73C-1 |
Chemical markers as indicators of lethality for continuous microwave pasteurization of apple cider |
T. S. GENTRY and J. S. Roberts. Dept. of Food Science & Technology, Cornell Univ., W. North St., NYSAES, Geneva, NY 14456 With the growing demand for improved quality, manufacturers have looked at alternative processing methods. One area researchers are exploring is the pasteurization of fruit juices using microwave heating. Pasteurization is a conventional process designed for the destruction of pathogenic bacteria. This is a time -temperature dependent process. Microwaves can effectively raise the temperature of foods in a short time to inactivate microorganisms. However, the difficulty in calculating microbial destruction is obtaining an accurate temperature profile. Traditional methods for monitoring temperature, which are metal based have physical limitations in microwave systems. The thermophysical and dielectric properties of the food and the physical and chemical composition of the microorganism influence the effects of microwaves on microorganisms. The microbial inactivation kinetics for microwave processing needed to ensure product safety would be the same as conventional thermal processing. The purpose of this project was to assess the application of microwave heating towards the pasteurization of apple cider. Both thermocouples and fiber optic probes monitored input and output temperatures for a continuous flow microwave heating system. 5-hydroxymethyl furfural (HMF) was also used as a time-temperature indicator compound. Kinetic parameters were determined for the formation of HMF. HMF was quantified to determine the lethality of the process. Apple cider pasteurized with a given lethality was found to contain trace amounts of HMF. These levels were comparable to commercial apple cider. The lethality of the process was verified using the chemical kinetics for the formation of HMF. Microwave pasteurization is an alternative process that can extend the shelf life of apple cider. Although fiber optic probes can be used to monitor temperatures in microwave systems, they are expensive and delicate. Chemical markers provide an additional method to verify the lethality of thermal processes.
Session 73C, Food Engineering: Transport Processes and Kinetics
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