Rheology, texture and microstructure of whey proteins/low methoxyl pectins mixed gels with added calcium

Gelation of a whey protein isolate mixed with various industrial low methoxyl pectins (LMPs) has been investigated. Ratios were adjusted to keep whey protein (WP) concentrations constant at 8%. Pectin and calcium concentrations were fixed at 0.1%, 0.5%, 1.0%, 1.5% and 0, 5, 10 mm, respectively. The pH was adjusted to 6.0. Heat treatment at 80degreesC was used to induce WP gelation. Heating WP solution mixed with LMP allowed gel formation with lower protein concentration than normally observed; syneresis was also reduced. The type and proportion of pectin, as well as the calcium concentration affected gel hardness. Increasing the amount of pectin and the calcium concentration made mixed gels firmer. White gels were observed indicating aggregation of WPs. The gelation of the mixed systems appeared to have occurred through a phase separation and a competition between biopolymers for the binding of water and calcium. (C) 2002 Elsevier Science Ltd. All rights reserved.