Continuous microwave heating process, evolved recently, recommends itself for foods that cannot be exposed to high temperatures for long periods. Modern technologies, evolved mostly by the dairy industry for pasteurization and sterilization of milk like HTST, have helped to market stabilized fluid milk with extended shelf life using the aseptic packaging systems. Invariably in all these thermal processes, the food has to be in contact with the heating surface for transfer of heat from the source to the food material under processing that can cause some practical problems. Microwave heating, basically a batch process has so far remained untapped with the industry looking for a continuous process with assured performance.
Development of the continuous process recently, which is patented, has opened up immense possibilities for thermal treatment of many pumpable food products. "The IMS Cylindrical Heating System features patented technology that delivers uniform heating on a continuous flow basis, minimizing the problem of hot spots in traditional thermal processing technologies," said a company statement. "Because the food product is heated in seconds and is not in contact with a hot heating surface, the unique thermal process allows for ultra-rapid pasteurization or sterilization with minimal product degradation."
While pH, sugar and salt in the product determine the process parameters, optimum temperature-time relationship for effective sterilization will also depend on the flow characteristics of the product to be processed. Foods with high acidity or salt or sugar with uniform consistency are easier to be handled, It is the low acid foods which pose challenges as the contaminating microorganisms require much more rigorous heating to achieve assured "kill" rate. The new microwave processing system is claimed to be efficient for low acid foods also which is commendable. Use of steam for thermal processing of liquids may become history if the microwave system becomes the accepted norm..