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Authors: Sandeep Kumar
Advisor: Anil Dahuja
Title: Biochemical and Molecular Studies for Elucidation of the Role of Isoflavones in the Improvement of Flavour Quality of Soybean
Publisher: Division of Biochemistry ICAR-Indian Agricultural Research Institute New Delhi
Language: en_US
Type: Thesis
Agrotags: null
Keywords: Biochemical and Molecular Studies for Elucidation of the Role of Isoflavones in the Improvement of Flavour Quality of Soybean
Abstract: Soybean (Glycine max (L.) Merr) is a nutrient rich crop but has limited consumer acceptability due to the presence of off-flavour leading to its limited use in various food products. Small aldehydes and ketones are mainly responsible for this offflavour. These compounds are produced via sequential action of lipoxygenase (LOX) and hydroperoxide lyase on PUFAs abundantly present in soybean. Increasing the inherent antioxidant potential of soybean seeds is currently being envisaged as a promising strategy to control off-flavour. Isoflavones are one of the various antioxidants present in soybean considered responsible for its health benefits. Isoflavone come under the class of polyphenolic compounds and are of different chemical forms. In soybean genistein, daidzein and their glycosidic forms are the major isoflavones present. In addition to these small amounts of glycitein and its derivatives are also present. Due to the inhibitory effect of the isoflavone on lipoxygenase activity and inherent antioxidant potential; an increased content of isoflavones can help in controlling off-flavour. In the present study, the isoflavone content and composition in seed samples of 17 soybean genotypes was determined with a total isoflavone content ranging from 155.53µg/g for PUSA 40 to 1151.26µg/g for Bragg. Further, to find the correlation between isoflavone profile and lipid peroxidation, TBA number and carbonyl value, known indices of off-flavour were calculated in these genotypes. The results showed a significant negative correlation of these parameters with genistein: daidzein ratio. Two contrasting genotypes of soybean viz. Bragg (high isoflavone) and PUSA 40 (low isoflavone) were selected on the basis of total isoflavone content and gene expression analysis was done for the two isoforms of isoflavone synthase (IFS1 and IFS2) which is a key enzyme involved in isoflavone biosynthesis, at various stages of seed development. Expression studies revealed a higher expression of IFS2 in Bragg as compared to PUSA 40 towards later stages of seed development. Besides, expression of IFS2 showed positive correlation with total isoflavone content at all the stages examined. Furthermore, the level of IFS2 expression increased 8.6 fold at 55 DAF w.r.t. the level at 35 DAF in Bragg but a continuous decrease in its expression was observed in PUSA 40 from 35 DAF to 55 DAF. Also, a 1566bp cDNA sequence encoding IFS2 was cloned, characterized and submitted to NCBI (GenBank Acc. No. KT581120.1). In-silico characterization of IFS2 revealed 521 amino acid long protein with a 10 amino acid long cytochrome P450 cysteine heme-iron ligand signature sequence. The information generated from this study can further be used for the development of ‘High-isoflavone’ soybeans with improved nutritional and flavour characteristics.
Description: t-9407
Subject: Biochemistry
Theme: Biochemical and Molecular Studies for Elucidation of the Role of Isoflavones in the Improvement of Flavour Quality of Soybean
These Type: M.Sc
Issue Date: 2016
Appears in Collections:Theses

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