Effect of reheating on sodium-induced cold gelation of whey proteins

The effect of sodium concentration [Na] on cold set whey protein isolate (WPI) gels and the effect of reheating these gels was studied. A minimum of 75mM NaCl was required to induce cold gelation in 10% WPI suspensions, pre-heated to 80 degrees C for 30 min. This is a higher level compared to the 25 mM NaCl required for a conventional heat-induced gelation. Increasing [Na] from 75 to 400mM, during cold gelation, significantly (P less than or equal to 0.05) increased gel strength and water-holding capacity while it decreased gel elasticity. These changes paralleled a reduction in gel clarity which indicated an increase in protein aggregate size. Heating the cold set gels significantly (P less than or equal to 0.05) increased gel strength by a factor of 2.5 to 8 depending on initial [Na]. Heating also increased opacity and water-holding, suggesting the potential use of a two-stage gelation process to enhance cold set gel characteristics. (C) 1997 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd.