On how kappa-casein affects the interactions between the heat-induced whey protein/kappa-casein complexes and the casein micelles during the acid gelation of skim milk

Morand, M.; Guyomarc'h, F.; Pezennec, S.; Famelart, M.-H.

International Dairy Journal 21(9): 670-678


ISSN/ISBN: 0958-6946
DOI: 10.1016/j.idairyj.2011.01.012
Accession: 070653105

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Heat treatment of milk at 85-95 degrees C has long been reported to increase the pH of gelation and firmness of acid milk gels; hence its wide application in yoghurt manufacture. These changes have been attributed to the formation of heat-induced whey protein/kappa-casein complexes in the milk, to which heat-denatured whey protein ingredients may be substituted. However, variations in resulting gels show that a possible role of kappa-casein in determining the functional acid-gelation property of the complexes needs investigating. Model heat-induced whey protein/kappa-casein complexes were produced of kappa-casein content from 0 to 40% (w/w), but of similar size, secondary structure, surface hydrophobicity and thiol/disulphide distribution. These complexes were added to whey protein-free skim milk systems and the resulting acid-gelation behaviour of the milks was evaluated. The results showed a modification of the pH of gelation that was explained more by variation of the pI of complexes than by the kappa-casein content.