Effects of Preheating on Properties of Aggregates and of Cold-Set Gels of Whey Protein Isolate

Various concentrations (1-9%) of whey protein (WP) isolate solutions were heat-denatured at 80 °C for 30 min. Size exclusion HPLC and dynamic light scattering revealed formation of soluble aggregates in 3-9% denatured WP solution. Size and content of the aggregates increased with increases in preheated WP concentration. The 4-9% denatured WP solutions were diluted to 3% WP with distilled water. Upon addition of CaCl₂ (20 mM) or glucono-δ-lactone (0.6%, w/v), all 3% denatured WP solutions formed gels at 37 °C. Hardness of the gels (3% WP) remarkably increased with WP concentration during preheating or with the aggregate size and content. The HPLC elution profiles showed that prolonging the heating (80 °C) time (2-30 min) for 8% WP solution also gradually increases aggregate size and concentration, which then led to increases in hardness of cold-set gels. The results may guide companies in how to manipulate aggregate size and content during developing WP products with capacity for cold gelation.