Theses and Dissertations

Author

Yan Zhang

Issuing Body

Mississippi State University

Advisor

Chang, Sam K. C.

Committee Member

Haque, Zahur Z.

Committee Member

Nannapaneni, Ramakrishna

Committee Member

Li, Jiaxu

Date of Degree

1-1-2017

Document Type

Dissertation - Open Access

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Abstract

Lentil, black soybean and black turtle have been proved to be phenolic-rich legume varieties and possess higher antioxidant activity. In this study, the three legume varieties were subjected to broad range of processing conditions, and the effects on phenolic contents, antioxidant capacity and individual phenolic acid were investigated. The results showed all processing methods could decrease the total phenolic content, and steaming processing could preserve more phenolics and antioxidant activity than boiling processing. Phenolic acids mainly existed in nonree form and the content of individual free phenolic acids was dependent on the thermal process applied. When in vitro gastrointestinal simulation digestion was applied to the thermally processed beans, it was found that the properties of hydrolysates including total phenolic content, antioxidant activity, degree of hydrolysis, and ACE (angiotensin converting enzyme) inhibitory activity were all affected by thermal conditions employed. There was a weak correlation between the degree of hydrolysis and ACE inhibition. In the current study, for each legume variety, cooking conditions which yielded the highest phenolic content and antioxidant activity were selected. Phenolics of the raw and cooked seeds from each legume variety were extracted, semi-purified (XAD-7) and further fractionated (Sephadex LH-20). The results showed cooking had great effects on yield, phenolic content, antioxidant capacity, and individual phenolic compounds. The phenolic content and antioxidant activity could be enriched tremendously in the semi-purified extracts and some fractions. Some phenolic compounds which were absent in raw material could be found after cooking in the fractions and some phenolic compounds which were present in raw material disappeared after cooking. Among crude phenolic extracts, semi-purified extracts and fractions, only crude extracts showed ACE inhibition. In addition, protein isolates from the legumes varieties were treated with in vitro GI (gastrointestinal) digestion and then separated by ultrafiltration, DEAE anion exchange chromatography and gel permeation chromatography. After ultrafiltration, the lowest molecular weight fraction (< 3kD) had the highest ACE inhibition and the three legume varieties showed different peptide distribution, ACE inhibition, and antioxidant profile in the hydrolysates. Gel filtration chromatography further revealed that the most potent ACE inhibitors were peptides of 2-5 amino acids long.

URI

https://hdl.handle.net/11668/19349

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