Temperature-composition phase diagram and gel properties of the gelatin-starch-water system

The gelatin-starch-water system has been studied at different temperatures, at a total biopolymer concentration of 5.0 wt%. The weight ratios (W) of gelatin/starch used were 9:1, 8:2..... 2:8, 1:9, with pH values between 5.82 (at W = 9:1) and 6.50 (at W = 1:9). The systems were characterized theologically and by turbidity measurements to construct a phase diagram in the temperature (T) and composition (W) variables. The T-W quadrant consists of three regions: a single-phase solutions region (A) and regions of complete and incomplete phase separation (B and C, respectively). The system in region C is a gel. Region B, lying between A and C, corresponds to two co-existing liquid phases. The transition from A to C (obtained by cooling the system at constant W) involves crossing region B. The properties of the resulting gels depend on the rate of this intersection. Gels formed on rapid cooling have an even distribution of turbidity, whereas slow cooling gives two gel layers of different turbidity. The gelation temperature and gel strength of the mixed systems are dominated by the gelatin component, with no indication of network formation by starch. Copyright (C) 1996 Elsevier Science Ltd.