Doctor of Philosophy (PhD)
School of Nutrition and Food Sciences
Consumers with full-time jobs prefer microwavable-frozen-meals for convenience when lack time to cook. Microwaves do not require a medium for heat transfer and provide quick heating even in low thermal conductivity foods, which does not occur in conventional heating. The main problem in utilizing microwave-heating for cooking is the non-uniform temperature distribution in foods which may result in insufficient lethality of microorganisms in some part. This non-uniformity can be due to a number of factors including composition and geometry of food. The objectives of this study were to develop a mathematical-model based on Maxwell¡¯s equations for predicting the temperature distribution in frozen oyster- meats undergoing microwave-heating and to solve the mathematical-model of the microwave heating process for frozen-oysters with finite-element-software. Oyster meats were analyzed for proximate analysis. The thermal properties of oyster were determined by Choi and Okos¡¯s equation. The dielectric properties of oyster meat were measured by transmission line method. Oyster meats were frozen cryogenically at -20¡ÆC and weight, shape, and dimensions of the frozen-meats were measured. The frozen samples were placed in a laboratory Microwave-Workstation with a maximum power of 1200 W at the operational frequency of 2450MHz. Temperature sensors with fiber optic leads were used to minimize interactions with microwaves. The sensors were connected to a computer with a FISO commander direct acquisition system. Temperature profiles were plotted in real-time during microwave heating. A model based on the Maxwell¡¯s equations was developed and used to model the heat generation during microwave-heating. The model predicted hot spots and cold spots in the oysters. Fresh oysters were heated to 100¡ÆC within 12 sec with the microwave heating. Frozen oysters reached 100¡ÆC after 20 sec of microwave-heating. The temperatures of oysters immediately after microwave-cooking ranged from 85.9 to 100.3¡ÆC, which evidenced that microwave cooking creates non-uniform-heating. The root-mean-square-error of the predicted-temperature vs. actual experimental values at hot spots ranged from 0.23 to 5.47 ¢ªC. This is decent agreement, and thus provides confidence in the model¡¯s ability to predict temperature-profiles of frozen-oyster-meats during microwave-cooking. The models were also employed to predict the temperature distribution for oyster meat-contained microwavable instant meals.
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Zhang, Jie, "Mathematical and Computer-Based Models for Optimizing Microwave Heating Processes of Frozen Oysters" (2013). LSU Doctoral Dissertations. 1966.