Development of continuous flow microwave and hot water bath system for destruction of spoilage microorganisms in food
2017
DUHAN, SANDEEP | KAR, ABHIJIT | NAIN, LATA | PATEL, AVINASH SINGH | DASH, SANJAYA K
A continuous pasteurization system was designed based on a domestic microwave oven. Broth was pumped through helical coils of glass tubing placed in the center of the oven cavity. Inactivation of two selected spoilage microorganisms, Bacillus cereus and Saccharomyces cerevisiae in broth were evaluated under continuous flow microwave heating conditions and compared with conventional batch heating in a well stirred hot water bath. Inoculated broth was heated in a microwave oven (700 W, 2450 MHz) under continuous flow conditions to selected exit temperatures of 90°C for B. cereus and 60°C for S. cerevisiae at five power levels (210, 280, 350, 420, 490 W) and five time intervals (1, 2, 3, 4, 5 minute). Broth treated in hot water bath at 90˚C for B. cereus and 60˚C for S. cerevisiae was taken as control. There was a decrease in B. cereus and S. cerevisiae count after microwave and hot water bath treatment (control) with increasing treatment time. Higher microbial inactivation was observed at lower power levels. For all the microwave power levels, higher inactivation of B. cereus and S. cerevisiae was observed in comparison to control, this may be due to some non thermal effects associated with microwave. Heating rate and flow rate also increased with the increasing power level with decrease residence time to kill the contaminants. In future, this system may be useful for effective pasteurization of liquid foods e.g. sugarcane juice and soymilk without affecting the taste of processed juices.
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