Gelation of globular protein in presence of low methoxyl pectin:: effect of Na+ and/or Ca2+ ions on rheology and microstructure of the systems

The present investigation aimed at understanding how the type of cations (Na+ and/or Ca2+) influences heat-induced gelation of globular protein/LM pectin mixtures in comparison to the globular protein only. Two globular proteins (beta-lactoglobulin or bovine serum albumin) were compared. On the basis of viscoelastic and microscopic observations (CLSM), it has been shown that the two cations play a major role in gelation of the individual biopolymers and, therefore, influence strongly the properties of the mixture. These differences are related to a competition between gelation of the protein (in absence of Ca2+) or of both biopolymers (if Ca2+ is added) and phase separation processes taking place before the mixed system is entirely gelled. (C) 2004 Elsevier Ltd. All rights reserved.