COMPARISON OF MICROWAVE, CONVENTIONAL AND COMBINATION HEAT-TREATMENTSON WHEAT-GERM LIPASE ACTIVITY

Commercial wheat germ lipase inactivation was analysed at various temp eratures with reference to conventional and microwave heating. A tempe rature controlled water-bath was used for conventional heating. A cust om designed microwave temperature control system was used to maintain test samples at selected temperatures either by full exposure to micro waves (microwave heating) or partial exposure by immersion in water (i n a beaker) maintained at the desired temperature using the microwave oven (mixed mode). Lipase inactivation was analysed using first-order kinetics resulting in activation energies (E(a)) Of 20.9, 25.4 and 18. 7 kcal mole-1 for the conventional, microwave and mixed mode heating, respectively. The activation energies of conventional and mixed mode h eating were somewhat more comparable, while the microwave mode resulte d in a slightly higher activation energy. The higher enzyme inactivati on rate constants observed under microwave heating conditions were att ributed to possible non-thermal effects associated with microwave ener gy.