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Water blanching conditions on the quality of green asparagus butt segment (Asparagus officinalis L.)
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ScienceDirect Materials Today: Proceedings 18 (2019) 4799–4809
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ICMPC-2019
Water blanching conditions on the quality of green asparagus butt segment (Asparagus officinalis L.) Thi Van Linh Nguyen1,2*, Tan Thanh Vo3,4, Tri Duc Lam3,4, Long Giang Bach3,4 2
1 Faculty of Chemical Engineering and Food Technology , Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam. Centre of Excellence for Authenticity, Risk Assessment and Technology of Food, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam 3 NTT Hi-Tech Institute, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam 4 Center of Excellence for Biochemistry and Natural Products, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam
Abstract The butt segment of asparagus contains numerous nutrients, including various antioxidants. In particular, fibers and several mineral contents are quite high. However, asparagus butt segment quality is reduced in processing. Therefore, research on the asparagus butt segment processing for development of food industry and for the benefit of economic is necessary. Water blanching is a pretreatment method applied in most fruit and vegetable industry today. Water blanching process can inhibit enzyme activity and reduce loss of food quality. However, water blanching can lead to loss of nutrient contents as well as changes in color and texture (sensory values). In this study, the temperature was investigated at 700C, 750C, 800C, 850C, and 900C, and the blanching time was observed at 2, 4, 6, and 8 minutes. We evaluated the effect of blanching conditions through the percent retention of vitamin C, phenolic compounds, antioxidant capacity (DPPH assay), and changes of sensory values. The results show that blanching temperatures from 750C to 850C insignificantly affect quality of asparagus butt segment. However, nutrient contents and sensory values decrease rapidly with the increase of blanching time. When asparagus was blanched at 850C for 4 minutes, the percent retention of vitamin C, phenolic and antioxidant capacity was 74.84% 80.34% and 71.24%, respectively. These results suggested the good blanching conditions for asparagus butt segment processing. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: Asparagus butt segment; Water blanching; Free-radical scavenging ability; Sensory values
1. Introduction Asparagus (Asparagus officinalis L) is classified in Liliaceae family. This plant is rich in nutrients. It is a very good source of protein, vitamins such as vitamin A, vitamin B1, vitamin C, vitamin E, and minerals such as Mg, Ca, P, Fe [1]. Asparagus contains many antioxidant compounds, for example rutin, ascorbic acid, tocopherol, ferulic acid. Rutin is the highest antioxidant compound in asparagus [2]. * Corresponding author. E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
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Moreover, asparagus also contains protodioscin, a substance which is classified in saponin groups that can against cancer cell and decrease cholesterol level in blood [3]. Asparagus is classified as one of the highest antioxidant containing vegetables and the fourth highest total phenolic content in twenty three vegetables which are consumed regularly in America [4]. The benefit of asparagus to human health is very high as asparagus can reduce the damage of brain and heart’s pathology, prevent inflammation of the colon and intestine’s diseases, reduce bleeding, and fortify the capillary walls [5]. Fresh asparagus is consumed in many countries. China, America, Peru, and Mexico are the top four countries consuming asparagus in the world, average over 50.000 tons each year [6]. However, asparagus can be deteriorated easily after being harvested. Consequently, several methods are applied to preserve asparagus such as drying, freezing, and canning. These process will limit a loss after harvesting asparagus, increase economic value because of long trade time [7]. When using green asparagus spears, consumers and producers only use the bud (or tip) and the middle section of the spear for processing and often discard the butt segment (or bottom of the spear) [8] because the butt segment contains insoluble fiber which makes it difficult to use. However, the results of scientific publication show that asparagus butt segments have remarkable nutritional value. Specifically, butt segment contains higher concentration of minerals such as Al and Fe than buds and middle sections [9]. Butt segment has high fiber content, and loss of nutrient contents during storage is low [10]. With suitable technology processing, it is possible to utilize this source of material to create products providing fibers and bioactive ingredients for customers and at the same time create value of the materials which used to be discarded, in food processing. Blanching is a pretreatment method which is applied in most vegetable and fruits processing industry. Nowadays, there are three following blanching methods: hot water blanching, steam blanching, and microwave blanching. Water blanching is the most popular method in manufacturing because it is the simplest and the most economical method. [11]. Normally, the temperature of water blanching generally fluctuates between 700C and 1000C [12]. The main purpose of blanching is to inhibit enzyme activities such as polyphenol oxidase, peroxidase, lipoxygenase, and phenolase [13]. However, the blanching process can change the color, texture, and content of nutrients in materials [14], [15]. A number of studies related to blanching process have been conducted. Muftugil (1986) investigated the effect of different methods on green bean and found that when being water blanched, green bean can remain color better than with other blanching methods [16]. Sotome et al. (2009) found that superheated steam and hot water spray methods can better decrease a loss in color and texture than water blanching on potatoes [17]. Neri et al. (2011) investigated the effect of water blanching and sugar solutions (maltose and trehalose) on the texture of sliced carrots and noticed that the effect of sugar solutions was insignificant in 900C [18]. Vegetable and fruits contain important compounds such as vitamin C and polyphenols. These compounds can prevent cancers and heart diseases [19]. Vitamin C is an essential compound which human can’t synthesis [20]. It is destroyed by pH, temperature, light, oxygen, enzyme, and metal catalyst, so vitamin C content is considered a food quality assessment standard [20]. Polyphenols are a group of natural compounds including flavonoids, tocopherols, coumarins. Polyphenol compounds can better prevent oxidation than antioxidant vitamins [21]. That is the reason why the investigation of the effect of parameters on the quality process of vegetable and fruits such as soybeans [14], potatoes [22], peas [23], sweet green and red pepper fruits [24], and green leafy vegetables [25] needs to evaluate the loss of nutrient contents (vitamin C, polyphenols, etc.). Although nutrient contents are important to a quality product, antioxidant activity is also a worth-caring indicator. Therefore, Ganiyu (2005) when studying the effect of blanching process on quality of green vegetables, has measured both vitamin C, polyphenol, and antioxidant activity. The results proved that vitamin C and antioxidant activity were lost in the blanching process but total polyphenol content increased [26]. However, Dewanto et al. (2002) showed that vitamin C content decreased but antioxidant activity increased during thermal treatment of tomatoes in 880C [27]. Nowadays, research information about water blanching on asparagus is still limited, especially for asparagus butt segments. Particularly, the information about the effect of water blanching process on the quality of asparagus butt segments isn’t available until now. From the problem mentioned above, the aim of this study was to investigate the effect of water blanching process on the quality of green asparagus butt segments. Temperature and time’s water blanching will be investigated and evaluated based on the percentage of retention of ascorbic acid, total polyphenol, and antioxidant capacity as well as the sensory values (color and texture) compared to a fresh sample. From that, we can determine suitable parameters for quality asparagus butt segment processing.
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2. Material and methods 2.1. Chemicals and Reagents Green asparagus spears (Asparagus officinalis) were bought at An Phu Dong market, district 12, Ho Chi Minh City, Viet Nam. Characteristic of these selected asparagus spears were green, and they were not damaged. The green asparagus spears were washed. The butt segments were cut into 5 cm lengths. The asparagus butt segments used in this study were 5.0 ± 0.5 cm cylinder and 0.5 ± 0.2 cm diameter (Fig. 1.).
Fig. 1. Green asparagus material used in the study (before and after cutting)
2.2. Chemicals Folin-Ciocalteu Reagent (FCR), Gallic acid, DPPH (2,2-diphenyl-1-picrylhydrazyl), and Trolox (6-hydroxy2,5,7,8-tetramethylchroman-2-carboxylic acid) were bought at Sigma-Aldrich Chemie, Co Ltd (USA), and 2,6dichlorophenolindophenol (DCPIP) was imported from India. Other chemicals such as distilled water (with pH between 6.5 and 8), metaphosphoric, methanol (99.5% purity), Na2CO3 (99.5% purity), ascorbic acid (99.7% purity) were originated from China. 2.3. Water Blanching Process This study, water blanching was investigated with two important factors of the process which were temperature and time. Experiments were designed by the one-factor-at-a-time method. Five levels of blanching temperature investigated were 70, 75, 80, 85, and 900C, and four levels of experimental blanching time were 2, 4, 6, and 8 minutes. After being blanched, the sample was cooled rapidly in cold water with temperature about 5.00C 0.50C. Then, sample was analyzed to determinate the retention of vitamin C and phenolic compounds as well as the antioxidant capacity (free-radical scavenging ability). 2.4. Analytical method Determination of ascorbic acid Ascorbic acid content in material and in the sample after being blanched will be determined according to AOAC 967.21 based on oxidation of ascorbic acid with 2,6–dichlorophenolindophenol (DCPIP) to dehydroascorbic acid
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and the colorless lenco derivatives [28]. Optimized reaction is at pH between 3 and 4. In this environment, a drop of excess blue DCPIP will make solution turn pink. A 5-gram of the sample was ground and extracted with metaphosphoric acid. A 5 ml of extract was titrated with 2, 6-dichlorophenolindophenol (DCPIP). The titration stopped when a drop of excess blue DCPIP makes solution turn pink in acidic medium and last for 15 seconds. Indophenol solution was titrated with the standard ascorbic acid solution. The ascorbic acid content was expressed in mg per gram of dry matter (mg/g dry matter). Determination of total phenolic content The total phenolic content was measured by the Folin-Ciocalteu colorimetric methods, using gallic acid as a standard and being described previously by Velioglu et al. (1998) [29]. The sample (5-gram) was ground and extracted with distilled water at the ratio of 10:1. The extract was placed at room temperature about 30 minutes and then filtered through Whatman No.1. The residue was extracted twice in the same way. The extracts were taken to the norm and analyzed. Extracts (1 ml) were put in a dark tube and added 1ml Folin- Ciocalteu reagent (diluted 10 times with distilled water) and 1 ml sodium carbonate solution (20% w/v). The sample was placed in dark space before being taken to a photometer at an absorption of 765 nm. The total phenolic content was expressed in mg of gallic acid equivalent per gram of dry matter (mg GAE/g dry matter). Determination of antioxidant capacity by DPPH Antioxidant capacity was measured by scavenging free radical (DPPH) which was performed based on the method described by Braca et al. (2001) [30]. Antioxidant compounds had the ability to scavenge free radicals so it discolor purple in DPPH solution. The sample (5-gram) was ground and extracted with methanol. The diluted extract (0.2 ml) was mixed with 3 ml DPPH solution. The sample was kept in the dark about 30 minutes and then measuring absorbance at 515 nm. The result was expressed by mg of Trolox equivalent per gram of dry matter (mg TE/g dry matter). Sensory evaluation After sample was blanched at different mode, its color and texture will be evaluated compared to a fresh sample. Sensory evaluation was performed by description methods of Li et al. (2006) [31]. The results were expressed by image and sensory description. Analysis of data All experiments were conducted in triplicate. The mean and standard deviation of the results were calculated using Microsoft Excel program (Microsoft Inc., Redmond, WA, USA). Experiment data was analyzed using oneway analysis of variance (ANOVA) test in SPSS program (IBM Company, USA) with the level of significance at 5%. 3. Results and discusstion 3.1. Investigating asparagus material Vitamin C content, total phenolic content, and antioxidant capacity (DPPH) of asparagus in the study were determined. These results were analyzed based on specific segments of an asparagus spear as shown in Table 1. These results showed that nutrient content of butt segment is quite high with 78% of Vitamin C content, 50% of total phenolic content, and 50% of antioxidant capacity of bud segment. Moreover, butt segments also have many other nutrients and minerals which offer essential nourishment to intensify and protect human health [9]. Therefore, removing butt segments in processing to make industrial products causes a big loss of the value of asparagus butt segments. Furthermore, asparagus butt segments provide fiber content (32 g/100g dries) [32]. Fibers has an important role to the human body because fiber can treat and prevent some diseases such as heart disease, obesity, diabetes, intestinal disorders Therefore, butt segment asparagus had many potentials to make products that bring health benefit, for example vegetable powder, nutrient powder, or herbal tea. Table 1. Parameters effect on the essential oil yield Bud segment
Butt segment
Vitamin C content (mg)
1.845 0.150
1.433 0.118
Total phenolic content (mg GAE)
8.423 1.159
4.338 0.430
12.560 0.450
6.564 0.274
Antioxidant capacity (DPPH) (mg TE)
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3.2. Investigating the effect of temperature in water blanching process Effect of blanching temperature on sensory values of asparagus butt segment Table 2 showed color and descriptive texture of asparagus butt segment was blanched at different temperatures. Color and texture are two important factors to evaluate the possibility of consumer acceptance of products. Regarding texture, table 2 showed the changes of the hardness due to blanching temperature changing from 700C to 900C. The higher the temperature is, the softer the texture of asparagus is. The difference in texture was not clear at temperatures of 700C and 800C. During the blanching process, pectin hydrolysis reaction, as well as pectin dissolution, would affect the cell wall and middle lamella leading to change hardness vegetable tend to soften [33]. Anderson et al. (1994) also showed the higher the temperature, the more destroyable the texture and the hardness of the plant cell wall [34]. Abu-ghannam and Crowley (2006) also reported the destruction of texture to happen strongly at temperature of 800C [35]. Table 2. Color and texture of asparagus butt segment in water blanching process at different temperatures Fresh
700C
750C
800C
850C
900C
Texture
Hard
Slightly soft
Slightly soft
Slightly soft
Soft
Very soft
Color
Green
Darker green
Darker green
Darker green
Olive green
Olive yellow green
Image
As for color, the above table also showed the color changes due to blanching temperature changes. From 700C to 80 C, the green color of asparagus become darker than the fresh sample. At temperature below 800C, the polyphenol oxidase activity may not be inhibited. Therefore, polyphenol content in plant cells was converted into o-quinones making asparagus become darker. Begum and Brewer (1996) reported that when asparagus was blanched, the green of asparagus becomes greener than fresh sample, but at the same time, it also becomes yellower [12]. Asparagus segments had yellow green color markedly at 850C and 900C because of the destruction of chlorophyll and free coloring compounds when they were diffused into hot water [33]. Chlorophyll is the main pigment creating the green color of vegetable and is a characteristic indicator of a quality green vegetable. Chlorophyll is destroyed easily by enzyme, pH, oxygen, light, and temperature. Therefore, the destruction of chlorophyll takes place during water blanching process and other processing [36]. Effect of blanching temperature on nutrient compounds (vitamin C and total phenols) Figure 2 showed the retention of ascorbic acid and total polyphenol at different temperatures. When temperature increased, ascorbic acid content tended to decrease and got lowest value at 900C (37.31 % 1.342). However, no significant difference of the percent retention of vitamin C from 700C to 850C with ANOVA test at a level of significance of 0.05. Vitamin C is the essential nutrient for human health. This chemical composition is considered an antioxidant found in most vegetable and fruits. Vitamin C can prevent some cancer diseases [37]. Vitamin C was destroyed because of oxidation reaction under the catalysis, which depends on many factors such as temperature, concentration of oxygen, light, water activity, and catalysts [26]. During the blanching process, the deterioration of vitamin C occurs primarily by temperature and exposure to water. However, there was no significant difference in vitamin C retention at different temperatures between 700C and 850C due to the structural characteristics of the material. Asparagus has a hard structure. At a temperature of 850C, the rate of decomposition of vitamin C was faster, but the structure of asparagus under heat condition, which is softened, leads to more extraction of vitamin C in grinding process compared to harder sample. Zheng and Lu (2011) showed the structure of the materials would 0
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affect the loss of ascorbic acid [11]. Moreover, Olivera also explained the plant tissues were destroyed by high temperature, affecting the extraction of substances from plants [38]. The loss of vitamin C content in vegetable and fruits via blanching process ranging from 32% to 68% was reported by Anchinewhu (1983) [39]. At 900C, Vitamin C content decreased dramatically because the structure of asparagus cells was destroyed leading to increased diffusion of vitamin C into blanching solution. Moreover, the temperature which is too high also accelerates the decomposition of vitamin C.
100 90
Retention (%)
80
a
a
a a
70
a
a a b
60
b
50 b
40 30 20 10 0
Vitamin C Total Phenolic
70 83.59 76.19
75 79.59 76.50
80 80.23 60.95
85 75.92 76.19
90 37.31 59.34
Fig. 2. Green asparagus material used in the study (before and after cutting)
Changes in the percentage of total phenolic retention were also shown in figure 2. Polyphenol retention tended to decrease from 70 to 800C, then increase at 850C, and again decline at 900C. There was no significant difference in the percent retention of polyphenols content at 700C, 750C, and 800C. The loss of phenolic content could be mainly due to the effect of temperature. The higher the temperature was, the more the decomposition was [13]. However, polyphenol content was higher at 850C maybe relate to inhibition of polyphenol oxidase. The decomposition of polyphenol occurs following two mechanisms which are catalysis of enzyme and auto-oxidant. Enzyme polyphenol oxidase (PPO) is responsible for the major mechanism which is the oxidation of polyphenol [40]. PPO is an enzyme which presents in most plant tissues. It is capable of catalyzing the oxidation reaction of monophenolic compounds into o-diphenols and o-dihydroxy into o-quinones [41]. PPO enzyme activity decreases the nutritional and sensory values of fruit and vegetable products [42]. Oxidation of phenolic compounds by PPO is considered to be the main cause of the brown color of many fruits and vegetables [43]. Therefore, inhibition of PPO enzyme is a necessity for the food industry today. There were many studies of temperature effects on PPO enzyme activity [44][41][45]. The inactive temperature of PPO enzyme in vegetable ranges from 700C to 900C [43]. This result showed that depending on the type of vegetables, the ability to inactivate enzyme was varied. Moreover, the higher the temperature is, the faster the inactivation rate is. The polyphenol content decreased sharply at 900C due to the influence of high temperature making polyphenol compounds destroyed.
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Fig. 3. The graph shows the percentage of retaining antioxidant capacity at different blanching temperatures
Effect of blanching temperatureon antioxidant capacity Figure 3 represented the changes in antioxidant capacity during a period of blanching at different temperatures. Antioxidant capacity tended to decrease and reached lowest value at 900C (49.12 % 3.445). There was no significant difference in antioxidant capacity at different temperatures from 700C to 850C. In this research, evaluation of antioxidant capacity was based on free-radical scavenging ability. The antioxidant capacity decreased when the temperature increased due to the decomposition of antioxidant compounds such as vitamin C, total polyphenol, and phytochemicals. The retention of vitamin C and total polyphenol content was lowest at 900C leading to the lowest antioxidant capacity. Jaiswal and Abu-Ghannam (2015) reported that temperature affected insignificantly antioxidant capacity in the blanching process of cabbage [46]. Larrauri et al. (1998) showed that the reduction of free radical scavenging ability increased when temperature increased in the sample processing [47]. 3.3. Investigating the effect of water blanching time Effect of blanching time on sensory values of asparagus butt segment Table 3 showed the changes of color and texture of asparagus butt segment in different periods of time. About texture, the results of table 3 noticed that when time was varied from 2 minutes to 8 minutes, the hardness of asparagus decreased constantly. At 6 minutes and 8 minutes blanching, asparagus released viscous liquid on the skin. The reason is due to the structure of green asparagus which is destroyed strongly at high temperate in a long time. The longer the exposure is, the more destructive the structure of the material gets. Liu and Scanlon (2007) reported that low blanching temperature (below 75 0C) make time had little effect on the structure of materials. However, when blanching at high temperature (over 75 0C), time together with temperature make blanched materials soften [48].
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Table 3. Color and texture of asparagus butt segment at different blanching time periods Fresh
2 minutes
4 minutes
6 minutes
8 minutes
Texture
Hard
Slightly hard
Soft
Soft, less tough, little viscous
Soft, tough, more viscous
Color
Green
darker green
olive green
olive yellow green
yellow green
Image
As for color, the result of table 3 also showed when time was changed from 2 minutes to 8 minutes, the green color of asparagus became more yellow. The green discoloration was due to decomposition of chlorophyll compounds and pigments when exposed to water for a long time. In low temperature, the time insignificantly affects to decomposition of chlorophyll. However, at high temperature, the longer the time is, the more decomposition chlorophyll content gets. This result is similar to Jaiswal et al. (2012). In other words, long blanching time will lead to a decrease of chlorophyll content [33]. Effect of blanching time on nutrient compounds (vitamin C and total phenols)
Fig. 4. The graph shows the percentage of remaining vitamin C and total phenolic content at different blanching time periods
Figure 4 showed the changes in vitamin C and total phenolic content during a period of blanching at different periods of time. Vitamin C content decreased gradually following the increase of time and reached the lowest value at 8-minute period (35.71% ± 6.606). There was no significant difference in vitamin C content between 2 minutes and 4 minutes. Vitamin C is not heat-stable and it is water-soluble, so vitamin C is strongly oxidized by exposure to temperature and water environment for a long time. This finding is similar to the report of Gupta et al. (2008) about the process of water blanching on some tropical leaf vegetables when blanching time increased gradually, the content of vitamin C decreased [25]. The changes in total phenolic were also shown in Figure 4. The percent retention of total phenolic tended to decrease and became lowest at 8 minutes (64.45% ± 0.803). There was no significant difference in total phenolic
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content between 2 minutes and 4 minutes using one-way ANOVA test (p > 0.05). The retention of total polyphenol was high at 2 minutes and 4 minutes due to exposure to temperature and water environment in a short time and the inhibition of polyphenol oxidase enzyme. However, at 6 minutes and 8 minutes blanching, polyphenol content decreased dramatically because the compounds which are contained in asparagus cells strongly released in hot water, and phenolic compounds (instance as flavonoids) were destroyed, which leaded to the changes in color and texture. This result is similar to the report of Amin and Wee (2005) where the total polyphenol content decreased following an increase in blanching time in some type of vegetables such as red cabbage, white cabbage, and mustard cabbage [49]. Effect of blanching time on antioxidant capacity
The percent retention of antioxidant capacity (%)
100
80
74.80a
71.24a
60 44.93b 35.25c
40
20
0 2
4
6
8
Time (min) Fig. 5. The graph shows the percentage of retaining antioxidant capacity at different blanching time periods
Figure 5 represented the changes in antioxidant capacity at different blanching time periods. The longer the blanching time is, the worse the antioxidant capacity gets, and it became lowest at 8 minutes (35.25% ± 3.909). There have been many studies reporting the relationship between the total phenolic content and antioxidant capacity. Velioglu et al. (1998) have proved an interaction between polyphenol content and antioxidant ability in several fruits, cereal, and vegetable [29]. In this case, Vitamin C’s and polyphenols’ decomposition leaded to antioxidant capacity decrease in asparagus. This result is similar to Amin and Wee (2005). In other words, long blanching time will lead to antioxidant decline [49]. 4. Conclusion Water blanching process of green asparagus was investigated for the effect of two important factors include temperature and time. This result showed the temperature from 750C-850C insignificantly affected the quality of green asparagus. However, when blanching from 2 minutes to 8 minutes, blanching process affected strongly on the nutrient contents as well as sensory values of butt segment asparagus. The increase of blanching time made the
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quality of product decrease. When asparagus was blanched at 850C for 4 minutes, polyphenol oxidase may be inhibited, which retained a lot of nutrient content as well as antioxidant capacity. The result of this research will support the processing of products from butt segment asparagus such as green asparagus powder, herbal tea, or nectar from asparagus. Acknowledgements This research was funded by the Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam. References [1] J. S. Negi, P. Singh, G. P. Joshi, M. S. Rawat, V. K. Bisht, Chemical constituents of Asparagus, Pharmacogn Rev., 2010 pp. 215–220. [2] N. Shokuhin, K. Gakkaishi, Evaluation of Antioxidant Determination Activity of Vegetable Extracts and of Some Active Compounds., 1994, pp. 611-618. [3] C. K. Chin and S. A. Garrison, Functional elements from asparagus for human health, Acta Hortic., 2008, pp. 219–225. [4] J. A. Vinson, X. Su, L. Zubik, and P. Bose, Phenol Antioxidant Quantity and Quality in Foods:Fruits, J. Agric. Food Chem., 2001, pp. 5315– 5321. [5] J. M. Drinkwater, R. Tsao, R. Liu, C. Defelice, and D. J. Wolyn, Effects of cooking on rutin and glutathione concentrations and antioxidant activity of green asparagus (Asparagus officinalis) spears, J. Funct. Foods, 2015, pp. 342–353. [6] G. T. Atlas and U. S. Census, World Asparagus Situation & Outlook Key Fresh Asparagus Exporters Key Fresh Asparagus Importers, 2005, pp. 1–5. [7] T. Sun, J. Tang, and J. R. Powers, Antioxidant activity and quality of asparagus affected by microwave-circulated water combination and conventional sterilization, Food Chem., 2007, pp. 813–819. [8] B. L. Benson, Update of the World’S Asparagus Production Areas, Spear Utilization and Production Periods, Acta Hortic., 2012, pp. 87– 100. [9] D. J. Makus, Mineral nutrient composition of green and white asparagus spears, HortScience, 1994, pp. 1468–1469. [10] G. A. King, K. G. Henderson, E. M. O’Donoghue, W. Martin, and R. E. Lill, Flavour and metabolic changes in asparagus during storage, Sci. Hortic. (Amsterdam)., 1988, pp. 183–190. [11] H. Zheng and H. Lu, Effect of microwave pretreatment on the kinetics of ascorbic acid degradation and peroxidase inactivation in different parts of green asparagus (Asparagus officinalis L.) during water blanching, Food Chem., 2011, pp. 1087–1093. [12] M. Blanching, E. On, and O. F. F. Asparagus, Color , Chemical and Sensory characteristics, 1996, pp.471–481. [13] E. M. Gonçalves, J. Pinheiro, M. Abreu, T. R. S. Brandão, and C. L. M. Silva, Carrot (Daucus carota L.) peroxidase inactivation, phenolic content and physical changes kinetics due to blanching, J. Food Eng., 2010, pp. 574–581. [14] J. Y. Song, G. H. An, and C. J. Kim, Color, texture, nutrient contents, and sensory values of vegetable soybeans as affected by blanching, Food Chem., 2003, pp. 69–74 [15] U. Kidmose and H. J. Martens, Changes in texture, microstructure and nutritional quality of carrot slices during blanching and freezing, J. Sci. Food Agric., 1999, pp. 1747–1753. [16] N. Muftugil, Effect of Different Types of Blanching on the Color and the Ascorbic Acid and Chlorophyll Contents of Green Beans, J. Food Process. Preserv., 1986, pp. 69–76. [17] I. Sotome et al., Blanching of potato with superheated steam and hot water spray, LWT - Food Sci. Technol., 2009, pp. 1035–1040. [18] L. Neri, I. H. Hernando, I. Pérez-Munuera, G. Sacchetti, and P. Pittia, Effect of Blanching in Water and Sugar Solutions on Texture and Microstructure of Sliced Carrots, J. Food Sci., 2011, pp. 23–30. [19] P. Brat et al., Daily polyphenol intake in France from fruit and vegetables., J. Nutr., 2006, pp. 2368–2373. [20] P. H. S. Santos and M. A. Silva, Retention of vitamin C in drying processes of fruits and vegetables - A review, Dry. Technol., 2008, pp. 1421–1437. [21] E. Cieślik, A. Grȩda, and W. Adamus, Contents of polyphenols in fruit and vegetables, Food Chem., 2006, pp. 135–142. [22] M. F. Kozempel et al., Application of Leaching Model to Describe Potato Nutrient Losses in Hot Water Blanching, J. Food Sci., 1982, pp. 1519–1523. [23] M. A. Shams and D. R. Thompson, Quantitative Determination as Affected by Conventional of Pea Losses Water Blanching, 1987, pp. 4–7. [24] S. M. Castro et al., Effect of thermal blanching and of high pressure treatments on sweet green and red bell pepper fruits (Capsicum annuum L.), Food Chem., 2008, pp. 1436–1449. [25] S. Gupta et al., Effect of different blanching treatments on ascorbic acid retention in green leafy vegetables, Nat. Prod. Radiance, 2008, pp. 111–116. [26] G. Oboh, Effect of blanching on the antioxidant properties of some tropical green leafy vegetables, LWT - Food Sci. Technol., 2005, pp. 513–517. [27] V. Dewanto, X. Wu, K. K. Adom, and R. H. Liu, Thermal Processing Enhances the Nutritional Value of Tomatoes by Increasing Total Antioxidant Activity Thermal Processing Enhances the Nutritional Value of Tomatoes by Increasing Total Antioxidant Activity, J. Agric. Food Chem., 2002, pp. 3010–3014. [28] T. E. Puwastien, P., Siong, G. Kantasubrata, J., Craven, and K. Feliciano, R. R., Judprasong, Manual of Food Analysis, Asean, 2011, pp. 188.
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[29] Y.S. Velioglu, G. Mazza, L. Gao, and B.D. Oomah, Antioxidant activity and total phenolics in selected fruits, vegetables, and grain product, J. Agric. Food Chem., 1998, pp. 4113–4117. [30] A. Braca, N. De Tommasi, L. Di Bari, C. Pizza, M. Politi, and I. Morelli, Antioxidant principles from Bauhinia tarapotensis, J. Nat. Prod., 2001, pp. 892–895. [31] W. Li, M. Zhang, and H. Q. Yu, Study on hypobaric storage of green asparagus, J. Food Eng., 2006, pp. 225–230. [32] R. Bridges, James W. A., Dietary fiber content of selected foods, Am. J. Clin. Nutr. 2018, pp. 440–447. [33] A. K. Jaiswal, S. Gupta, and N. Abu-Ghannam, Kinetic evaluation of colour, texture, polyphenols and antioxidant capacity of Irish York cabbage after blanching treatment, Food Chem., 2012, pp. 63–72. [34] A. Andersson, V. Gekas, I. Lind, F. Oliveira, and R. Öste, Effect of Preheating on Potato Texture, Crit. Rev. Food Sci. Nutr., 1994, pp. 229– 251. [35] N. Abu-ghannam and H. Crowley, The effect of low temperature blanching on the texture of whole processed new potatoes, 2006, pp. 335– 344. [36] N. Koca, F. Karadeniz, and H. S. Burdurlu, Effect of pH on chlorophyll degradation and colour loss in blanched green peas, Food Chem., 2001, pp. 609–615. [37] S. J. Padayatty et al., Vitamin C as an Antioxidant: Evaluation of Its Role in Disease Prevention, J. Am. Coll. Nutr., 2003, pp. 18–35. [38] D. F. Olivera et al., Effect of blanching on the quality of Brussels sprouts ( Brassica oleracea L . gemmifera DC ) after frozen storage, 2008, pp. 148–155. [39] S. . Achinewhu, Ascorbic acid content of some Nigerian local fruits and vegetables, Qual. Plant. Plant. Foods. Hum. Nutr, 1983, pp. 261– 266. [40] D. Sources and N. Significance, Polyphenols : Chemistry , Dietary Sources , Metabolism, and Nutritional Significance, 1998, pp. 317-333. [41] X. Cheng, M. Zhang, and B. Adhikari, Ultrasonics Sonochemistry The inactivation kinetics of polyphenol oxidase in mushroom ( Agaricus bisporus ) during thermal and thermosonic treatments, Ultrason. - Sonochemistry, 2013, pp. 674–679. [42] M. E. Latorre, P. R. Bonelli, A. M. Rojas, and L. N. Gerschenson, Microwave inactivation of red beet (Beta vulgaris L. var. conditiva) peroxidase and polyphenoloxidase and the effect of radiation on vegetable tissue quality, J. Food Eng., 2012, pp. 676–684. [43] C. Queiroz, M. L. Mendes Lopes, E. Fialho, and V. L. Valente-Mesquita, Polyphenol oxidase: Characteristics and mechanisms of browning control, Food Rev. Int., 2008, pp. 361–375. [44] C. Y. Lee and N. L. Smith, Blanching effect on polyphenol oxidase activity in table beets materials & methods results & discussion, 1979, pp. 82–84. [45] S. Ma, J. L. Silva, J. Hearnsberger, and J. Garner, Prevention of Enzymatic Darkening in Frozen Sweet Potatoes by Water Blanching : Relationship among Darkening , Phenols , and Polyphenol Oxidase Activity, 1992, pp. 864–867. [46] A. Jaiswal and N. Abu-Ghannam, Blanching as a Treatment Process: Effect on Polyphenols and Antioxidant Capacity of Cabbage, Process. impact Act. components food, 2015, pp. 35–43. [47] J. A. Larrauri, C. Sánchez-Moreno, and F. Saura-Calixto, Effect of Temperature on the Free Radical Scavenging Capacity of Extracts from Red and White Grape Pomace Peels, J. Agric. Food Chem., 1998, pp. 2694–2697. [48] E. Z. Liu and M. G. Scanlon, Modeling the effect of blanching conditions on the texture of potato strips, 2007, pp. 292–297. [49] I. Amin and Y. L. Wee, Effect of different blanching times on antioxidant properties in selected cruciferous vegetables, J. Sci. Food Agric., 2005, pp. 2314–2320.
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ICMPC-2019
Water blanching conditions on the quality of green asparagus butt segment (Asparagus officinalis L.) Thi Van Linh Nguyen1,2*, Tan Thanh Vo3,4, Tri Duc Lam3,4, Long Giang Bach3,4 2
1 Faculty of Chemical Engineering and Food Technology , Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam. Centre of Excellence for Authenticity, Risk Assessment and Technology of Food, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam 3 NTT Hi-Tech Institute, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam 4 Center of Excellence for Biochemistry and Natural Products, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam
Abstract The butt segment of asparagus contains numerous nutrients, including various antioxidants. In particular, fibers and several mineral contents are quite high. However, asparagus butt segment quality is reduced in processing. Therefore, research on the asparagus butt segment processing for development of food industry and for the benefit of economic is necessary. Water blanching is a pretreatment method applied in most fruit and vegetable industry today. Water blanching process can inhibit enzyme activity and reduce loss of food quality. However, water blanching can lead to loss of nutrient contents as well as changes in color and texture (sensory values). In this study, the temperature was investigated at 700C, 750C, 800C, 850C, and 900C, and the blanching time was observed at 2, 4, 6, and 8 minutes. We evaluated the effect of blanching conditions through the percent retention of vitamin C, phenolic compounds, antioxidant capacity (DPPH assay), and changes of sensory values. The results show that blanching temperatures from 750C to 850C insignificantly affect quality of asparagus butt segment. However, nutrient contents and sensory values decrease rapidly with the increase of blanching time. When asparagus was blanched at 850C for 4 minutes, the percent retention of vitamin C, phenolic and antioxidant capacity was 74.84% 80.34% and 71.24%, respectively. These results suggested the good blanching conditions for asparagus butt segment processing. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: Asparagus butt segment; Water blanching; Free-radical scavenging ability; Sensory values
1. Introduction Asparagus (Asparagus officinalis L) is classified in Liliaceae family. This plant is rich in nutrients. It is a very good source of protein, vitamins such as vitamin A, vitamin B1, vitamin C, vitamin E, and minerals such as Mg, Ca, P, Fe [1]. Asparagus contains many antioxidant compounds, for example rutin, ascorbic acid, tocopherol, ferulic acid. Rutin is the highest antioxidant compound in asparagus [2]. * Corresponding author. E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
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Moreover, asparagus also contains protodioscin, a substance which is classified in saponin groups that can against cancer cell and decrease cholesterol level in blood [3]. Asparagus is classified as one of the highest antioxidant containing vegetables and the fourth highest total phenolic content in twenty three vegetables which are consumed regularly in America [4]. The benefit of asparagus to human health is very high as asparagus can reduce the damage of brain and heart’s pathology, prevent inflammation of the colon and intestine’s diseases, reduce bleeding, and fortify the capillary walls [5]. Fresh asparagus is consumed in many countries. China, America, Peru, and Mexico are the top four countries consuming asparagus in the world, average over 50.000 tons each year [6]. However, asparagus can be deteriorated easily after being harvested. Consequently, several methods are applied to preserve asparagus such as drying, freezing, and canning. These process will limit a loss after harvesting asparagus, increase economic value because of long trade time [7]. When using green asparagus spears, consumers and producers only use the bud (or tip) and the middle section of the spear for processing and often discard the butt segment (or bottom of the spear) [8] because the butt segment contains insoluble fiber which makes it difficult to use. However, the results of scientific publication show that asparagus butt segments have remarkable nutritional value. Specifically, butt segment contains higher concentration of minerals such as Al and Fe than buds and middle sections [9]. Butt segment has high fiber content, and loss of nutrient contents during storage is low [10]. With suitable technology processing, it is possible to utilize this source of material to create products providing fibers and bioactive ingredients for customers and at the same time create value of the materials which used to be discarded, in food processing. Blanching is a pretreatment method which is applied in most vegetable and fruits processing industry. Nowadays, there are three following blanching methods: hot water blanching, steam blanching, and microwave blanching. Water blanching is the most popular method in manufacturing because it is the simplest and the most economical method. [11]. Normally, the temperature of water blanching generally fluctuates between 700C and 1000C [12]. The main purpose of blanching is to inhibit enzyme activities such as polyphenol oxidase, peroxidase, lipoxygenase, and phenolase [13]. However, the blanching process can change the color, texture, and content of nutrients in materials [14], [15]. A number of studies related to blanching process have been conducted. Muftugil (1986) investigated the effect of different methods on green bean and found that when being water blanched, green bean can remain color better than with other blanching methods [16]. Sotome et al. (2009) found that superheated steam and hot water spray methods can better decrease a loss in color and texture than water blanching on potatoes [17]. Neri et al. (2011) investigated the effect of water blanching and sugar solutions (maltose and trehalose) on the texture of sliced carrots and noticed that the effect of sugar solutions was insignificant in 900C [18]. Vegetable and fruits contain important compounds such as vitamin C and polyphenols. These compounds can prevent cancers and heart diseases [19]. Vitamin C is an essential compound which human can’t synthesis [20]. It is destroyed by pH, temperature, light, oxygen, enzyme, and metal catalyst, so vitamin C content is considered a food quality assessment standard [20]. Polyphenols are a group of natural compounds including flavonoids, tocopherols, coumarins. Polyphenol compounds can better prevent oxidation than antioxidant vitamins [21]. That is the reason why the investigation of the effect of parameters on the quality process of vegetable and fruits such as soybeans [14], potatoes [22], peas [23], sweet green and red pepper fruits [24], and green leafy vegetables [25] needs to evaluate the loss of nutrient contents (vitamin C, polyphenols, etc.). Although nutrient contents are important to a quality product, antioxidant activity is also a worth-caring indicator. Therefore, Ganiyu (2005) when studying the effect of blanching process on quality of green vegetables, has measured both vitamin C, polyphenol, and antioxidant activity. The results proved that vitamin C and antioxidant activity were lost in the blanching process but total polyphenol content increased [26]. However, Dewanto et al. (2002) showed that vitamin C content decreased but antioxidant activity increased during thermal treatment of tomatoes in 880C [27]. Nowadays, research information about water blanching on asparagus is still limited, especially for asparagus butt segments. Particularly, the information about the effect of water blanching process on the quality of asparagus butt segments isn’t available until now. From the problem mentioned above, the aim of this study was to investigate the effect of water blanching process on the quality of green asparagus butt segments. Temperature and time’s water blanching will be investigated and evaluated based on the percentage of retention of ascorbic acid, total polyphenol, and antioxidant capacity as well as the sensory values (color and texture) compared to a fresh sample. From that, we can determine suitable parameters for quality asparagus butt segment processing.
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2. Material and methods 2.1. Chemicals and Reagents Green asparagus spears (Asparagus officinalis) were bought at An Phu Dong market, district 12, Ho Chi Minh City, Viet Nam. Characteristic of these selected asparagus spears were green, and they were not damaged. The green asparagus spears were washed. The butt segments were cut into 5 cm lengths. The asparagus butt segments used in this study were 5.0 ± 0.5 cm cylinder and 0.5 ± 0.2 cm diameter (Fig. 1.).
Fig. 1. Green asparagus material used in the study (before and after cutting)
2.2. Chemicals Folin-Ciocalteu Reagent (FCR), Gallic acid, DPPH (2,2-diphenyl-1-picrylhydrazyl), and Trolox (6-hydroxy2,5,7,8-tetramethylchroman-2-carboxylic acid) were bought at Sigma-Aldrich Chemie, Co Ltd (USA), and 2,6dichlorophenolindophenol (DCPIP) was imported from India. Other chemicals such as distilled water (with pH between 6.5 and 8), metaphosphoric, methanol (99.5% purity), Na2CO3 (99.5% purity), ascorbic acid (99.7% purity) were originated from China. 2.3. Water Blanching Process This study, water blanching was investigated with two important factors of the process which were temperature and time. Experiments were designed by the one-factor-at-a-time method. Five levels of blanching temperature investigated were 70, 75, 80, 85, and 900C, and four levels of experimental blanching time were 2, 4, 6, and 8 minutes. After being blanched, the sample was cooled rapidly in cold water with temperature about 5.00C 0.50C. Then, sample was analyzed to determinate the retention of vitamin C and phenolic compounds as well as the antioxidant capacity (free-radical scavenging ability). 2.4. Analytical method Determination of ascorbic acid Ascorbic acid content in material and in the sample after being blanched will be determined according to AOAC 967.21 based on oxidation of ascorbic acid with 2,6–dichlorophenolindophenol (DCPIP) to dehydroascorbic acid
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and the colorless lenco derivatives [28]. Optimized reaction is at pH between 3 and 4. In this environment, a drop of excess blue DCPIP will make solution turn pink. A 5-gram of the sample was ground and extracted with metaphosphoric acid. A 5 ml of extract was titrated with 2, 6-dichlorophenolindophenol (DCPIP). The titration stopped when a drop of excess blue DCPIP makes solution turn pink in acidic medium and last for 15 seconds. Indophenol solution was titrated with the standard ascorbic acid solution. The ascorbic acid content was expressed in mg per gram of dry matter (mg/g dry matter). Determination of total phenolic content The total phenolic content was measured by the Folin-Ciocalteu colorimetric methods, using gallic acid as a standard and being described previously by Velioglu et al. (1998) [29]. The sample (5-gram) was ground and extracted with distilled water at the ratio of 10:1. The extract was placed at room temperature about 30 minutes and then filtered through Whatman No.1. The residue was extracted twice in the same way. The extracts were taken to the norm and analyzed. Extracts (1 ml) were put in a dark tube and added 1ml Folin- Ciocalteu reagent (diluted 10 times with distilled water) and 1 ml sodium carbonate solution (20% w/v). The sample was placed in dark space before being taken to a photometer at an absorption of 765 nm. The total phenolic content was expressed in mg of gallic acid equivalent per gram of dry matter (mg GAE/g dry matter). Determination of antioxidant capacity by DPPH Antioxidant capacity was measured by scavenging free radical (DPPH) which was performed based on the method described by Braca et al. (2001) [30]. Antioxidant compounds had the ability to scavenge free radicals so it discolor purple in DPPH solution. The sample (5-gram) was ground and extracted with methanol. The diluted extract (0.2 ml) was mixed with 3 ml DPPH solution. The sample was kept in the dark about 30 minutes and then measuring absorbance at 515 nm. The result was expressed by mg of Trolox equivalent per gram of dry matter (mg TE/g dry matter). Sensory evaluation After sample was blanched at different mode, its color and texture will be evaluated compared to a fresh sample. Sensory evaluation was performed by description methods of Li et al. (2006) [31]. The results were expressed by image and sensory description. Analysis of data All experiments were conducted in triplicate. The mean and standard deviation of the results were calculated using Microsoft Excel program (Microsoft Inc., Redmond, WA, USA). Experiment data was analyzed using oneway analysis of variance (ANOVA) test in SPSS program (IBM Company, USA) with the level of significance at 5%. 3. Results and discusstion 3.1. Investigating asparagus material Vitamin C content, total phenolic content, and antioxidant capacity (DPPH) of asparagus in the study were determined. These results were analyzed based on specific segments of an asparagus spear as shown in Table 1. These results showed that nutrient content of butt segment is quite high with 78% of Vitamin C content, 50% of total phenolic content, and 50% of antioxidant capacity of bud segment. Moreover, butt segments also have many other nutrients and minerals which offer essential nourishment to intensify and protect human health [9]. Therefore, removing butt segments in processing to make industrial products causes a big loss of the value of asparagus butt segments. Furthermore, asparagus butt segments provide fiber content (32 g/100g dries) [32]. Fibers has an important role to the human body because fiber can treat and prevent some diseases such as heart disease, obesity, diabetes, intestinal disorders Therefore, butt segment asparagus had many potentials to make products that bring health benefit, for example vegetable powder, nutrient powder, or herbal tea. Table 1. Parameters effect on the essential oil yield Bud segment
Butt segment
Vitamin C content (mg)
1.845 0.150
1.433 0.118
Total phenolic content (mg GAE)
8.423 1.159
4.338 0.430
12.560 0.450
6.564 0.274
Antioxidant capacity (DPPH) (mg TE)
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3.2. Investigating the effect of temperature in water blanching process Effect of blanching temperature on sensory values of asparagus butt segment Table 2 showed color and descriptive texture of asparagus butt segment was blanched at different temperatures. Color and texture are two important factors to evaluate the possibility of consumer acceptance of products. Regarding texture, table 2 showed the changes of the hardness due to blanching temperature changing from 700C to 900C. The higher the temperature is, the softer the texture of asparagus is. The difference in texture was not clear at temperatures of 700C and 800C. During the blanching process, pectin hydrolysis reaction, as well as pectin dissolution, would affect the cell wall and middle lamella leading to change hardness vegetable tend to soften [33]. Anderson et al. (1994) also showed the higher the temperature, the more destroyable the texture and the hardness of the plant cell wall [34]. Abu-ghannam and Crowley (2006) also reported the destruction of texture to happen strongly at temperature of 800C [35]. Table 2. Color and texture of asparagus butt segment in water blanching process at different temperatures Fresh
700C
750C
800C
850C
900C
Texture
Hard
Slightly soft
Slightly soft
Slightly soft
Soft
Very soft
Color
Green
Darker green
Darker green
Darker green
Olive green
Olive yellow green
Image
As for color, the above table also showed the color changes due to blanching temperature changes. From 700C to 80 C, the green color of asparagus become darker than the fresh sample. At temperature below 800C, the polyphenol oxidase activity may not be inhibited. Therefore, polyphenol content in plant cells was converted into o-quinones making asparagus become darker. Begum and Brewer (1996) reported that when asparagus was blanched, the green of asparagus becomes greener than fresh sample, but at the same time, it also becomes yellower [12]. Asparagus segments had yellow green color markedly at 850C and 900C because of the destruction of chlorophyll and free coloring compounds when they were diffused into hot water [33]. Chlorophyll is the main pigment creating the green color of vegetable and is a characteristic indicator of a quality green vegetable. Chlorophyll is destroyed easily by enzyme, pH, oxygen, light, and temperature. Therefore, the destruction of chlorophyll takes place during water blanching process and other processing [36]. Effect of blanching temperature on nutrient compounds (vitamin C and total phenols) Figure 2 showed the retention of ascorbic acid and total polyphenol at different temperatures. When temperature increased, ascorbic acid content tended to decrease and got lowest value at 900C (37.31 % 1.342). However, no significant difference of the percent retention of vitamin C from 700C to 850C with ANOVA test at a level of significance of 0.05. Vitamin C is the essential nutrient for human health. This chemical composition is considered an antioxidant found in most vegetable and fruits. Vitamin C can prevent some cancer diseases [37]. Vitamin C was destroyed because of oxidation reaction under the catalysis, which depends on many factors such as temperature, concentration of oxygen, light, water activity, and catalysts [26]. During the blanching process, the deterioration of vitamin C occurs primarily by temperature and exposure to water. However, there was no significant difference in vitamin C retention at different temperatures between 700C and 850C due to the structural characteristics of the material. Asparagus has a hard structure. At a temperature of 850C, the rate of decomposition of vitamin C was faster, but the structure of asparagus under heat condition, which is softened, leads to more extraction of vitamin C in grinding process compared to harder sample. Zheng and Lu (2011) showed the structure of the materials would 0
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affect the loss of ascorbic acid [11]. Moreover, Olivera also explained the plant tissues were destroyed by high temperature, affecting the extraction of substances from plants [38]. The loss of vitamin C content in vegetable and fruits via blanching process ranging from 32% to 68% was reported by Anchinewhu (1983) [39]. At 900C, Vitamin C content decreased dramatically because the structure of asparagus cells was destroyed leading to increased diffusion of vitamin C into blanching solution. Moreover, the temperature which is too high also accelerates the decomposition of vitamin C.
100 90
Retention (%)
80
a
a
a a
70
a
a a b
60
b
50 b
40 30 20 10 0
Vitamin C Total Phenolic
70 83.59 76.19
75 79.59 76.50
80 80.23 60.95
85 75.92 76.19
90 37.31 59.34
Fig. 2. Green asparagus material used in the study (before and after cutting)
Changes in the percentage of total phenolic retention were also shown in figure 2. Polyphenol retention tended to decrease from 70 to 800C, then increase at 850C, and again decline at 900C. There was no significant difference in the percent retention of polyphenols content at 700C, 750C, and 800C. The loss of phenolic content could be mainly due to the effect of temperature. The higher the temperature was, the more the decomposition was [13]. However, polyphenol content was higher at 850C maybe relate to inhibition of polyphenol oxidase. The decomposition of polyphenol occurs following two mechanisms which are catalysis of enzyme and auto-oxidant. Enzyme polyphenol oxidase (PPO) is responsible for the major mechanism which is the oxidation of polyphenol [40]. PPO is an enzyme which presents in most plant tissues. It is capable of catalyzing the oxidation reaction of monophenolic compounds into o-diphenols and o-dihydroxy into o-quinones [41]. PPO enzyme activity decreases the nutritional and sensory values of fruit and vegetable products [42]. Oxidation of phenolic compounds by PPO is considered to be the main cause of the brown color of many fruits and vegetables [43]. Therefore, inhibition of PPO enzyme is a necessity for the food industry today. There were many studies of temperature effects on PPO enzyme activity [44][41][45]. The inactive temperature of PPO enzyme in vegetable ranges from 700C to 900C [43]. This result showed that depending on the type of vegetables, the ability to inactivate enzyme was varied. Moreover, the higher the temperature is, the faster the inactivation rate is. The polyphenol content decreased sharply at 900C due to the influence of high temperature making polyphenol compounds destroyed.
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Fig. 3. The graph shows the percentage of retaining antioxidant capacity at different blanching temperatures
Effect of blanching temperatureon antioxidant capacity Figure 3 represented the changes in antioxidant capacity during a period of blanching at different temperatures. Antioxidant capacity tended to decrease and reached lowest value at 900C (49.12 % 3.445). There was no significant difference in antioxidant capacity at different temperatures from 700C to 850C. In this research, evaluation of antioxidant capacity was based on free-radical scavenging ability. The antioxidant capacity decreased when the temperature increased due to the decomposition of antioxidant compounds such as vitamin C, total polyphenol, and phytochemicals. The retention of vitamin C and total polyphenol content was lowest at 900C leading to the lowest antioxidant capacity. Jaiswal and Abu-Ghannam (2015) reported that temperature affected insignificantly antioxidant capacity in the blanching process of cabbage [46]. Larrauri et al. (1998) showed that the reduction of free radical scavenging ability increased when temperature increased in the sample processing [47]. 3.3. Investigating the effect of water blanching time Effect of blanching time on sensory values of asparagus butt segment Table 3 showed the changes of color and texture of asparagus butt segment in different periods of time. About texture, the results of table 3 noticed that when time was varied from 2 minutes to 8 minutes, the hardness of asparagus decreased constantly. At 6 minutes and 8 minutes blanching, asparagus released viscous liquid on the skin. The reason is due to the structure of green asparagus which is destroyed strongly at high temperate in a long time. The longer the exposure is, the more destructive the structure of the material gets. Liu and Scanlon (2007) reported that low blanching temperature (below 75 0C) make time had little effect on the structure of materials. However, when blanching at high temperature (over 75 0C), time together with temperature make blanched materials soften [48].
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Table 3. Color and texture of asparagus butt segment at different blanching time periods Fresh
2 minutes
4 minutes
6 minutes
8 minutes
Texture
Hard
Slightly hard
Soft
Soft, less tough, little viscous
Soft, tough, more viscous
Color
Green
darker green
olive green
olive yellow green
yellow green
Image
As for color, the result of table 3 also showed when time was changed from 2 minutes to 8 minutes, the green color of asparagus became more yellow. The green discoloration was due to decomposition of chlorophyll compounds and pigments when exposed to water for a long time. In low temperature, the time insignificantly affects to decomposition of chlorophyll. However, at high temperature, the longer the time is, the more decomposition chlorophyll content gets. This result is similar to Jaiswal et al. (2012). In other words, long blanching time will lead to a decrease of chlorophyll content [33]. Effect of blanching time on nutrient compounds (vitamin C and total phenols)
Fig. 4. The graph shows the percentage of remaining vitamin C and total phenolic content at different blanching time periods
Figure 4 showed the changes in vitamin C and total phenolic content during a period of blanching at different periods of time. Vitamin C content decreased gradually following the increase of time and reached the lowest value at 8-minute period (35.71% ± 6.606). There was no significant difference in vitamin C content between 2 minutes and 4 minutes. Vitamin C is not heat-stable and it is water-soluble, so vitamin C is strongly oxidized by exposure to temperature and water environment for a long time. This finding is similar to the report of Gupta et al. (2008) about the process of water blanching on some tropical leaf vegetables when blanching time increased gradually, the content of vitamin C decreased [25]. The changes in total phenolic were also shown in Figure 4. The percent retention of total phenolic tended to decrease and became lowest at 8 minutes (64.45% ± 0.803). There was no significant difference in total phenolic
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content between 2 minutes and 4 minutes using one-way ANOVA test (p > 0.05). The retention of total polyphenol was high at 2 minutes and 4 minutes due to exposure to temperature and water environment in a short time and the inhibition of polyphenol oxidase enzyme. However, at 6 minutes and 8 minutes blanching, polyphenol content decreased dramatically because the compounds which are contained in asparagus cells strongly released in hot water, and phenolic compounds (instance as flavonoids) were destroyed, which leaded to the changes in color and texture. This result is similar to the report of Amin and Wee (2005) where the total polyphenol content decreased following an increase in blanching time in some type of vegetables such as red cabbage, white cabbage, and mustard cabbage [49]. Effect of blanching time on antioxidant capacity
The percent retention of antioxidant capacity (%)
100
80
74.80a
71.24a
60 44.93b 35.25c
40
20
0 2
4
6
8
Time (min) Fig. 5. The graph shows the percentage of retaining antioxidant capacity at different blanching time periods
Figure 5 represented the changes in antioxidant capacity at different blanching time periods. The longer the blanching time is, the worse the antioxidant capacity gets, and it became lowest at 8 minutes (35.25% ± 3.909). There have been many studies reporting the relationship between the total phenolic content and antioxidant capacity. Velioglu et al. (1998) have proved an interaction between polyphenol content and antioxidant ability in several fruits, cereal, and vegetable [29]. In this case, Vitamin C’s and polyphenols’ decomposition leaded to antioxidant capacity decrease in asparagus. This result is similar to Amin and Wee (2005). In other words, long blanching time will lead to antioxidant decline [49]. 4. Conclusion Water blanching process of green asparagus was investigated for the effect of two important factors include temperature and time. This result showed the temperature from 750C-850C insignificantly affected the quality of green asparagus. However, when blanching from 2 minutes to 8 minutes, blanching process affected strongly on the nutrient contents as well as sensory values of butt segment asparagus. The increase of blanching time made the
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quality of product decrease. When asparagus was blanched at 850C for 4 minutes, polyphenol oxidase may be inhibited, which retained a lot of nutrient content as well as antioxidant capacity. The result of this research will support the processing of products from butt segment asparagus such as green asparagus powder, herbal tea, or nectar from asparagus. Acknowledgements This research was funded by the Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam. References [1] J. S. Negi, P. Singh, G. P. Joshi, M. S. Rawat, V. K. Bisht, Chemical constituents of Asparagus, Pharmacogn Rev., 2010 pp. 215–220. [2] N. Shokuhin, K. Gakkaishi, Evaluation of Antioxidant Determination Activity of Vegetable Extracts and of Some Active Compounds., 1994, pp. 611-618. [3] C. K. Chin and S. A. Garrison, Functional elements from asparagus for human health, Acta Hortic., 2008, pp. 219–225. [4] J. A. Vinson, X. Su, L. Zubik, and P. Bose, Phenol Antioxidant Quantity and Quality in Foods:Fruits, J. Agric. Food Chem., 2001, pp. 5315– 5321. [5] J. M. Drinkwater, R. Tsao, R. Liu, C. Defelice, and D. J. Wolyn, Effects of cooking on rutin and glutathione concentrations and antioxidant activity of green asparagus (Asparagus officinalis) spears, J. Funct. Foods, 2015, pp. 342–353. [6] G. T. Atlas and U. S. Census, World Asparagus Situation & Outlook Key Fresh Asparagus Exporters Key Fresh Asparagus Importers, 2005, pp. 1–5. [7] T. Sun, J. Tang, and J. R. Powers, Antioxidant activity and quality of asparagus affected by microwave-circulated water combination and conventional sterilization, Food Chem., 2007, pp. 813–819. [8] B. L. Benson, Update of the World’S Asparagus Production Areas, Spear Utilization and Production Periods, Acta Hortic., 2012, pp. 87– 100. [9] D. J. Makus, Mineral nutrient composition of green and white asparagus spears, HortScience, 1994, pp. 1468–1469. [10] G. A. King, K. G. Henderson, E. M. O’Donoghue, W. Martin, and R. E. Lill, Flavour and metabolic changes in asparagus during storage, Sci. Hortic. (Amsterdam)., 1988, pp. 183–190. [11] H. Zheng and H. Lu, Effect of microwave pretreatment on the kinetics of ascorbic acid degradation and peroxidase inactivation in different parts of green asparagus (Asparagus officinalis L.) during water blanching, Food Chem., 2011, pp. 1087–1093. [12] M. Blanching, E. On, and O. F. F. Asparagus, Color , Chemical and Sensory characteristics, 1996, pp.471–481. [13] E. M. Gonçalves, J. Pinheiro, M. Abreu, T. R. S. Brandão, and C. L. M. Silva, Carrot (Daucus carota L.) peroxidase inactivation, phenolic content and physical changes kinetics due to blanching, J. Food Eng., 2010, pp. 574–581. [14] J. Y. Song, G. H. An, and C. J. Kim, Color, texture, nutrient contents, and sensory values of vegetable soybeans as affected by blanching, Food Chem., 2003, pp. 69–74 [15] U. Kidmose and H. J. Martens, Changes in texture, microstructure and nutritional quality of carrot slices during blanching and freezing, J. Sci. Food Agric., 1999, pp. 1747–1753. [16] N. Muftugil, Effect of Different Types of Blanching on the Color and the Ascorbic Acid and Chlorophyll Contents of Green Beans, J. Food Process. Preserv., 1986, pp. 69–76. [17] I. Sotome et al., Blanching of potato with superheated steam and hot water spray, LWT - Food Sci. Technol., 2009, pp. 1035–1040. [18] L. Neri, I. H. Hernando, I. Pérez-Munuera, G. Sacchetti, and P. Pittia, Effect of Blanching in Water and Sugar Solutions on Texture and Microstructure of Sliced Carrots, J. Food Sci., 2011, pp. 23–30. [19] P. Brat et al., Daily polyphenol intake in France from fruit and vegetables., J. Nutr., 2006, pp. 2368–2373. [20] P. H. S. Santos and M. A. Silva, Retention of vitamin C in drying processes of fruits and vegetables - A review, Dry. Technol., 2008, pp. 1421–1437. [21] E. Cieślik, A. Grȩda, and W. Adamus, Contents of polyphenols in fruit and vegetables, Food Chem., 2006, pp. 135–142. [22] M. F. Kozempel et al., Application of Leaching Model to Describe Potato Nutrient Losses in Hot Water Blanching, J. Food Sci., 1982, pp. 1519–1523. [23] M. A. Shams and D. R. Thompson, Quantitative Determination as Affected by Conventional of Pea Losses Water Blanching, 1987, pp. 4–7. [24] S. M. Castro et al., Effect of thermal blanching and of high pressure treatments on sweet green and red bell pepper fruits (Capsicum annuum L.), Food Chem., 2008, pp. 1436–1449. [25] S. Gupta et al., Effect of different blanching treatments on ascorbic acid retention in green leafy vegetables, Nat. Prod. Radiance, 2008, pp. 111–116. [26] G. Oboh, Effect of blanching on the antioxidant properties of some tropical green leafy vegetables, LWT - Food Sci. Technol., 2005, pp. 513–517. [27] V. Dewanto, X. Wu, K. K. Adom, and R. H. Liu, Thermal Processing Enhances the Nutritional Value of Tomatoes by Increasing Total Antioxidant Activity Thermal Processing Enhances the Nutritional Value of Tomatoes by Increasing Total Antioxidant Activity, J. Agric. Food Chem., 2002, pp. 3010–3014. [28] T. E. Puwastien, P., Siong, G. Kantasubrata, J., Craven, and K. Feliciano, R. R., Judprasong, Manual of Food Analysis, Asean, 2011, pp. 188.
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[29] Y.S. Velioglu, G. Mazza, L. Gao, and B.D. Oomah, Antioxidant activity and total phenolics in selected fruits, vegetables, and grain product, J. Agric. Food Chem., 1998, pp. 4113–4117. [30] A. Braca, N. De Tommasi, L. Di Bari, C. Pizza, M. Politi, and I. Morelli, Antioxidant principles from Bauhinia tarapotensis, J. Nat. Prod., 2001, pp. 892–895. [31] W. Li, M. Zhang, and H. Q. Yu, Study on hypobaric storage of green asparagus, J. Food Eng., 2006, pp. 225–230. [32] R. Bridges, James W. A., Dietary fiber content of selected foods, Am. J. Clin. Nutr. 2018, pp. 440–447. [33] A. K. Jaiswal, S. Gupta, and N. Abu-Ghannam, Kinetic evaluation of colour, texture, polyphenols and antioxidant capacity of Irish York cabbage after blanching treatment, Food Chem., 2012, pp. 63–72. [34] A. Andersson, V. Gekas, I. Lind, F. Oliveira, and R. Öste, Effect of Preheating on Potato Texture, Crit. Rev. Food Sci. Nutr., 1994, pp. 229– 251. [35] N. Abu-ghannam and H. Crowley, The effect of low temperature blanching on the texture of whole processed new potatoes, 2006, pp. 335– 344. [36] N. Koca, F. Karadeniz, and H. S. Burdurlu, Effect of pH on chlorophyll degradation and colour loss in blanched green peas, Food Chem., 2001, pp. 609–615. [37] S. J. Padayatty et al., Vitamin C as an Antioxidant: Evaluation of Its Role in Disease Prevention, J. Am. Coll. Nutr., 2003, pp. 18–35. [38] D. F. Olivera et al., Effect of blanching on the quality of Brussels sprouts ( Brassica oleracea L . gemmifera DC ) after frozen storage, 2008, pp. 148–155. [39] S. . Achinewhu, Ascorbic acid content of some Nigerian local fruits and vegetables, Qual. Plant. Plant. Foods. Hum. Nutr, 1983, pp. 261– 266. [40] D. Sources and N. Significance, Polyphenols : Chemistry , Dietary Sources , Metabolism, and Nutritional Significance, 1998, pp. 317-333. [41] X. Cheng, M. Zhang, and B. Adhikari, Ultrasonics Sonochemistry The inactivation kinetics of polyphenol oxidase in mushroom ( Agaricus bisporus ) during thermal and thermosonic treatments, Ultrason. - Sonochemistry, 2013, pp. 674–679. [42] M. E. Latorre, P. R. Bonelli, A. M. Rojas, and L. N. Gerschenson, Microwave inactivation of red beet (Beta vulgaris L. var. conditiva) peroxidase and polyphenoloxidase and the effect of radiation on vegetable tissue quality, J. Food Eng., 2012, pp. 676–684. [43] C. Queiroz, M. L. Mendes Lopes, E. Fialho, and V. L. Valente-Mesquita, Polyphenol oxidase: Characteristics and mechanisms of browning control, Food Rev. Int., 2008, pp. 361–375. [44] C. Y. Lee and N. L. Smith, Blanching effect on polyphenol oxidase activity in table beets materials & methods results & discussion, 1979, pp. 82–84. [45] S. Ma, J. L. Silva, J. Hearnsberger, and J. Garner, Prevention of Enzymatic Darkening in Frozen Sweet Potatoes by Water Blanching : Relationship among Darkening , Phenols , and Polyphenol Oxidase Activity, 1992, pp. 864–867. [46] A. Jaiswal and N. Abu-Ghannam, Blanching as a Treatment Process: Effect on Polyphenols and Antioxidant Capacity of Cabbage, Process. impact Act. components food, 2015, pp. 35–43. [47] J. A. Larrauri, C. Sánchez-Moreno, and F. Saura-Calixto, Effect of Temperature on the Free Radical Scavenging Capacity of Extracts from Red and White Grape Pomace Peels, J. Agric. Food Chem., 1998, pp. 2694–2697. [48] E. Z. Liu and M. G. Scanlon, Modeling the effect of blanching conditions on the texture of potato strips, 2007, pp. 292–297. [49] I. Amin and Y. L. Wee, Effect of different blanching times on antioxidant properties in selected cruciferous vegetables, J. Sci. Food Agric., 2005, pp. 2314–2320.