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Pre-harvest studies of buriti (Mauritia flexuosa L.F.), a Brazilian native fruit, for the characterization of ideal harvest point and ripening stages
Scientia Horticulturae 202 (2016) 77–82
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Pre-harvest studies of buriti (Mauritia flexuosa L.F.), a Brazilian native fruit, for the characterization of ideal harvest point and ripening stages Jéssica Tosin Milanez a , Leandro Camargo Neves a,∗ , Paula Monique Carvalho da Silva a , Victorio Jacob Bastos a , Muhammad Shahab b , Ronan Carlos Colombo b , Sergio Ruffo Roberto b a b
Federal University of Roraima, Agricultural Research Center, BR 174 Road Km 12, 69310-270 Boa Vista, RR, Brazil Londrina State University, Agricultural Research Center, Celso Garcia Cid Road, km 380, P.O. Box 10.011, ZIP 86057-970 Londrina, PR, Brazil
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Article history: Received 9 December 2015 Received in revised form 11 February 2016 Accepted 17 February 2016 Keywords: Phenolic compounds Respiration Antioxidant capacity Pectin Climateric fruit
a b s t r a c t The buriti (Mauritia flexuosa) is a native palm tree that abundantly grows in the Brazilian territory, which is characterized by its versatility of uses. However, the lack of information about the ideal harvest point and the description of ripening stages of buriti can be regarded as an obstacle in its better economic use. For that purpose, chemical, functional and morphological characterization of buriti fruit is necessary in order to determine its ripening cycle. Buriti fruits were harvested, during 6 years, in transition savanna/forest, in private farms located at Roraima State, Brazil. Then, fruits were selected and standardized according to their appearance (skin color and plant health) and sanitized. After the selection, fruits were analyzed for various characteristics, including polar and equatorial diameter, fresh mass, pH, total soluble solids, pectin contents, PME and PG enzymatic activity, respiration behavior and functional activity with the evaluation of carotenoids, phenolic compounds and antioxidant activity. The completely randomized design was used as a statistical model in a factorial arrangement. The fruits harvested at 210 and 240 days after anthesis exhibited high antioxidant activity throughout the evaluation period, characterized by the presence of phenolic compounds and carotenoids. However, based on the evaluated variables under the specific conditions, the ideal harvest was at 210 days after anthesis. The high concentration of phenolic compounds and carotenoids in the buriti fruits, and the subsequent high antioxidant activity indicates its good functional potential. Furthermore, based on the ethylene and CO2 levels and the response of fruits to physical and chemical analysis, the buriti can be classified as a climacteric fruit. © 2016 Elsevier B.V. All rights reserved.
1. Introduction The buriti (Mauritia flexuosa L.F.) is considered the most abundant native palm that grows naturally in the Amazonian biome of Brazil, and presents great socio-economic potential due to its extensive use. It is commercially used for the production of nonfood by-products, manufacturing of beverages, as a raw material for
∗ Corresponding author at: Federal University of Roraima, BR 174 Road, Km 12, 69310-270 Boa Vista, RR, Brazil. Fax: +55 95 3627 2573. E-mail addresses: jessicam [email protected] (J.T. Milanez), [email protected], [email protected] (L.C. Neves), [email protected] (P.M.C. da Silva), [email protected] (V.J. Bastos), [email protected] (M. Shahab), [email protected] (R.C. Colombo), [email protected] (S.R. Roberto). http://dx.doi.org/10.1016/j.scienta.2016.02.026 0304-4238/© 2016 Elsevier B.V. All rights reserved.
building houses or as a direct food source of vitamins and minerals. Additionally, it also plays an important role in the conservation strategies of fauna, since its fruit act as a source of food for many birds and mammal species. M. flexuosa is an excellent indicator of poorly drained and waterlogged soils too, as its being linked to the existence of springs and wells (Vieira et al., 2010). The phenological development studies in fruits has been performed in relation to its vegetative and reproductive events, during a specific period of time, and their interrelationship with biotic factors (Silva and Santos, 2008), such as rainfall, temperature and day length (Morellato et al., 2000). These stages are specific moments in the life cycle of the fruit, which often occurs in response to certain environmental fluctuations, and this identification is necessary to classify different stages of plant development, as the determina-
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tion of harvest point and the development of the fruits in different ripening stages. The majority of phenological studies are conducted by comparing plant growth to the specific soil and weather conditions over a specific period of time (Jones et al., 2005; Mandelli et al., 2003). Thus, it is necessary to study and establish specific criteria to recommend an optimum harvest point—main objective of this research, especially with species that have a few or no adaptation to commercial production. In order to show the importance of fruit species from Amazon forest, Brazil, the physical-chemical and functional characterization of buriti fruits can be considered as an accurately tool to find out the optimum harvest point and understand the physiological and visual changes on fruits during ripening. This must contribute to a better agronomic management of the species, including fruit quality estimation. (Matheus and Lopes, 2007; Lazzari, 2011). The time of harvest is one of the main parameters that determines the quality of fruit, both for raw consumption and agroindustrialization, and it is a function of different attributes related to each fruit species. To harvest fruit at the right time, the fruit maturation stage must be accurately determined by using appropriate maturation indices. These indices include physical or chemical measures that undergo noticeable changes during maturation to ensure the production of fruits with qualitative stability in sensory properties and appropriate behavior during storage (Balbino, 2005). For that purpose, this study aimed to evaluate the physiochemical and functional characteristics, and the development of buriti fruit, aiming to identify its ripening cycle and to recommend its ideal harvest.
2. Material and methods Fruits of buriti (M. flexuosa L. F.) were harvested from May to October (during 6 seasons), the rainy season in Roraima State, Amazon, Brazil. The following average weather conditions during that time ocurred: 91.22% RH, maximum temperature 36.02 ◦ C, minimum temperature 33.12 ◦ C and 1985.2 mm rainfall. The production area is located in an environment of transition savannah/forest, on private farms in the municipality of Caracaraí, Roraima state (lat: 01◦ 48 58 N and long 61◦ 07 41 W). Initially, during six consecutive seasons it was randomly selected trees were identified by presenting fruit bunches in full development, where fruits were harvested at 30-day interval. After harvest, the fruits were packed in coolers and taken for analysis at Food Technology Laboratory, Federal University of Roraima. Fruits were then selected and standardized based on the appearance (skin color and health condition). Later, they were sanitized with 30 ppm hypochlorite for 10 min, and then placed under the stand to air-dry at room temperature (24 ± 3 ◦ C and RH 80 ± 5%). The analyses were divided into two groups (non-destructive and destructive), as follows: Non-destructive: fruit diameter (mm), both polar and equatorial, were measured using digital calipers, and fresh fruit weight (g) was calculated using an analytical balance (Bel Engineering) (0.1 mg), at each phenological stage of the fruit development. For quantification of respiration (CO2 and ethylene), fruit samples of approximately 1 kg per replication were placed in airtight containers, each one with a capacity of 1 L, for 1 hour at 22 ± 1 ◦ C. After the specified time period, 5 mL of gaseous medium was collected from each container (treatments) with the help of a hypodermic syringe, for ethylene and CO2 dosing. The ethylene concentration was calculated by gas chromatography using Varian® brand gas chromatograph, model 3300, equipped with a stainless steel column of 1/8 , prepared with Porapak® N and flame
ionization detector. Meanwhile, the concentration of CO2 was measured in Shimadzu CR 950 chromatograph equipped with a thermal conductivity detection system. Standard solutions 100 ppm and 5% were used for ethylene and CO2 , respectively. The results were expressed in mL of CO2 per kg h−1 and L of ethylene per kg−1 h−1 (Instituto Adolfo Lutz, 2008). Destructive: since the pulp was used for the analysis therefore in each phase of the analysis, the pulp was extracted by separating it from the peel and seed. After that, it was triturated in order to obtain a homogenous mass, which was then used for the evaluations of all destructive analysis in triplicate. The pH was measured using a potentiometer with a glass electrode (Instituto Adolfo Lutz, 2008). The total acidity (TA) was calculated by titration of the filtrate (1:5 dilution) with 0.1 N NaOH, according to standard technique established by Instituto Adolfo Lutz (2008) and expressed in mg 100 g−1 of citric acid. The soluble solids content (SS) was evaluated according to the methodology of the Instituto Adolfo Lutz (2008) by using a refractometer (model RT-30 ATC) and the results expressed in ◦ Brix. For analysis of total and soluble pectin, extraction was done according to McCready and Mccoomb (1952) technique, calculated by reaction with carbazole using Bitter and Muir technique (1962). The levels of total and soluble pectin were expressed in percentage of galacturonic acid per 100 g of the pulp. The McCready and Mccoomb (1952) extraction technique was used for the extraction of pectin contents. After that, total and soluble pectin contents were determined by reaction with carbazole, as previous described. The activity of the enzyme pectin methyl esterase (PME) was determined using a method described by Jen and Robinson (1984), and the results were expressed in micromole of NaOH per g min−1 . The activity of the enzyme polygalacturonase (PG) was measured according to Pressey and Avants (1973), and the results were expressed as enzymatic activity unit (UAE) per g min−1 . Total phenolics were calculated according to the methodology described by Wettasinghe and Shahidi (1999). A spectrophotometer (UV/vis) was used for evaluation using the Folin-Ciocalteu reagent (Merck), and gallic acid standard curve. The results were expressed in equivalent gallic acid (mg 100 g−1 ). For the extraction of carotenoids, 0.2 g frozen dried sample of peel and pulp was taken in test tubes covered with aluminum foil, and 10 mL of extraction solution of hexane-acetone (6:4) was added to it. The extract was then shaken in shaker tubes for 1 min. After waiting for 9 min, the extracts were then filtered with cotton and immediately after that, reading were recorded in triplicate using spectrophotometer at 450 nm. -Carotene was used as standard for making the calibration curve. The results were expressed in mg of -carotene per 100 g on dry basis (AOAC, 2010). Antioxidant activity was measured by two methods: ORAC (Ou et al., 2001) with adjustments from Huang et al. (2002), and by DPPH (Brand-Williams et al., 1995). For ORAC method, microplates with fluorescein were used. Samples were analyzed at three dilutions, considering the average as the final ORAC value. The quantification of antioxidant activity was done based on the area under the fluorescence decay curve, as proposed by Prior et al. (2005). Thus, the remaining DPPH at the end of the reaction was determined and quantified using a standard curve of Trolox. The antioxidant activity was expressed either way in Eq Trolox per 100 g. The completely randomized design was used as a statistical model in a factorial arrangement, composed of 6 development stages, in 6 consecutive seasons, divided into 3 repetitions, with 25 sampling units (±1 kg) in each repetition. For measuring the significance of the proposed model, regression analysis was carried out for all the variables using statistical F test at 5% probability level. The results represent the average of 6 consecutive analysis (harvests).
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Fig. 1. Fruit length of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation. Fig. 3. pH and titrable acidity of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
Fig. 2. Fruit mass of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
3. Results and discussion All the data here presented represents an average of 6 seasons of studies.
peratures, the process of fruit dehydration was possibly triggered, thus leading to the slow growth of fruit and eventually resulting in the reduction of fresh fruit weight at end of the experimental period, as shown in Fig. 1. Likewise, Berilli et al. (1962) also mention that the final stage of fruit development in the field is strongly influenced by environmental factors, such as temperature, solar radiation and precipitation, as well as genetic inheritances of each plant material. The fresh weight results of this work are reflected in the data published by Souza et al. (1996), in which buriti fruit presents 21% of pulp, yellow orange color, bittersweet flavor, starchy and oily consistency, including 12% of spongy endocarp, 23% of peel and 44% of seed, weighing between 13 and 20 g. However, by evaluating the percent ratio in this present experiment, it has been observed that the deducted fresh weight of the fruits is lower when compared to the findings of Martins (2010), but in the phenological study of this specie growing under a tropical savanna area of Goiás State, Brazil, the percent ratio recorded stood near to the value mentioned above. 3.2. pH, titratable acidity and total soluble solids
3.1. Polar and equatorial diameter, and fresh weight of the fruit, pulp and seed Although it is hard to define the real fruit development in terms of its size by simply collecting the physical data, nonetheless increase has been observed over the annually 6-month experimental period, and such constant behavior continued until the complete ripening of the fruit at 240 DAA (days after anthesis). The progress of the equatorial diameter showed an increase from 4.73 cm at 90 DAA to 7.23 cm at 240 DAA, and the polar diameter elevated from 3.40 cm at 90 DAA to 4.93 cm 240 DAA, respectively (Fig. 1). This data of equatorial diameter is in accordance with the findings of Lorenzi et al. (2010), the striking feature of ellipsoid-oblong of buriti fruit, which is the most common form as compared to the globular-oblong one. At 90 DAA, the average fruit weight was 31.43 g, in which seeds had a mass of 20.73 g, that is 65.95% of the total fruit weight while the pulp was 10.70 g, that is 34.04% of the total fruit weight (Fig. 2). Endocarp and peel weighed less than 1%. Fruit weight increased until 210 DAA, the time when changes have been observed, average fruit weight recorded at that period was 41.52 g, the seeds accounted for 23.51 g, which represented 56.62% of the fruit, and the pulp was accounted for 18.01 g, that is 43.37% of the total fruit weight. Hence, during the evaluation period, on average, the mass of fruit pulp showed an increase of approximately 41%, while the seeds showed only 11%. It is worth mentioning that during the 6year period of evaluation, reduction was observed in the absolute values of fruit weight, pulp and seed, especially between 210–240 DAA, which may be related to the drastic reduction in local rainfall (average decrease of 23.33%). In addition, due to the high local tem-
During the 5-month period of evaluation every year, a constant increase in the fruit pH was observed from 2.2 at 90 DAA to 3.3 at 240 DAA (Fig. 3). Accordingly, similar value of pH was observed by Canuto et al. (2010) in pulp of ripe buriti (3.5 ± 0.1). In this sense, the level of pH may has been influenced by the changing observed in titratable acidity, which ranged with an average value of 0.02 g of citric acid per 100 g at 90 DAA, reaching up to 0.06 g citric acid per 100 g at 240 DAA. These results indicate the continuous production of organic acids (Fig. 3) during the growth process of the fruit, which may have been used for maintaining their metabolic processes, and according to Oliveira et al. (2003), it might be also the indication of the fruit maturation process. This increasing trend indicates that higher organic acids production was required for the metabolism of the fruit, which favored the acidity of pH. Neves et al. (2015) also mentioned that organic acids could constitute an excellent energy reserve in fruits, precisely for further oxidation during respiratory metabolism. The results of soluble solids are similar to those observed by Castro et al. (2014) (Fig. 4). These authors, when analyzed fresh pulp of buritis produced in different regions, reported soluble solids content in the range of 12.36 and 13.67 Brix, respectively. In this study, which was carried out at its native region, the contents of soluble solids varied from 13.48 at 90 DAA to 14.10 Brix at the end of the 240 DAA. 3.3. Enzymatic activity, total and soluble pectin The increased levels of ethylene and CO2 during the fruit maturation process, indicates the intense metabolic activity, which is a
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Fig. 4. Soluble solids of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
typical characteristic of climacteric fruit such as buriti. According to Bashir and Abu-Goukh (2003), this may have been due to the influence of hydrolytic enzyme activation, which tends to present active role until the climacteric peak and decline after passing this point, also indicating a direct relationship between ethylene synthesis and increased respiration activity and the very enzyme activity itself (Fig. 5). This process here can be characterized by the increasing activity of poligacturonase enzyme, which accounted for 23.73 EAU per g min−1 at 90 DAA and reached up to an average activity of 33.43 EAU per g min−1 at 240 DAA. Regarding the activity of pectin methyl esterase, means ranged from 12.7 EAU per g min−1 to 20.4 EAU per g min−1 , corresponding respectively to 90 and 240 DAA, whereas the enzyme polygalacturonase also showed promising growth. Similarly, peptic compounds were solubilized by the initial action of pectin methyl esterase, which triggered the loosening process of peptide chains, so that the poligacturonase would act on the less polymerized chains. However, it has been observed from the maturation process in this trial that the pulp remained rigid even after full ripening. In such a case, Jiang et al. (2003) pointed out the existence of substances and/or inhibitory conditions that interfere with the actions of pectin methyl esterase, which in turn, negatively affect the polygalacturonase activities, even though the level and activities seem normal. Even though without achieving the fruit softening, increases in total pectin contents was observed to the 180 DAA, due to the action of pectinolytic enzymes such as polygalacturonase and pectin methyl esterase (Fig. 6), whereas, from that point on until the end of the evaluation period, a decrease has been observed. Such situation can be related to the trend observed regarding the behavior of respiration and enzymatic activity, possibly using such substrates as a source of biochemical energy. Due to depolymerization during the developmental and maturation stages of the buriti fruits, the tendency towards producing high levels of soluble
Fig. 5. Activities of Pectinametilesterase (PME) and Poligacturonase (PG) enzymes in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
Fig. 6. Total and soluble pectin in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
pectin was also observed (Fig. 6), from 47.7% galacturonic acid per 100 g of pulp at 90 DAA, where the respiratory activity was further reduced to 51.3% galacturonic acid per 100 g of pulp at 240 DAA, during which the fruits metabolism itself requires the availability of less complexed compounds that are available for respiratory metabolism.
3.4. Respiration activity Regarding respiration activity (Fig. 7), there was a gradual increase in CO2 production with initially observed mean of 16.5 mL of CO2 per kg h−1 at 90 DAA, reaching up to 24.7 mL of CO2 per kg h−1 at the end of evaluations (240 DAA). As for ethylene, the mean increased from 1.40 L of ethylene per kg h−1 at 90 DAA to its maximum (3.90 L of ethylene per kg h−1 at 240 DAA), suggesting a climacteric pattern. Same results have been observed for papaya by Silva et al. (2001), where maximum ethylene emission was recorded simultaneously with the maximum CO2 emission. In this sense, it was observed simultaneously to the increase in respiration, soluble solids contents and acidity also increased, as well as the activity of peptic enzymes and consequently the reduction of total pectin content, thus continuing to the physiological maturation process throughout the experimental period. Another factor that characterized the climatic pattern of buriti fruit is the variation in ethylene production during the development period and maturation. This behavior of respiration distinctively reflects a climacteric fruit pattern, especially when analysing the samples taken at 210 DAA where the highest metabolic intensity was observed. Besides, this period might be considered the ideal period of harvest, due to the superiority regarding the sensory and functional analyses of fruits.
Fig. 7. CO2 and ethylene production in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
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Fig. 8. Phenolic compounds in buriti (Mauritia flexuosa) using two methods of extraction. Means represent 6-year period of evaluation.
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Fig. 9. Total caratenoids in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
3.5. Phenolic compounds, carotenoids and antioxidant activity A positive increase was observed in the levels of phenolic compounds of buriti fruits (Fig. 8), calculated from aqueous extracts and ethanoic acid. At 90 DAA, the means recorded for aqueous extracts and ethanoic acid were 36.5 mg of GAE per 100 g and 14.1 mg of GAE per 100 g, respectively, reaching means of 44.1 mg of GAE per 100 g and 15.1 mg of GAE per 100 g at 150 DAA to the aqueous extract and ethanoic acid, respectively, while at 240 DAA, a slight decrease was observed in the aqueous extract, with means of 42.4 mg of GAE per 100 g and subsequent increase in ethanoic acid of 16.3 mg of GAE per 100 g, respectively, that remained unchanged until the end of the evaluations. It can be noted that, the elevated levels of detected phenolic compounds, when added to the other compounds promote the antioxidant activity. Also, by analyzing the extraction methods, it can be observed that the aqueous extraction method showed better results than ethanoic acid one. It has also been found that, when analyzing the extraction method of such compounds that most part of phenolic compounds are water-soluble, which means that, for this specie, although both methods provide similar trends, the aqueous extraction is more appropriate. Although these means have been obtained using the best extraction method, it can be observed that these phenolic levels are superior to those found by Kuskoski et al. (2005) in ananas (21.7 mg 100 g−1 ), cupuac¸u (20.5 mg 100 g−1 ), passion fruit (20.0 mg 100 g−1 ), sapodilla (13.5 mg 100 g−1 ) and pineapple (38.1 mg 100 g−1 ), and lower to the sugar-apple (81.7 mg 100 g−1 ), soursop (54.8 mg 100 g−1 ), papaya (53.2 mg 100 g−1 ) and umbu fruit (44.6 mg 100 g−1 ). The final concentration of phenolic compounds may have been influenced by various factors, such as fruit maturity, the specie itself, cultural practices, geographical origin, growth stage, harvesting conditions and storage process (Soares et al., 2015). In addition, Burns (2001) stated that phenolic compounds are active elements for the defense against external conditions such as light, temperature and humidity. Therefore, bearing in mind that high temperature can promote the rate of respiration and thus, due to metabolic reactions free radicals are formed, so an increase in the phenolic concentration is expected during the development of the fruit in order to combat reactive compounds generated during respiration. An irregular variation was observed from the analysis of carotenoids (Fig. 9) with an initial mean 28.83 mg 100 mL−1 at 90 DAA, which increased thereafter. According to Silva et al. (2010), this variation may have been observed due to the formation of certain chemical compounds as a result from the hydroxylation of ␣-carotene and -carotene process. Moreover, according to these authors, a conversion process can occur to these carotenoid compounds during the ripening stage, triggering a fruit decrease, because due to their provitamin activities, they can also make vita-
Fig. 10. (a) Antioxidant capacity in buriti (Mauritia flexuosa) using ORAC and DPPH methods under aqueous extraction. Means represent 6-year period of evaluation. (b) Antioxidant capacity in buriti (Mauritia flexuosa) using ORAC and DPPH methods under ethanoic extraction. Means represent 6-year period of evaluation.
min A, which is partly used for the protection of fruit against the antioxidant processes. For the analysis of antioxidant activity (Fig. 10a and b ), the ethanoic extract method showed higher antioxidant activity among used methodologies, indicating better extraction capacity and quantification of antioxidant compounds, which include the phenolic compounds and carotenoids. Similar behavior was observed when the ORAC and DPPH methodologies were assessed under the ethanoic acid extractor, suggesting that the choice of methodology for quantification of antioxidant activity will possibly depend on the work support of laboratory technician. Yet, the best expression of ethanoic extract, suggests that the presence of phenolic compounds, even at a lower concentration, is not enough for a better response of antioxidant activity, which is consistent with the results obtained by Jacobo-Velázquez and Cisneros-Zevallos, 2009, who claim that the presence of phenols not necessarily indicate an optimal response of antioxidant activity, because the extraction technique used for antioxidant compounds is not well-matched to the aqueous extraction method, which demonstrated better accu-
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racy and subsequently, no other substance apart from carotenoid compounds contributed to this high antioxidant activity. 4. Conclusions Considering the ethylene and CO2 levels, as well as the metabolic response of the buriti to such compounds throughout the process of development and maturation, the buriti cultivated in the Amazon region can be classified as climacteric fruit, and its ideal harvest point should be 210 days after anthesis. The presence of adequate phenolic compounds and carotenoids in buriti fruits, and the subsequent high antioxidant activity indicates its good functional potential. Acknowledgements Coordination of Improvement of Higher Education (Capes). National Council for Scientific and Technological Development (CNPq). References AOAC—Association of Official Analytical Chemists, 2010. Official Methods of Analysis, Eighteenth ed. AOAC, Washington. Balbino, J.M.S., 2005. Management of harvesting and post-harvesting of the passion fruit. In: Costa, A.F.S., Costa, A.N. (Eds.), Technologies for Passion Fruit Production. Incaper, Vitória, ES, pp. 153–178. Bashir, H.A., Abu-Goukh, A.-B.A., 2003. Compositional changes during guava fruit ripening. Food Chem. 80, 557–563. Berilli, S.S., Oliveira, J.G., Marinho, A.B., Lyra, G.B., Sousa, E.F., Viana, A.P., Bernardo, S., Bitter, T., Muir, H.M., 1962. A modified uronic acid carbazole reaction. Anal. Biochem. 34, 330–334. Brand-Williams, W., Cuvelier, M.E., Berset, C., 1995. Use of a free radical method to evaluate antioxidant activity. Food Sci. Technol. 28, 25–30. Burns, J., 2001. Extraction of phenolics and changes in antioxidant activity of red wines during vinification. J. Agr. Food Chem. 49, 5797–5808. Canuto, G.A.B., Xavier, A.A.O., Neves, L.C., Benassi, M.T., 2010. Caracterizac¸ão físico-química de polpas de frutos da Amazônia e sua correlac¸ão com a atividade anti-radical livre. Rev. Bras. Frutic. 32, 1196–1205. Castro, D.S., Sousa, E.P., Nunes, J.S., Silva, L.M.M., Moreira, I.S., 2014. Caracterizac¸ão física e físico-química de polpa de buriti (Mauritia flexuosa). Revista Verde 9, 117–120. Huang, D., Ou, B., Hampsch-Woodill, M., Flanagan, J.A., Deemer, E.K., 2002. Development and validation of oxygen radical absorbance capacity assay for lipophilic antioxidants using randomlymethylated B-cyclodextrin as the solubility enhancer. J. Agr. Food Chem. 50, 1815. Instituto Adolfo Lutz, 2008. Normas analíticas do IAL: métodos químicos e físicos para análise de. In: Alimentos, Fifth ed. Instituto Adolfo Lutz, São Paulo. Jacobo-Velázquez, D.A., Cisneros-Zevallos, L., 2009. Correlations of antioxidant activity versus phenolic content revisited: a new approach in data analysis for food and medicinal plants. J. Food Sci. 74, 107–113. Jen, J.J., Robinson, M.L.P., 1984. Pectolytic enzymes in sweet bell peppers (Capsicum annum L.). J. Food Sci. 49, 1085–1087. Jiang, C.M., Wu, M.C., Wu, C.L., Chang, H.M., 2003. Pectinesterase and polygalacturonase activities and textural properties of rubbery papaya (Carica papaya Linn.). J. Food Sci. 68, 1590–1594. Jones, G.V., Duchene, E., Tomasi, D., Yuste, J., Braslavksa, O., Schultz, H., Martinez, C., Boso, S., Kuskoski, E.M., Asuero, G.A., Troncoso, A.M., Mancini Filho, J., Fett, R., 2005. Aplicacion de diversos metodos quimicos para determinar actividad
antioxidante em pulpa de frutos. Ciencia e Tecnologia de Alimentos 25, 726–732. Kuskoski, E.M., Asuero, A.G., Troncoso, A.M., Mancini Filho, J., Fett, R., 2005. Aplicación de diversos métodos químicos para determinar actividad antioxidante em pulpa de frutos. Cien. Tecnol. Aliment. Campinas 25 (4), 726–732. Lazzari, M., 2011. Clima e fenologia de cultivares de pessegueiro (Prunus persica) na Região do Alto e Médio Vale do Uruguai. Tese (Doutorado em agrometeorologia)—Faculdade de agronomia, Universidade Federal do Rio Grande do Sul, Porto Alegre. Lorenzi, H., Noblick, L.R., Kahn, F., Ferreira, E., 2010. Brazilian Flora: Arecaceae (Palm). Instituto Plantarum, Nova Odessa. Mandelli, F., Berlato, A., Tonietto, J., 2003. Estimation de la date de débourment da la vigne dans la Serra Gaúcha, Brésil. Jounal Internacional dés Sciences de la Vigne et du Vin, 37, 229–235. Martins M. L. Fenologia, produc¸ão e pós-colheita de frutos de buriti (Mauritia flexuosa L.f.) em três veredas do Cerrado no Estado de Goiás. 2010. 144 f. Dissertac¸ão (Mestrado em Agronomia: Produc¸ão Vegetal)—Escola de Agronomia e Engenharia de Alimentos, Universidade Federal de Goiás, 2010. Matheus, M.T., Lopes, J.C., 2007. Morfologia de frutos: sementes e plântulas e germinac¸ão de sementes de Erythrina variegata L. Revista Brasileira De Sementes 29, 8–15. McCready, P.M., Mccoomb, E.A., 1952. Estration and determination of total pectic material. Anal. Chem. 24, 1586–1588. Morellato, L.P.C., Talora, D.C., Takahasi, A., Bencke, C.C., Romera, E.C., Zipparro, V.B., 2000. Phenology of Atlantic rain forest trees: a comparative study. Biotropical 32, 811–823. Neves, L.C., da Silva, P.M.C., Lima, C.G.B., Bastos, V.J., Roberto, S.R., 2015. Study to determine the optimum harvest date of Murici (Byrsonima coccolobifolia Kunth.) from quality and functional attributes. Sci. Hortic. 188, 49–56. Oliveira, M.S.P., Couturier, G., Beserra, P., 2003. Biologia da polinizac¸ão da palmeira tucumã (Astrocaryum vulgare Mart.) em Belém-Pará, Brasil. Acta Botanica Brasileira, 17, 343–353. Ou, B., Hampsch-Woodill, M., Prior, R.L., 2001. Development and validation of an improved oxygen radical absorbance capacity assay using fluorescein as the fluorescent. J. Agric. Food Chem. 49, 4619–4629. Pressey, R., Avants, J.K., 1973. Separation and characterization of the exopolygalacturonase and endopolygalacturonase from peaches. Plant Phys. 52, 252–256. Prior, R.L., Wu, X., Schaich, K., 2005. Standardized methods for the determination of antioxidant capacity and phenolics in foods and dietary supplements. J. Agr. Food Chem. 53, 4290–4302. Silva, C.S.P., Santos, M.L., 2008. Comportamento fenológico no evento pós-queima e biologia reprodutiva de Spiranthera odoratissima A. St.-Hil. (Rutaceae). Biotemas, 21, 29–39. Silva, M.L.C., Costa, R.S., Santana, A.S., Koblitz, M.G.B., 2010. Compostos fenólicos: carotenóides e atividade antioxidante em produtos vegetais. Semin.: Ciências Agrárias 31, 669–682. Silva, M.G., Lima, J.A.P., Sthel, M.S., Marin, E., Gatts, C.E.N., Cardoso, S.L., Campostrini, E.M.G., Campos, A.C., Massunaga, M.S.O., Vargast, H., 2001. Ethylene and CO2 emission rates in tropical fruits investigated by infrared absorption techniques. Anal. Sci. 17, 534–537. Soares, M., Welter, L., Kuskoski, E.M., Gonzaga, L., Fett, R., 2015. Compostos fenolicos e atividade antioxidante da casca de uvas niagara e isabel. Revista Brasileira de Fruticultura, 30, 59–64. Souza, A.G.C., Sousa, N.R., Silva, S.E.L., Nunes, C.D.M., Canto, A.C., Cruz, L.A.A., 1996. Fruteiras da Amazônia. EMBRAPA-CPA, Manaus. Vieira, R. F., Agostini-Costa, T. S., Silva, D. B., Sano, S. M., Ferreira, F. R., 2010. Frutas nativas da região Centro-oeste do Brasil. Brasília, DF: Embrapa Informac¸ões Tecnológica, 322 p. Wettasinghe, M., Shahidi, F., 1999. Evening primrose meal: a source of natural antioxidants and scavenger of hydrogen peroxide and oxygen-derived free radicals. J. Agr. Food Chem. 47, 1801–1812.
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Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti
Pre-harvest studies of buriti (Mauritia flexuosa L.F.), a Brazilian native fruit, for the characterization of ideal harvest point and ripening stages Jéssica Tosin Milanez a , Leandro Camargo Neves a,∗ , Paula Monique Carvalho da Silva a , Victorio Jacob Bastos a , Muhammad Shahab b , Ronan Carlos Colombo b , Sergio Ruffo Roberto b a b
Federal University of Roraima, Agricultural Research Center, BR 174 Road Km 12, 69310-270 Boa Vista, RR, Brazil Londrina State University, Agricultural Research Center, Celso Garcia Cid Road, km 380, P.O. Box 10.011, ZIP 86057-970 Londrina, PR, Brazil
a r t i c l e
i n f o
Article history: Received 9 December 2015 Received in revised form 11 February 2016 Accepted 17 February 2016 Keywords: Phenolic compounds Respiration Antioxidant capacity Pectin Climateric fruit
a b s t r a c t The buriti (Mauritia flexuosa) is a native palm tree that abundantly grows in the Brazilian territory, which is characterized by its versatility of uses. However, the lack of information about the ideal harvest point and the description of ripening stages of buriti can be regarded as an obstacle in its better economic use. For that purpose, chemical, functional and morphological characterization of buriti fruit is necessary in order to determine its ripening cycle. Buriti fruits were harvested, during 6 years, in transition savanna/forest, in private farms located at Roraima State, Brazil. Then, fruits were selected and standardized according to their appearance (skin color and plant health) and sanitized. After the selection, fruits were analyzed for various characteristics, including polar and equatorial diameter, fresh mass, pH, total soluble solids, pectin contents, PME and PG enzymatic activity, respiration behavior and functional activity with the evaluation of carotenoids, phenolic compounds and antioxidant activity. The completely randomized design was used as a statistical model in a factorial arrangement. The fruits harvested at 210 and 240 days after anthesis exhibited high antioxidant activity throughout the evaluation period, characterized by the presence of phenolic compounds and carotenoids. However, based on the evaluated variables under the specific conditions, the ideal harvest was at 210 days after anthesis. The high concentration of phenolic compounds and carotenoids in the buriti fruits, and the subsequent high antioxidant activity indicates its good functional potential. Furthermore, based on the ethylene and CO2 levels and the response of fruits to physical and chemical analysis, the buriti can be classified as a climacteric fruit. © 2016 Elsevier B.V. All rights reserved.
1. Introduction The buriti (Mauritia flexuosa L.F.) is considered the most abundant native palm that grows naturally in the Amazonian biome of Brazil, and presents great socio-economic potential due to its extensive use. It is commercially used for the production of nonfood by-products, manufacturing of beverages, as a raw material for
∗ Corresponding author at: Federal University of Roraima, BR 174 Road, Km 12, 69310-270 Boa Vista, RR, Brazil. Fax: +55 95 3627 2573. E-mail addresses: jessicam [email protected] (J.T. Milanez), [email protected], [email protected] (L.C. Neves), [email protected] (P.M.C. da Silva), [email protected] (V.J. Bastos), [email protected] (M. Shahab), [email protected] (R.C. Colombo), [email protected] (S.R. Roberto). http://dx.doi.org/10.1016/j.scienta.2016.02.026 0304-4238/© 2016 Elsevier B.V. All rights reserved.
building houses or as a direct food source of vitamins and minerals. Additionally, it also plays an important role in the conservation strategies of fauna, since its fruit act as a source of food for many birds and mammal species. M. flexuosa is an excellent indicator of poorly drained and waterlogged soils too, as its being linked to the existence of springs and wells (Vieira et al., 2010). The phenological development studies in fruits has been performed in relation to its vegetative and reproductive events, during a specific period of time, and their interrelationship with biotic factors (Silva and Santos, 2008), such as rainfall, temperature and day length (Morellato et al., 2000). These stages are specific moments in the life cycle of the fruit, which often occurs in response to certain environmental fluctuations, and this identification is necessary to classify different stages of plant development, as the determina-
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tion of harvest point and the development of the fruits in different ripening stages. The majority of phenological studies are conducted by comparing plant growth to the specific soil and weather conditions over a specific period of time (Jones et al., 2005; Mandelli et al., 2003). Thus, it is necessary to study and establish specific criteria to recommend an optimum harvest point—main objective of this research, especially with species that have a few or no adaptation to commercial production. In order to show the importance of fruit species from Amazon forest, Brazil, the physical-chemical and functional characterization of buriti fruits can be considered as an accurately tool to find out the optimum harvest point and understand the physiological and visual changes on fruits during ripening. This must contribute to a better agronomic management of the species, including fruit quality estimation. (Matheus and Lopes, 2007; Lazzari, 2011). The time of harvest is one of the main parameters that determines the quality of fruit, both for raw consumption and agroindustrialization, and it is a function of different attributes related to each fruit species. To harvest fruit at the right time, the fruit maturation stage must be accurately determined by using appropriate maturation indices. These indices include physical or chemical measures that undergo noticeable changes during maturation to ensure the production of fruits with qualitative stability in sensory properties and appropriate behavior during storage (Balbino, 2005). For that purpose, this study aimed to evaluate the physiochemical and functional characteristics, and the development of buriti fruit, aiming to identify its ripening cycle and to recommend its ideal harvest.
2. Material and methods Fruits of buriti (M. flexuosa L. F.) were harvested from May to October (during 6 seasons), the rainy season in Roraima State, Amazon, Brazil. The following average weather conditions during that time ocurred: 91.22% RH, maximum temperature 36.02 ◦ C, minimum temperature 33.12 ◦ C and 1985.2 mm rainfall. The production area is located in an environment of transition savannah/forest, on private farms in the municipality of Caracaraí, Roraima state (lat: 01◦ 48 58 N and long 61◦ 07 41 W). Initially, during six consecutive seasons it was randomly selected trees were identified by presenting fruit bunches in full development, where fruits were harvested at 30-day interval. After harvest, the fruits were packed in coolers and taken for analysis at Food Technology Laboratory, Federal University of Roraima. Fruits were then selected and standardized based on the appearance (skin color and health condition). Later, they were sanitized with 30 ppm hypochlorite for 10 min, and then placed under the stand to air-dry at room temperature (24 ± 3 ◦ C and RH 80 ± 5%). The analyses were divided into two groups (non-destructive and destructive), as follows: Non-destructive: fruit diameter (mm), both polar and equatorial, were measured using digital calipers, and fresh fruit weight (g) was calculated using an analytical balance (Bel Engineering) (0.1 mg), at each phenological stage of the fruit development. For quantification of respiration (CO2 and ethylene), fruit samples of approximately 1 kg per replication were placed in airtight containers, each one with a capacity of 1 L, for 1 hour at 22 ± 1 ◦ C. After the specified time period, 5 mL of gaseous medium was collected from each container (treatments) with the help of a hypodermic syringe, for ethylene and CO2 dosing. The ethylene concentration was calculated by gas chromatography using Varian® brand gas chromatograph, model 3300, equipped with a stainless steel column of 1/8 , prepared with Porapak® N and flame
ionization detector. Meanwhile, the concentration of CO2 was measured in Shimadzu CR 950 chromatograph equipped with a thermal conductivity detection system. Standard solutions 100 ppm and 5% were used for ethylene and CO2 , respectively. The results were expressed in mL of CO2 per kg h−1 and L of ethylene per kg−1 h−1 (Instituto Adolfo Lutz, 2008). Destructive: since the pulp was used for the analysis therefore in each phase of the analysis, the pulp was extracted by separating it from the peel and seed. After that, it was triturated in order to obtain a homogenous mass, which was then used for the evaluations of all destructive analysis in triplicate. The pH was measured using a potentiometer with a glass electrode (Instituto Adolfo Lutz, 2008). The total acidity (TA) was calculated by titration of the filtrate (1:5 dilution) with 0.1 N NaOH, according to standard technique established by Instituto Adolfo Lutz (2008) and expressed in mg 100 g−1 of citric acid. The soluble solids content (SS) was evaluated according to the methodology of the Instituto Adolfo Lutz (2008) by using a refractometer (model RT-30 ATC) and the results expressed in ◦ Brix. For analysis of total and soluble pectin, extraction was done according to McCready and Mccoomb (1952) technique, calculated by reaction with carbazole using Bitter and Muir technique (1962). The levels of total and soluble pectin were expressed in percentage of galacturonic acid per 100 g of the pulp. The McCready and Mccoomb (1952) extraction technique was used for the extraction of pectin contents. After that, total and soluble pectin contents were determined by reaction with carbazole, as previous described. The activity of the enzyme pectin methyl esterase (PME) was determined using a method described by Jen and Robinson (1984), and the results were expressed in micromole of NaOH per g min−1 . The activity of the enzyme polygalacturonase (PG) was measured according to Pressey and Avants (1973), and the results were expressed as enzymatic activity unit (UAE) per g min−1 . Total phenolics were calculated according to the methodology described by Wettasinghe and Shahidi (1999). A spectrophotometer (UV/vis) was used for evaluation using the Folin-Ciocalteu reagent (Merck), and gallic acid standard curve. The results were expressed in equivalent gallic acid (mg 100 g−1 ). For the extraction of carotenoids, 0.2 g frozen dried sample of peel and pulp was taken in test tubes covered with aluminum foil, and 10 mL of extraction solution of hexane-acetone (6:4) was added to it. The extract was then shaken in shaker tubes for 1 min. After waiting for 9 min, the extracts were then filtered with cotton and immediately after that, reading were recorded in triplicate using spectrophotometer at 450 nm. -Carotene was used as standard for making the calibration curve. The results were expressed in mg of -carotene per 100 g on dry basis (AOAC, 2010). Antioxidant activity was measured by two methods: ORAC (Ou et al., 2001) with adjustments from Huang et al. (2002), and by DPPH (Brand-Williams et al., 1995). For ORAC method, microplates with fluorescein were used. Samples were analyzed at three dilutions, considering the average as the final ORAC value. The quantification of antioxidant activity was done based on the area under the fluorescence decay curve, as proposed by Prior et al. (2005). Thus, the remaining DPPH at the end of the reaction was determined and quantified using a standard curve of Trolox. The antioxidant activity was expressed either way in Eq Trolox per 100 g. The completely randomized design was used as a statistical model in a factorial arrangement, composed of 6 development stages, in 6 consecutive seasons, divided into 3 repetitions, with 25 sampling units (±1 kg) in each repetition. For measuring the significance of the proposed model, regression analysis was carried out for all the variables using statistical F test at 5% probability level. The results represent the average of 6 consecutive analysis (harvests).
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Fig. 1. Fruit length of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation. Fig. 3. pH and titrable acidity of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
Fig. 2. Fruit mass of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
3. Results and discussion All the data here presented represents an average of 6 seasons of studies.
peratures, the process of fruit dehydration was possibly triggered, thus leading to the slow growth of fruit and eventually resulting in the reduction of fresh fruit weight at end of the experimental period, as shown in Fig. 1. Likewise, Berilli et al. (1962) also mention that the final stage of fruit development in the field is strongly influenced by environmental factors, such as temperature, solar radiation and precipitation, as well as genetic inheritances of each plant material. The fresh weight results of this work are reflected in the data published by Souza et al. (1996), in which buriti fruit presents 21% of pulp, yellow orange color, bittersweet flavor, starchy and oily consistency, including 12% of spongy endocarp, 23% of peel and 44% of seed, weighing between 13 and 20 g. However, by evaluating the percent ratio in this present experiment, it has been observed that the deducted fresh weight of the fruits is lower when compared to the findings of Martins (2010), but in the phenological study of this specie growing under a tropical savanna area of Goiás State, Brazil, the percent ratio recorded stood near to the value mentioned above. 3.2. pH, titratable acidity and total soluble solids
3.1. Polar and equatorial diameter, and fresh weight of the fruit, pulp and seed Although it is hard to define the real fruit development in terms of its size by simply collecting the physical data, nonetheless increase has been observed over the annually 6-month experimental period, and such constant behavior continued until the complete ripening of the fruit at 240 DAA (days after anthesis). The progress of the equatorial diameter showed an increase from 4.73 cm at 90 DAA to 7.23 cm at 240 DAA, and the polar diameter elevated from 3.40 cm at 90 DAA to 4.93 cm 240 DAA, respectively (Fig. 1). This data of equatorial diameter is in accordance with the findings of Lorenzi et al. (2010), the striking feature of ellipsoid-oblong of buriti fruit, which is the most common form as compared to the globular-oblong one. At 90 DAA, the average fruit weight was 31.43 g, in which seeds had a mass of 20.73 g, that is 65.95% of the total fruit weight while the pulp was 10.70 g, that is 34.04% of the total fruit weight (Fig. 2). Endocarp and peel weighed less than 1%. Fruit weight increased until 210 DAA, the time when changes have been observed, average fruit weight recorded at that period was 41.52 g, the seeds accounted for 23.51 g, which represented 56.62% of the fruit, and the pulp was accounted for 18.01 g, that is 43.37% of the total fruit weight. Hence, during the evaluation period, on average, the mass of fruit pulp showed an increase of approximately 41%, while the seeds showed only 11%. It is worth mentioning that during the 6year period of evaluation, reduction was observed in the absolute values of fruit weight, pulp and seed, especially between 210–240 DAA, which may be related to the drastic reduction in local rainfall (average decrease of 23.33%). In addition, due to the high local tem-
During the 5-month period of evaluation every year, a constant increase in the fruit pH was observed from 2.2 at 90 DAA to 3.3 at 240 DAA (Fig. 3). Accordingly, similar value of pH was observed by Canuto et al. (2010) in pulp of ripe buriti (3.5 ± 0.1). In this sense, the level of pH may has been influenced by the changing observed in titratable acidity, which ranged with an average value of 0.02 g of citric acid per 100 g at 90 DAA, reaching up to 0.06 g citric acid per 100 g at 240 DAA. These results indicate the continuous production of organic acids (Fig. 3) during the growth process of the fruit, which may have been used for maintaining their metabolic processes, and according to Oliveira et al. (2003), it might be also the indication of the fruit maturation process. This increasing trend indicates that higher organic acids production was required for the metabolism of the fruit, which favored the acidity of pH. Neves et al. (2015) also mentioned that organic acids could constitute an excellent energy reserve in fruits, precisely for further oxidation during respiratory metabolism. The results of soluble solids are similar to those observed by Castro et al. (2014) (Fig. 4). These authors, when analyzed fresh pulp of buritis produced in different regions, reported soluble solids content in the range of 12.36 and 13.67 Brix, respectively. In this study, which was carried out at its native region, the contents of soluble solids varied from 13.48 at 90 DAA to 14.10 Brix at the end of the 240 DAA. 3.3. Enzymatic activity, total and soluble pectin The increased levels of ethylene and CO2 during the fruit maturation process, indicates the intense metabolic activity, which is a
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Fig. 4. Soluble solids of buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
typical characteristic of climacteric fruit such as buriti. According to Bashir and Abu-Goukh (2003), this may have been due to the influence of hydrolytic enzyme activation, which tends to present active role until the climacteric peak and decline after passing this point, also indicating a direct relationship between ethylene synthesis and increased respiration activity and the very enzyme activity itself (Fig. 5). This process here can be characterized by the increasing activity of poligacturonase enzyme, which accounted for 23.73 EAU per g min−1 at 90 DAA and reached up to an average activity of 33.43 EAU per g min−1 at 240 DAA. Regarding the activity of pectin methyl esterase, means ranged from 12.7 EAU per g min−1 to 20.4 EAU per g min−1 , corresponding respectively to 90 and 240 DAA, whereas the enzyme polygalacturonase also showed promising growth. Similarly, peptic compounds were solubilized by the initial action of pectin methyl esterase, which triggered the loosening process of peptide chains, so that the poligacturonase would act on the less polymerized chains. However, it has been observed from the maturation process in this trial that the pulp remained rigid even after full ripening. In such a case, Jiang et al. (2003) pointed out the existence of substances and/or inhibitory conditions that interfere with the actions of pectin methyl esterase, which in turn, negatively affect the polygalacturonase activities, even though the level and activities seem normal. Even though without achieving the fruit softening, increases in total pectin contents was observed to the 180 DAA, due to the action of pectinolytic enzymes such as polygalacturonase and pectin methyl esterase (Fig. 6), whereas, from that point on until the end of the evaluation period, a decrease has been observed. Such situation can be related to the trend observed regarding the behavior of respiration and enzymatic activity, possibly using such substrates as a source of biochemical energy. Due to depolymerization during the developmental and maturation stages of the buriti fruits, the tendency towards producing high levels of soluble
Fig. 5. Activities of Pectinametilesterase (PME) and Poligacturonase (PG) enzymes in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
Fig. 6. Total and soluble pectin in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
pectin was also observed (Fig. 6), from 47.7% galacturonic acid per 100 g of pulp at 90 DAA, where the respiratory activity was further reduced to 51.3% galacturonic acid per 100 g of pulp at 240 DAA, during which the fruits metabolism itself requires the availability of less complexed compounds that are available for respiratory metabolism.
3.4. Respiration activity Regarding respiration activity (Fig. 7), there was a gradual increase in CO2 production with initially observed mean of 16.5 mL of CO2 per kg h−1 at 90 DAA, reaching up to 24.7 mL of CO2 per kg h−1 at the end of evaluations (240 DAA). As for ethylene, the mean increased from 1.40 L of ethylene per kg h−1 at 90 DAA to its maximum (3.90 L of ethylene per kg h−1 at 240 DAA), suggesting a climacteric pattern. Same results have been observed for papaya by Silva et al. (2001), where maximum ethylene emission was recorded simultaneously with the maximum CO2 emission. In this sense, it was observed simultaneously to the increase in respiration, soluble solids contents and acidity also increased, as well as the activity of peptic enzymes and consequently the reduction of total pectin content, thus continuing to the physiological maturation process throughout the experimental period. Another factor that characterized the climatic pattern of buriti fruit is the variation in ethylene production during the development period and maturation. This behavior of respiration distinctively reflects a climacteric fruit pattern, especially when analysing the samples taken at 210 DAA where the highest metabolic intensity was observed. Besides, this period might be considered the ideal period of harvest, due to the superiority regarding the sensory and functional analyses of fruits.
Fig. 7. CO2 and ethylene production in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
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Fig. 8. Phenolic compounds in buriti (Mauritia flexuosa) using two methods of extraction. Means represent 6-year period of evaluation.
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Fig. 9. Total caratenoids in buriti (Mauritia flexuosa). Means represent 6-year period of evaluation.
3.5. Phenolic compounds, carotenoids and antioxidant activity A positive increase was observed in the levels of phenolic compounds of buriti fruits (Fig. 8), calculated from aqueous extracts and ethanoic acid. At 90 DAA, the means recorded for aqueous extracts and ethanoic acid were 36.5 mg of GAE per 100 g and 14.1 mg of GAE per 100 g, respectively, reaching means of 44.1 mg of GAE per 100 g and 15.1 mg of GAE per 100 g at 150 DAA to the aqueous extract and ethanoic acid, respectively, while at 240 DAA, a slight decrease was observed in the aqueous extract, with means of 42.4 mg of GAE per 100 g and subsequent increase in ethanoic acid of 16.3 mg of GAE per 100 g, respectively, that remained unchanged until the end of the evaluations. It can be noted that, the elevated levels of detected phenolic compounds, when added to the other compounds promote the antioxidant activity. Also, by analyzing the extraction methods, it can be observed that the aqueous extraction method showed better results than ethanoic acid one. It has also been found that, when analyzing the extraction method of such compounds that most part of phenolic compounds are water-soluble, which means that, for this specie, although both methods provide similar trends, the aqueous extraction is more appropriate. Although these means have been obtained using the best extraction method, it can be observed that these phenolic levels are superior to those found by Kuskoski et al. (2005) in ananas (21.7 mg 100 g−1 ), cupuac¸u (20.5 mg 100 g−1 ), passion fruit (20.0 mg 100 g−1 ), sapodilla (13.5 mg 100 g−1 ) and pineapple (38.1 mg 100 g−1 ), and lower to the sugar-apple (81.7 mg 100 g−1 ), soursop (54.8 mg 100 g−1 ), papaya (53.2 mg 100 g−1 ) and umbu fruit (44.6 mg 100 g−1 ). The final concentration of phenolic compounds may have been influenced by various factors, such as fruit maturity, the specie itself, cultural practices, geographical origin, growth stage, harvesting conditions and storage process (Soares et al., 2015). In addition, Burns (2001) stated that phenolic compounds are active elements for the defense against external conditions such as light, temperature and humidity. Therefore, bearing in mind that high temperature can promote the rate of respiration and thus, due to metabolic reactions free radicals are formed, so an increase in the phenolic concentration is expected during the development of the fruit in order to combat reactive compounds generated during respiration. An irregular variation was observed from the analysis of carotenoids (Fig. 9) with an initial mean 28.83 mg 100 mL−1 at 90 DAA, which increased thereafter. According to Silva et al. (2010), this variation may have been observed due to the formation of certain chemical compounds as a result from the hydroxylation of ␣-carotene and -carotene process. Moreover, according to these authors, a conversion process can occur to these carotenoid compounds during the ripening stage, triggering a fruit decrease, because due to their provitamin activities, they can also make vita-
Fig. 10. (a) Antioxidant capacity in buriti (Mauritia flexuosa) using ORAC and DPPH methods under aqueous extraction. Means represent 6-year period of evaluation. (b) Antioxidant capacity in buriti (Mauritia flexuosa) using ORAC and DPPH methods under ethanoic extraction. Means represent 6-year period of evaluation.
min A, which is partly used for the protection of fruit against the antioxidant processes. For the analysis of antioxidant activity (Fig. 10a and b ), the ethanoic extract method showed higher antioxidant activity among used methodologies, indicating better extraction capacity and quantification of antioxidant compounds, which include the phenolic compounds and carotenoids. Similar behavior was observed when the ORAC and DPPH methodologies were assessed under the ethanoic acid extractor, suggesting that the choice of methodology for quantification of antioxidant activity will possibly depend on the work support of laboratory technician. Yet, the best expression of ethanoic extract, suggests that the presence of phenolic compounds, even at a lower concentration, is not enough for a better response of antioxidant activity, which is consistent with the results obtained by Jacobo-Velázquez and Cisneros-Zevallos, 2009, who claim that the presence of phenols not necessarily indicate an optimal response of antioxidant activity, because the extraction technique used for antioxidant compounds is not well-matched to the aqueous extraction method, which demonstrated better accu-
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