Kinetics of aggregation and gelation of globular proteins after heat-induced denaturation

The rate of native protein consumption upon heating solutions of beta-lactoglobulin at pH 7 and 0.1 M salt is characterized by a single activated process for temperatures up to 85 degrees C. The activation energy is only weakly dependent on the protein concentration and is about 390 kJ/mol. The effective order of the reaction responsible for the decrease of native proteins is 1.5, independent of concentration and temperature in the range investigated (2.5-115 g/L; 52-76 degrees C). Gel times were measured over a wide range of concentrations (9-180 g/L) and temperatures (55-87 degrees C). The temperature dependence of the gel time is characterized by the same activation energy as the consumption of the native proteins. The concentration dependence of the gel time diverges when the concentration approaches 7 g/L independent of the heating temperature. The divergence occurs when all native proteins have aggregated before the gel is formed. The growth of the aggregates was measured using light scattering. Below 7 g/L the growth of the aggregates stagnates.