THERMAL AND SUPERCRITICAL CO2 INACTIVATION KINETICS OF BROMELAIN IN PINEAPPLE JUICE
Bromelain, a proteinase present in pineapple, has many industrial uses. It is used widely to tenderize meat, chill-proof beer, and stabilize protein emulsifiers in latex paints. It has also many pharmaceutical properties.
Bromelain is believed to cause soreness and discomfort of the mouth when excessive amounts of fresh pineapple is consumed. The presence of bromelain in pineapple juice also prevents gelatinization if the juice is used as an ingredient for gelatin. Therefore, commercial pineapple juice has to be pasteurized to inactivate the enzyme and reduce the number of microorganisms. However, a complete kinetic study with confirmation is not available. Moreover, understanding bromelain kinetics can help optimize processing to minimize the flavor loss during pasteurization.
This study investigated thermal and Supercritical CO2 inactivation kinetics of fruit bromelain. Thermal inactivation kinetics parameters such as isothermal rate constants (ke) at specific temperatures, the frequency factor (A), and the energy of activation (Ea), were experimentally determined. A model for bromelain thermal inactivation was developed to predict the residual enzyme activity in response to any varying time-temperature treatment. Moreover, the effect of high pressure carbon dioxide treatment on bromelain inactivation in pineapple juice was explored.
The thermal inactivation of bromelain was studied at 55, 60, 63, 65, and 67C and was found to follow first order kinetics. The isothermal rate constants of bromelain at any specific temperature can be predicted by the Arrhenius equation. Using the kinetic parameters found, the bromelain inactivation models were developed and validated for both constant temperature and dynamic temperature histories.
The Supercritical CO2 treatment on bromelain in pineapple juice did not affect bromelain activity in our study at either 31 MPa, 55C for 2 hours, or at 34.5 MPa, 46C for 3 hours. Rather, the inactivation of bromelain was caused by heat but not by pressure or by carbon dioxide.