Studies on Microbial Destruction by Continuous Microwave Heating System through Helical Coils

Abstract

Three specially designed glass helical coil applicators were introduced to study the effects of microwave heating on microorganisms and following process parameters were evaluated: input power (1200?1800 W) and Flow rate (100-1000ml/min), and inlet temperature (30?C). Water at neutral pH was used to study the heating characteristics. The 2kW microwave heating system consisted of cubical cavity with glass helical coil applicator of different diameters A, B and C separately, which was shown to produce uniform exit temperature throughout the experiment .Process lethality was verified based on inoculation of Aspergillus niger spores in water. From the transit-time and temperature measurements, time-temperature profiles were generated and kinetic data of microbial destruction were evaluated as a function of system variables. Destruction rate is directly proportional to power and temperature. It was found that when velocity increases destruction rate decreases. Energy absorption rate increased with respect to decrease in surface area, tube diameter and with lesser velocity. Tube diameter was the dominant factor affecting heating rate as compared with flow rate and Dean Number.