Comparison of protein degradation as a consequence of germination time and temperature in rye and barley malts

The influence of germination time and temperature on proteins and proteolytic activity in barley and rye malts were investigated using response surface methodology as a statistical tool. Total nitrogen content was not affected by variations in germination conditions for either grain. In experimental worts, soluble nitrogen significantly (P < 0.05) increased in malts for both grains as a consequence of longer germination periods, with rye malts having considerably higher soluble nitrogen contents than barley malts. High amounts of free amino nitrogen were measured in rye malts and increased over the germination period. In barley malts, long germination periods and high germination temperatures significantly increased free amino nitrogen. In rye malts, only germination time affected proteolytic activity significantly. The molecular weight of the proteins was measured by capillary electrophoresis. Long germination periods caused significant protein breakdown in both grains. In barley, breakdown was enhanced by applying high germination temperatures.