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Antioxidant and antihyperglycemic potential of soybean hydrolysates

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Title: Antioxidant and antihyperglycemic potential of soybean hydrolysates
Author(s): Darmawan, Rudy
Advisor(s): de Mejia, Elvira G.
Department / Program: Food Science & Human Nutrition
Discipline: Food Science & Human Nutrition
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: M.S.
Genre: Thesis
Subject(s): Alcalase hydrolysis β-conglycinin Cultivar Growing location Oxygen radical absorbance capacity (ORAC) Soy peptide Protein Pepsin pancreatin hydrolysis α-glucosidase inhibition Type 2 diabetes
Abstract: Protein hydrolysates are considered as a potential dietary source of natural antioxidants with important antihyperglycemic activity. This study was conducted to understand the effect of conventional and low-glycinin soy cultivars on the protein profiles and antioxidant capacity (AC) of their alcalase hydrolysates. The cultivars were grown in three different locations to identify which cultivar(s) exhibited the highest AC across multiple growing regions after alcalase hydrolysis. The peroxyl radical scavenging AC of soy peptides were also compared against purified β-conglycinin and glycinin hydrolysates. Another part of the study was conducted to understand the effect of in vitro simulated digestion of protein-based beverages and ingredients on the production of peptides with potent AC as well as α-glucosidase and α-amylase inhibitory activities. Nine protein-based beverages and ten functional ingredients (I-5 to 14) were analyzed for their AC and starch-hydrolyzing enzymes inhibitory activity. Four beverages and four protein-based ingredients were selected for in vitro digestion using pepsin and pancreatin. Statistical differences were observed in the protein profiles and AC among the different cultivars tested (p<0.05). Cultivars 1 and 6 had lower β-conglycinin subunits in comparison to the other cultivars. The hydrolysates from cultivar 3 grown in Bloomington, IL exhibited the highest AC against peroxyl radicals, compared to the other cultivars. Growing location appeared to have no effect on the soybean protein profiles and AC of soy protein hydrolysates. On average, AC for low glycinin soybean, high glycinin soybean and purified BC hydrolysates were not significantly different (p>0.05). Purified GL hydrolysate had an AC of 28.5 µM TE/µg soluble protein which was significantly different than low glycinin soybean hydrolysates (p<0.05). All beverages showed no inhibition of α-amylase activity and only commercial 1, regular soymilk and low-glycinin soymilk beverages inhibited α-glucosidase by 9.8, 9.4 and 10.2%, respectively. Non-protein based ingredients 8 and 14 exhibited α-glucosidase inhibitory activity with IC50 of 16.7 and 88.5 µg/mL, respectively and α-amylase inhibitory activity with IC50 of >2,500.0 and 325.1 µg/mL, respectively. After pepsin-pancreatin hydrolysis, the AC and α-glucosidase inhibitory activity of protein-based beverages and ingredients increased significantly (p<0.05). Upon hydrolysis, SAI 3 hydrolysate (SAI 3H) and SAI 4 hydrolysate (SAI 4H) had higher α-glucosidase inhibitory activity with 84.5 and 85.5%, respectively, than 1.0 mM acarbose with 62.8% inhibition. SAI 3H and 4H had similar peptide mass profile and were composed of unique peptides with masses 649.19, 884.55, 1108.60, 1139.73, 1152.43 and 1267.91 m/z. The study demonstrated the effect of cultivar, but not of growing location, on the soy protein subunit composition and AC of alcalase hydrolysates. The study also suggested the possibility to modify the protein profiles of soybean through breeding programs to produce soy hydrolysates with high AC, which could be further utilized as functional food ingredients. Another part of the study highlighted the importance of in vitro simulated digestion of protein-based beverages and ingredients on the production of peptides with potent antioxidant as well as α-glucosidase and α-amylase inhibitory activities. Overall, this research emphasized the importance of enzymatic hydrolysis to improve the antioxidant and antihyperglycemic potential of protein-based products.
Issue Date: 2010-05-18
URI: http://hdl.handle.net/2142/16002
Rights Information: © 2010 by Rudy Darmawan. All rights reserved.
Date Available in IDEALS: 2010-05-18
2012-05-19
Date Deposited: May 2010
 

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