Binding of volatile flavor compounds to purified soy proteins in an aqueous model system

Abstract

<p>A headspace technique was used to examine the binding of a series of volatile carbonyl compounds to highly pure soybean glycinin and B-conglycinin. Small amounts of polar lipid (<0.23%) were bound to the protein even after extensive purification. Sodium azide (0.02%) was found to greatly increase the binding constant for hexanal to glycinin. Increasing ionic strength caused changes in the number of binding sites for glycinin and number of sites and binding constant for B-conglycinin. The addition of 2-mercaptoethanol to create mildly reducing conditions did not affect the binding parameters. The number of binding sites and affinty of the carbonyls studied were greater for glycinin than B-conglycinin at 20° and 30°C. Thermodynamic parameters indicated that the binding reactions were entropy driven for the series of homologous aldehydes and ketones studied. Hexane was found to bind at 5C but not at 20° or 30°C. The 1,8-acrylaminopthalenesulfonate binding suggested that protein unfolding occurred 5°C. There were small changes in the Orange G reactive lysine after hexanal binding to the proteins. Binding of the flavor compounds may cause conformational changes which increase the binding of further molecules.</p>