Textural properties of cold-set gels induced from heat-denatured whey protein isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl₂ (10-40 nM), NaCl (50-400 mM) or glucono-delta-lactone (GDL, 0.4-2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl₂ concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.