-dry providing softer and sweeter coffees. These results open opportunities for new studies on whether or not the translocation of the sugars present in the pulp to the fruits occurs. More recently the discussion regarding the formation of acrylamide via the HMF pathway has arisen more efficiently than glucose in the reaction of Gökmen, Kocadaǧli, Göncüoǧlu, & Mogol (2012). This indicates that the contribution of HMF and other carbonyls in sugar dehydration should be considered as a potential contributor to the formation of acrylamide and that this compound is a probably a carcinogen. This evidence raises concern from the point of view of food safety, since coffee is a food and priority should be given to processes that avoid risks to human health. According to Akillioglu & Gökmen (2013), the levels of HMF reduction in roasted coffee using yeasts are different in different forms of wet processes. They were able to verify the efficacy of Saccharomyces cerevisiae, a fact that was observed in the results of this study, considering that no significant functional relationships were verified for the Yeast fermentation method in this compound due to altitude. However, for the Semi-dry method a linear functional relationship between compost and altitude was observed. The results indicate that the type of process applied to coffee can be determinant for the formation of some chemical compounds. The positive effects of the fermentation can corroborate with new sensory routes, with the modification of the flavor profile of the coffee, and, consequently, can generate a continuous process 20
that reinforces the quality control in fermented beverages. The variations in the impacts of fermentations with yeast applications on coffee beans may favor changes in the volatiles from different fermentation pathways exhibited by the action of the microorganisms that modified the precursors of the coffee volatiles during the fermentation phase.
4. Conclusion The sensory results, followed by the volatile compounds of the coffee, were altered due to the type of process that is used. For higher altitudes, spontaneous water-washed fermentations or spontaneous semi-dry fermentations were shown to be more promising. The use of yeast culture Saccharomyces cerevisiae resulted in an improvement in coffee quality in the two studied groups with lower altitude, indicating potential for quality improvement through induced fermentation. Regression models for the sensory analysis indicated that the spontaneous water-washed fermentation method has a linear relationship with altitude for all attributes of the SCA protocol. In hotter areas (lower altitudes), the coffees have more woody, cereal and astringent notes to the palate, while in higher-altitude areas, the notes begin to vary with more exotic observations for quality. The environment and process affected the final quality and, consequently, may have influenced the microbial community structures. The next step is to study the microbial community within the fermentation process in the same area.
5. Acknowledgments The authors thank the Federal Institute of Espírito Santo for supporting this research, and the translation and review of this article, as well as the Q-graders, who dedicated themselves to the realization of this study. We also thank the National Council for Scientific and Technological 21
Development - CNPq (469058/2014-5) and Secretariat of Professional and Technological Education of the Ministry of Education - SETEC for making resources available for research.
6. Compliance with ethical standards 6.1 Conflict of Interest The authors declare no conflict of interest.
6.2 Ethical approval This article does not contain any studies with human participants or animals performed by any of
the
authors.
22
7. References Adams, R. P. (2007). Identification of essential oil components by gas chromatography/mass spectroscopy (4th ed.). Allured Pub. Corp. Akillioglu, H. G., & Gökmen, V. (2013). Mitigation of acrylamide and hydroxymethyl furfural in instant coffee by yeast fermentation. Food Research International, 61, 252–256. https://doi.org/10.1016/j.foodres.2013.07.057 Anisa, A., Solomon, W. K., & Solomon, A. (2017). Optimization of roasting time and temperature for brewed hararghe coffee (Coffea Arabica L.) using central composite design. International Food Research Journal, 24(6), 10. Asikin, Y., Hirose, N., Tamaki, H., Ito, S., Oku, H., & Wada, K. (2016). Effects of different dryingsolidification processes on physical properties, volatile fraction, and antioxidant activity of noncentrifugal cane brown sugar. LWT - Food Science and Technology, 66, 340–347. https://doi.org/10.1016/j.lwt.2015.10.039 Borém, F. M., Marques, E. R., & Alves, E. (2008). Ultrastructural analysis of drying damage in parchment
Arabica
coffee
endosperm
cells.
Biosystems
Engineering.
https://doi.org/10.1016/j.biosystemseng.2007.09.027 Bosselmann, A. S., Dons, K., Oberthur, T., Olsen, C. S., Ræbild, A., & Usma, H. (2009). The influence of shade trees on coffee quality in small holder coffee agroforestry systems in Southern Colombia. Agriculture, Ecosystems and Environment, 129(1–3), 253–260. https://doi.org/10.1016/j.agee.2008.09.004 Casas, M. I., Vaughan, M. J., Bonello, P., McSpadden Gardener, B., Grotewold, E., & Alonso, A. P. (2017). Identification of biochemical features of defective Coffea arabica L. beans. Food Research International, 95, 59–67. https://doi.org/10.1016/J.FOODRES.2017.02.015 Ciaramelli, C., Palmioli, A., & Airoldi, C. (2019). Coffee variety, origin and extraction procedure: Implications for coffee beneficial effects on human health. Food Chemistry, 278, 47–55. https://doi.org/10.1016/J.FOODCHEM.2018.11.063 Cutzach, I., Chatonnet, P., & Dubourdieu, D. (1999). Study of the formation mechanisms of some
23
volatile compounds during the aging of sweet fortified wines. Journal of Agricultural and Food Chemistry, 47(7), 2837–2846. https://doi.org/10.1021/jf981224s De Bruyn, F., Zhang, S. J., Pothakos, V., Torres, J., Lambot, C., Moroni, A. V., … De Vuyst, L. (2016). Exploring the impacts of postharvest processing on the microbiota and metabolite profiles during green coffee bean production. Applied and Environmental Microbiology, 83(1), 1–40. https://doi.org/10.1128/AEM.02398-16 Dias, E. C., Borém, F. M., Pereira, R. G. F. A., & Guerreiro, M. C. (2012). Amino acid profiles in unripe Arabica coffee fruits processed using wet and dry methods. European Food Research and Technology, 234(1), 25–32. https://doi.org/10.1007/s00217-011-1607-5 Evangelista, S. R., Miguel, M. G. da C. P., Cordeiro, C. de S., Silva, C. F., Pinheiro, A. C. M., & Schwan, R. F. (2014). Inoculation of starter cultures in a semi-dry coffee (Coffea arabica) fermentation process. Food Microbiology, 44, 87–95. https://doi.org/10.1016/j.fm.2014.05.013 Evangelista, S. R., Silva, C. F., Miguel, M. G. P. da C., Cordeiro, C. de S., Pinheiro, A. C. M., Duarte, W. F., & Schwan, R. F. (2014). Improvement of coffee beverage quality by using selected yeasts strains during the fermentation in dry process. Food Research International, 61, 183–195. https://doi.org/10.1016/j.foodres.2013.11.033 Ferreira, W. P. M., Queiroz, D. M., Silvac, S. A., Tomaz, R. S., & Corrêa, P. C. (2016). Effects of the Orientation of the Mountainside, Altitude and Varieties on the Quality of the Coffee Beverage from the “Matas de Minas” Region, Brazilian Southeast. American Journal of Plant Sciences, 07(08),
1291–1303.
Retrieved
from
http://www.scirp.org/journal/PaperDownload.aspx?DOI=10.4236/ajps.2016.78124 Figueiredo, L. P., Borem, F. M., Ribeiro, F. C., Giomo, G. S., Taveira, J. H. da S., & Malta, M. R. (2015). Fatty acid profiles and parameters of quality of specialty coffees produced in different Brazilian
regions.
African
Journal
of
Agricultural
Research,
10(35),
3484–3493.
https://doi.org/10.5897/AJAR2015.9697 Franca, A. S., Oliveira, L. S., Oliveira, R. C. S., Agresti, P. C. M., & Augusti, R. (2009). A preliminary evaluation of the effect of processing temperature on coffee roasting degree assessment.
Journal
of
Food
Engineering,
92(3),
345–352. 24
https://doi.org/10.1016/j.jfoodeng.2008.12.012 Gökmen, V., Kocadaǧli, T., Göncüoǧlu, N., & Mogol, B. A. (2012). Model studies on the role of 5hydroxymethyl-2-furfural in acrylamide formation from asparagine. Food Chemistry, 132(1), 168–174. https://doi.org/10.1016/j.foodchem.2011.10.048 Joët, T., Laffargue, A., Descroix, F., Doulbeau, S., Bertrand, B., Kochko, A. de, & Dussert, S. (2010). Influence of environmental factors, wet processing and their interactions on the biochemical composition
of
green
Arabica
coffee
beans.
Food
Chemistry,
118,
693–701.
https://doi.org/10.1016/j.foodchem.2009.05.048 Lee, L. W., Cheong, M. W., Curran, P., Yu, B., & Liu, S. Q. (2015). Coffee fermentation and flavor An
intricate
and
delicate
relationship.
Food
Chemistry,
185,
182–191.
https://doi.org/10.1016/j.foodchem.2015.03.124 Lee, L. W., Cheong, M. W., Curran, P., Yu, B., & Liu, S. Q. (2016). Modulation of coffee aroma via the fermentation of green coffee beans with Rhizopus oligosporus: I. Green coffee. Food Chemistry, 211, 916–924. https://doi.org/10.1016/j.foodchem.2016.05.076 Li, J., Wang, S., Liu, H.-Y., Zhou, H., & Fu, Y. (2017). Effective Hydrodeoxygenation of Stearic Acid and Cyperus Esculentus Oil into Liquid Alkanes over Nitrogen-Modified Carbon Nanotube-Supported
Ruthenium
Catalysts.
ChemistrySelect,
2(1),
33–41.
https://doi.org/10.1002/slct.201601658 Martinez, A. E. P. (2013). Estudio de la remoción del mucílago de café a través de fermentación natural. Retrieved from http://ridum.umanizales.edu.co:8080/xmlui/handle/6789/1072 Pereira, G. V. de M., Neto, E., Soccol, V. T., Medeiros, A. B. P., Woiciechowski, A. L., & Soccol, C. R. (2015). Conducting starter culture-controlled fermentations of coffee beans during on-farm wet processing: Growth, metabolic analyses and sensorial effects. Food Research International, 348–356. https://doi.org/10.1016/j.foodres.2015.06.027 Pereira, G. V. de M., Soccol, V. T., Pandey, A., Medeiros, A. B. P., Andrade Lara, J. M. R., Gollo, A. L., & Soccol, C. R. (2014). Isolation, selection and evaluation of yeasts for use in fermentation of coffee beans by the wet process. International Journal of Food Microbiology, 188, 60–66. https://doi.org/10.1016/j.ijfoodmicro.2014.07.008 25
Pereira, L. L., Cardoso, W. S., Guarçoni, R. C., da Fonseca, A. F. A., Moreira, T. R., & Caten, C. S. ten. (2017). The consistency in the sensory analysis of coffees using Q-graders. European Food Research and Technology, 243(9), 1545–1554. https://doi.org/10.1007/s00217-017-2863-9 Petisca, C., Pérez-Palacios, T., Farah, A., Pinho, O., & Ferreira, I. M. P. L. V. O. (2012). Furans and other volatile compounds in ground roasted and espresso coffee using headspace solid-phase microextraction: Effect of roasting speed. Food and Bioproducts Processing, 1–9. https://doi.org/10.1016/j.fbp.2012.10.003 Prezotti, L. C., Gomes, J. A., Dadalto, G. G., & Oliveira, J. A. (2007). Manual de recomendação de calagem e adubação para o Estado do Espírito Santo : 5a aproximação. Vitória: SEEA, Incaper &
CEDAGRO.
Retrieved
from
https://biblioteca.incaper.es.gov.br/busca?b=ad&id=299&biblioteca=vazio&busca=autoria:%22 PREZOTTI,
L.
C.%22&qFacets=autoria:%22PREZOTTI,
L.
C.%22&sort=&paginacao=t&paginaAtual=3 Quarta, B., & Anese, M. (2012). Furfurals removal from roasted coffee powder by vacuum treatment. Food Chemistry, 130(3), 610–614. https://doi.org/10.1016/j.foodchem.2011.07.083 Quintero, G. I. P., & Molina, J. G. E. (2015). Fermentación controlada del café: Tecnología para agregar valor a la calidad. Cenicafé, 1–12. Reinato, C. H. R., Borem, F. M., Cirillo, M. Â., & Oliveira, E. C. (2012). Qualidade do café secado em terreiros com diferentes pavimentações e espessuras de camada. Quality of the coffee dryed on grounds with different surface and thickness layers. Coffee Science, 7(3), 223–237. Rendón, M. Y., Salva, T. de J. G., & Bragagnolo, N. (2014). Impact of chemical changes on the sensory characteristics of coffee beans during storage. Food Chemistry, 147, 279–286. https://doi.org/10.1016/J.FOODCHEM.2013.09.123 Ribeiro, L. S., Ribeiro, D. E., Evangelista, S. R., Miguel, M. G. da C. P., Pinheiro, A. C. M., Borém, F. M., & Schwan, R. F. (2017). Controlled fermentation of semi-dry coffee (Coffea arabica) using starter cultures: A sensory perspective. LWT - Food Science and Technology, 82, 32–38. https://doi.org/10.1016/J.LWT.2017.04.008 SCA. (2008). SCA CUPPING PROTOCOLS. 26
Schwan, R. F., & Fleet, G. H. (2014). Cocoa and Coffee Fermentations. (CRC Press, Ed.) (Tayor & Fr). New York. Somporn, C., Kamtuo, A., Theerakulpisut, P., & Siriamornpun, S. (2012). Effect of shading on yield, sugar content, phenolic acids and antioxidant property of coffee beans (Coffea Arabica L. cv. Catimor) harvested from north-eastern Thailand. Journal of the Science of Food and Agriculture, 92(9), 1956–1963. https://doi.org/10.1002/jsfa.5568 Tressl, R., Grünewald, K. G., Kersten, E., & Rewicki, D. (1986). Formation of Pyrroles and Tetrahydroindolizin-6-ones as Hydroxyproline-Specific Maillard Products from Erythrose and Arabinose.
J.
Agrie.
Food
Chem.,
34,
347–350.
Retrieved
from
Trade.
Retrieved
from
https://pubs.acs.org/sharingguidelines USDA.
(2019).
Coffee:
World
Markets
and
https://apps.fas.usda.gov/psdonline/circulars/coffee.pdf Velmourougane, K. (2013). Impact of natural fermentation on physicochemical, microbiological and cup quality characteristics of Arabica and Robusta coffee. Proceedings of the National Academy of
Sciences
India
Section
B
-
Biological
Sciences,
83(2),
233–239.
https://doi.org/10.1007/s40011-012-0130-1 Velmourougane, K., Bhat, R., Gopinandhan, T. N., & Panneerselvam, P. (2011). Impact of delay in processing on mold development, ochratoxin-A and cup quality in arabica and robusta coffee. World
Journal
of
Microbiology
and
Biotechnology,
27(8),
1809–1816.
https://doi.org/10.1007/s11274-010-0639-5 Yu, X., Zhao, M., Liu, F., Zeng, S., & Hu, J. (2013). Identification of 2,3-dihydro-3,5-dihydroxy-6methyl-4H-pyran-4-one as a strong antioxidant in glucose-histidine Maillard reaction products. Food Research International, 51, 397–403. https://doi.org/10.1016/j.foodres.2012.12.044 Zheng, Y., Sun, B., Zhao, M., Zheng, F., Huang, M., Sun, J., … Li, H. (2016). Characterization of the key odorants in Chinese zhima aroma-type baijiu by gas chromatography-olfactometry, quantitative measurements, aroma recombination, and omission studies. Journal of Agricultural and Food Chemistry, 64(26), 5367–5374. https://doi.org/10.1021/acs.jafc.6b01390
27
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Table 1. Averages of the global characteristic score evaluated in four processing and at six altitudes, followed by regression models. Sensory Results- Global Scores Processing 1 2 3 4 Average
774
Altitude (m) 893 907
788
Average 1004
1033
b 78,67
c
77,13
84,44
a
81,48
a
87,63
a
85,39
a
82,46
a
82,68
ab
79,48
ab
85,11
bc
82,70
b
81,81
ab
82,04
b
79,29
b
84,48
c
83,17
b
81,43
b
83,08 83,06
ab
80,98 80,31
ab
87,09 86,08
ab
82,68 83,48
b
82,46
a
a 80,82
ab
80,03 a
79,60
bc
79,98 a
81,70 80,20
Processing 1 3 Source: the authors.
a
79,23 79,09
Regression equation
R2
y=51,1502+0,034778**x Y=66,8706+0,016170*x
0,8314* 0,6582*
1Means
followed by at least one letter vertically does not differ from one another by the Tukey test at 5% probability. Regression equations of the global score characteristic by six altitudes and respective determination coefficients R2, of four processing. * and ** Significant at the 5% and 1% probability levels by the t and F tests, respectively.
28
•
Spontaneous fermentations are more promising for arabica coffee in higher altitudes.
•
S. cerevisiae resulted in an improvement in coffee quality in lower altitude.
•
Coffees have more woody, cereal and astringent sensorial descriptors in hotter areas.
•
The environment affects the final quality; thus, coffees have an intrinsic quality.
29
30
31