Inactivation of Enzymes in Namazake Using Micro-bubble Supercritical Carbon Dioxide

Glucoamylase, acid protease, and acid carboxypeptidase in namazake were inactivated with microbubble supercritical carbon dioxide (SC CO₂) at 25 MPa, 35°C for 30min. After the treatment, their activities decreased from 330, 20.1, and 115U/ml sake to 51.8, 1.8, and 0 U/ml sake, respectively. During the storage at 20°C for 60 days, no increase in amino acid value was observed. On the other hand, glucose concentration in the sake treated with SC CO₂ increased as well as namazake. The formation of lactic acid, acetic acid, and ethanol were depressed, and acidity was constant during storage. On the contrary, the decrease of pyruvic and malic acid after 20 days of storage could be depressed. Analysis of volatile compounds suggests that the treatment with SC CO₂ did not cause the formation of volatile compounds in contrast to heat-treatment. As a result of sensory evaluation, the sake treated with SC CO₂ at 20 MPa, 35°C for 30 min was given sensory scores near to those of namazake.