Glycation of caseinate by fructose and fructo‐oligosaccharides during controlled heat treatment in the ‘dry’ state

This paper investigates the controlled heating of caseinate with reducing sugars to produce glycoproteins with improved functionality for use in food. Caseinate was combined with inulin, fructose and a mixture of both inulin and fructose and the lyophilisates heated at a controlled water activity for up to 48 h. Caseinate–glucose and caseinate–lactose glycoconjugates were prepared for comparison. Conjugation between caseinate and fructose occurred readily at 60 °C and 67% relative humidity, modifying up to 75% of the lysine groups of caseinate within 48 h. Moreover, when reconstituted, the caseinate–fructose glycoconjugates showed a dramatic increase in viscosity relative to caseinate ‘dry’‐heated alone. At 80% relative humidity the reaction proceeded so rapidly that gels containing darkly coloured particulate matter were formed. Incorporation of inulin prevented formation of caseinate–fructose gels, and minimised browning development while still producing moderately viscous solutions. Based on ¹³C‐NMR, SDS‐PAGE and electron microscopy techniques, mechanisms by which inulin modified the reaction have been proposed. Copyright © 2005 Society of Chemical Industry