Conditions Under Which Bacterial Amylases Survive Ultrahigh Temperature Sterilization

The α-amylase of the thermophile Bacillus stearothermophilus 1518 was used as a model enzyme to examine the heat resistance of a bacterial amylase at ultrahigh temperature in a starch-based pudding. When heated in the laboratory pudding at 143°C for the equivalent of 22.2 set, approximately 26% of the initial amylolytic activity was retained. The presence or absence of individual ingredient groups (starch, caseinate-nonfat dry milk, oilemulsifiers, salts, or sucrose) of the pudding had no significant effect on amylase heat resistance. A combination of any two of the starch, caseinate-nonfat dry milk, or oil-emulsifier ingredients were found to be important for thermostability. The amylase of the mesophile Xanthomonas campestris 13957–2 exhibited similar thermal inactivation characteristics.