Methods to assess heating patterns and develop process procedure for microwave sterilization of packaged foods

摘要

Microwave heating is an effective volumetric heating method that can potentially be used in high temperature-short-time sterilization to produce high quality shelf-stable packaged foods. Commercial microwave sterilization processes are currently used in Japan and Belgium, but are not used in the US, due to stringent US Food and Drug Administration (FDA) regulations for food safety. Research has been conducted at Washington State University (WSU), in collaboration with several government and industrial partners to develop a technology that can pass FDA approval. The microwave sterilization technology developed at WSU relies on the use of 915 MHz frequency and a single mode design. Very good results have been obtained for relatively homogeneous foods such as mashed potato, fish fillets and chicken breast. But there is a need to establish reliable methods for the development of commercial thermal processes that can obtain regulatory approval. The objective of this study was to develop reliable means to locate cold spots in foods during microwave sterilization process and to monitor temperatures of those locations needed for developing thermal processing procedures. Specifically, a method was developed that relies on chemical marker formation in foods to locate the cold and hot spots in packaged foods such as mashed potato after heating in the microwave sterilization cavity with the WSU microwave-circulated water combination heating technology. Temperature history during the MW sterilization process was recorded using fiber optic sensors and data mini logger packaged inside the foods. The study shows that chemical marker, data mini logger and fiber optic sensors can be effective for the development of products and sterilization process for the microwave-circulated water combination technology.