Influence of xanthan gum on physical characteristics of heat-denatured whey protein solutions and gels

The influence of xanthan on the phase separation, optical properties and rheology of aqueous solutions and gels containing native (N) or heat-denatured (HD) whey protein isolate (WPI) was studied. In the absence of added salt, xanthan promoted phase separation in HD-WPI solutions but not in N-WPI solutions, which was attributed to the increased effective molecular weight of the heated proteins. In the presence of salt, xanthan caused a significant increase in gelation rate, shear modulus and opacity of HD-WPI solutions gelled by adding 200 mM NaCl. Rheology and turbidity measurements suggested that HD-WPI gels containing xanthan formed water-in-water emulsions consisting of xanthan-rich regions surrounded by a protein-rich aqueous phase. These results indicate that the thermodynamic incompatibility of xanthan and heat denatured whey proteins can be utilized to create products that exhibit a variety of different physicochemical characteristics. (C) 2000 Elsevier Science Ltd. All rights reserved.