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

The rate of native protein consumption upon heating solutions of beta-lacto globulin at pH 7 and 0.1 M salt is characterized by a single activated proc ess for temperatures up to 85 degrees C. The activation energy is only weak ly dependent on the protein concentration and is about 390 kJ/mol. The effe ctive order of the reaction responsible for the decrease of native proteins is 1.5, independent of concentration and temperature in the range investig ated (2.5-115 g/L; 52-76 degrees C). Gel times were measured over a wide ra nge of concentrations (9-180 g/L) and temperatures (55-87 degrees C). The t emperature dependence of the gel time is characterized by the same activati on energy as the consumption of the native proteins. The concentration depe ndence of the gel time diverges when the concentration approaches 7 g/L ind ependent of the heating temperature. The divergence occurs when all native proteins have aggregated before the gel is formed. The growth of the aggreg ates was measured using light scattering. Below 7 g/L the growth of the agg regates stagnates.