The effects were studied of pH and salts on the properties of mixed gels consisting of whey protein (WPI, 6%) and gelatin (3%).
The apparent rupture stress of the WPI and alkali-treated gelatin gel increased with increasing pH value, while the rupture stress of the WPI and acid-treated gelatin gel showed peaks at pH 3.5 and 4.5. When 0.1_N calcium chloride, and 0.1 _N magnesium chloride was added to the WPI (0.6%) and alkali-treated (0.3%) gelatin mixed sol, the transparency decreased with increasing temperature and an aggregate was formed. The effect of sodium citrate on the WPI and alkali-treated gelatin sol was to form a macromolecular aggregate formed at more than 80°C, this aggregate formation being accelerated under the conditions of 90°C for 10 min. The strength of apparent rupture stress of the mixed gels depended upon which salt was added. The highest rupture stress was observed with addedcalcium chloride, which was followed in decreasing order by chloride and sodium citrate. This order was directly correlated with the percentage of bound water.