Effects of time and temperature on process and crude palm oil quality with microwave irradiation sterilization

Abstract

Microwave sterilization of oil palm fruits aims to protect palm oil quality and facilitates stripping of oil palm fruit bunches. Microwave irradiation may reduce time and temperature for sterilization process. The purposes of this study were to determine the time and temperature to inactivate 90% lipase (D-value) and process sensitivity on temperature (z-value) for microwave sterilization. Lipase inactivation as first order reaction rate was used to determine the D-value by using D-z model, while thermal death time (TDT) method was used to determine the z-value. The D-value resulted from this study ranged from 8 to 17 min, at temperature 82 and 70oC respectively, while z-value ranged between 21 to 27oC. Kinetic constant (k) for lipase inactivation process ranged from 0.136 to 0.276 min-1. Optimum time and temperature to inactivate 90% lipase in this study were 9.7 min at temperatures of 80.5oC (12 min time of exposure and power density of 854.58 W kg-1) or 12.3 min at a temperature of 80°C (16 min exposure time and power density of 718.53 W kg-1). This study concluded microwave sterilization reduced time and temperature to inactivate lipase as compared to conventional oil palm sterilization. Process performances were indicated by high efficiency of stripping (74 and 81% respectively), and quality of palm oil (levels of free fatty acid (FFA), carotene, vitamin E and fatty acid composition) met the standards of Malaysian Palm Oil Board (MPOB) for crude palm oil (CPO).