13-8 |
Optimization of microwave energy for the processing of apple cider |
T. S. GENTRY and J. S. Roberts. Food Science and Technology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456 In fruit juice processing, high temperature short time processes (HTST) are important to minimize temperature gradients and maximize quality. A properly designed microwave-heating unit has the potential to be an effective HTST thermal process producing high quality food products. The microbial inactivation kinetics are similar to conventional thermal processes. Research in our laboratory has also shown microwave energy can be used to heat apple mash prior to juice extraction in order to increase phytochemicals in the juice and juice yields. This multi-functional utilization of microwave heating would make microwaves a cost-effective alternative. The purpose of this project was to assess the application of microwave energy towards the processing of apple cider. Both thermocouples and fiber optic probes monitored temperatures for a continuous microwave pasteurization system. Kinetic parameters for the formation of 5-hydroxymethyl furfural (HMF) were correlated to the total lethality of the process. In addition, studies were conducted to optimize the extraction of phenolics by heating the mash prior to pressing. Finally, total phenolics, color, and polyphenol oxidase activity were monitored over a six-week storage stability study. The lethality was verified using the chemical kinetics for the formation of HMF. Apple cider pasteurized with a given lethality was found to contain trace amounts of HMF. These levels were comparable to commercial apple cider. Sensory tests also indicated no off-flavors were produced when compared to microthermic pasteurization. Furthermore, apple mash heated to 70°C at 1800 W did show an increase in total phenolics. Microwave energy is an alternative process that can improve quality and extend the shelf life of apple cider. Furthermore, chemical markers provide an additional method to verify the lethality of thermal processes. With the optimization of both pasteurization and phenolic extraction at 1800 W, simultaneous heating of the apple mash and the cider would be an efficient process.
Session 13, Food Engineering: Thermal processes
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