Protein ternary phase diagram .1. Effect of ethanol, ammonium sulfate, and temperature on the phase behavior of type B gelatin

The effect of ethanol or (NH4)(2)SO4 addition on aqueous gelatin solution (pH 7.0) phase behavior was examined in the temperature range from 10 to 70 degrees C for protein and solute concentrations of 0-100 wt %. Ternary phase diagrams were used to effectively illustrate the relationship between the seven protein morphologies observed. Gelatin only exists as a random coil structure above 40 degrees C. As a result, in ethanol and salt systems below 30 degrees C, one-phase or two-phase gel and liquid morphologies dominated. In contrast, above 50 degrees C, one-phase sol or two-phase coacervate morphologies occupied significant portions of the two phase diagram systems. Between 30 and 50 degrees C, a wide range of morphologies was observed in both systems, as the gelatin gradually transformed to a more random structure. Differences observed between the various gelatin phase diagrams were a result of altered protein-solute, intraprotein, and interprotein interactions caused by changing temperature, ethanol, and (NH4)(2)SO4 concentrations.