Effect of gelation factors on the formation and characteristics of protease-induced whey protein gel

Whey protein gel formed at 10% (w/v) whey protein concentration, 0.5% E/S, pH 7.0, 55 degrees C and 2.5 mM CaCl2 concentration had an average particle size of 23.46 mu m, hardness of 0.46, cohesiveness of 0.13 and adhesiveness of 1.40, and the gel showed semisolid, smooth and creamy texture. There were no distinct changes in gel textural properties after heating at 80 and 90 degrees C for 5 min, respectively, or being kept at 4 degrees C for 1 month. The textural properties of the gel showed no significant difference after its pH was adjusted to 4.5, 5.5 and 7.5 compared with that of pH 6.5 (control gel). However, the average particle size significantly increased after being adjusted to pH 4.5 and pH 5.5. Transmission electron micrographs showed that protease-induced gel possessed much looser aggregate structure compared with heat-induced compact gel, which may give support to its potential application in low-fat foods that no need of extensive heating.