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Evaluation of a sulphydryl-disulphide exchange index (SEI) for whey proteins - beta-lactoglobulin and bovine serum albumin

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Owusu-Apenten, Richard, Chee, C and Hwee, OP (2003) Evaluation of a sulphydryl-disulphide exchange index (SEI) for whey proteins - beta-lactoglobulin and bovine serum albumin. Food Chemistry, 83 (4). pp. 541-545. [Journal article]

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URL: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T6R-48NBYK6-5&_user=126978&_coverDate=12%2F31%2F2003&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000010438&_version=1&_urlVersion=0&_userid=126978&md5=634837b7f41d76cf26512235

DOI: 10.1016/S0308-8146(03)00150-X

Abstract

Sulphydryl-disulphide (SH-SS) exchange underlies many protein functions in processed foods. There is a need for reliable indicators of SH-SS exchange capacity in protein ingredients. An index for SH-SS exchange (SEI) is described using beta-lactoglobulin (BLG) or bovine serum albumin (BSA). The proteins were reacted with 2-pyridine disulphide (PDS Aldrithiol-2(TM)) or Ellman's reagent (DTNB) in a buffered medium (0.05 M phosphate buffer, pH 6.9) at 25degreesC. The 2nd order rate constant for protein SH-SS exchange with PDS or DTNB (k, M-1 s(-1)) was normalized by dividing by the rate constant for glutathione (GSH) reaction with PDS or DTNB (k*, M-1 s(-1)) determined under identical conditions. The capacity or SH-SS exchange was inversely related to SEI (= -log k/k*) values of 4.11 for BLG and 1.05 for BSA, based on measurements using PDS. Studies using DTNB yield SEI equal to 4.28 for BLG and 2.20 for BSA. The SH group of BSA was 100-1052 times more reactive than the SH group of BLG. In a medium containing 1.2 M sodium chloride the difference in SH-SS exchange capacity was similar to9000 fold. Differential scanning calorimetry (DSC) results showed that the conformational stability of BLG increased much more substantially than BSA when both proteins were exposed to 0.1-1.2 M sodium chloride concentrations. (C) 2003 Elsevier Ltd. All rights reserved.

Item Type:Journal article
Keywords:STABILITY FUNCTION RELATIONS; CONFORMATIONAL STABILITY; THIOL-GROUPS; GELATION; SALTS
Faculties and Schools:Faculty of Life and Health Sciences
Faculty of Life and Health Sciences > School of Biomedical Sciences
Research Institutes and Groups:Biomedical Sciences Research Institute
Biomedical Sciences Research Institute > Northern Ireland Centre for Food and Health (NICHE)
ID Code:14696
Deposited By:Dr Richard Owusu-Apenten
Deposited On:03 Aug 2010 08:50
Last Modified:28 Jan 2014 14:46

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