Journal of Food Processing & Technology

Abstract

Enhancement of Non-thermal Treatment on Inactivation of Glucoamylase and Acid Protease Using CO2 Microbubbles

Pokhum C, Chawengkijwanich C and Kobayashi F

Thermal treatment is usually used for food pasteurization and enzyme inactivation. However, it has an adverse effect on the quality of thermal-sensitive food such as fruit juice, Japanese sake, milk, yogurt and jam. In this study, we presented an alternative method for a non-thermal treatment with at 45 and 50°C for glucoamylase and protease inactivation using pressurized carbon dioxide (CO₂). Twelve liters of enzyme solution (0.004% glucoamylase or 0.015% protease) was fed into a low pressure (2 MPa) CO₂ mixing vessel. CO₂ microbubbles (MB-CO₂) were generated by introducing the mixture through a swiveling microbubble generator. The mixture containing MB-CO₂ was flowed to incubate in a heating coil at various conditions (temperature at 45 or 50°C and pressure 2, 4, or 6 MPa). After incubation, the mixture was sampled at 10, 20 and 30 min from the sampling valve. The relative residual activities of glucoamylase and acid protease were measured by a spectrophotometer at the absorbance of 400 nm (Abs400) and 660 nm (Abs660), respectively. Relative residual activity of glucoamylase with MB-CO₂ treatment at 50°C and 4 MPa was 15.01% whereas 74.83% of glucoamylase activity was found from treatment without MB-CO₂ at same temperature. For acid protease, relative residual enzyme activity with MB-CO₂ treatment at 45°C and 4 MPa was 2.29% whereas that without MBCO₂ treatment at 45°C was 81.25%. These results suggested that glucoamylase and acid protease could be inactivated effectively at 45 and 50°C present of MB-CO₂.