The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed September 24, 2009). Thesis advisor: Dr. Andrew D. Clarke. Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 73-81). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 73-81). Also available on the Internet.

This study was conducted to determine the effect of heating methods (conventional and microwave), heating temperatures, and refrigerated storage on the flavor deterioration in precooked chicken parts. Chicken breasts and legs were evaluated by chemical analyses and sensory evaluation. Data was analyzed by Fisher's least significant difference (LSD) and Duncan's test. Results of the thiobarbituric acid test (TBA) indicated that heating temperature, regardless of heating method had a significant influence on oxidative deterioration. When the legs were heated for a longer time at a lower temperature, the TBA values significantly increased indicating heightened warmed-over flavor (WOF). Two-day refrigerated storage had no measurable influence on the TBA numbers. The legs generally had a higher degree of lipid oxidation reflected by higher TBA values. Heating method and 2-day refrigerated storage did not have a significant effect on the nonheme iron content of breasts or legs. The effects of heating temperature were inconsistent for the legs and breasts which was attributed to the different initial iron content of the legs, and the release of nonheme iron during the initial processing of the legs. The nonheme iron values of the legs were greater relative to the breasts. Heating and storage in general increased the area of peak 3 in legs, but had no effect on the breasts. A significant increase in the hexanal (peak 8) content of legs occurred upon 2-day storage, but not for breasts. Peak 7 significantly decreased when the breasts were heated, stored, and reheated. This was not the case for the legs. Sensory panelists could not differentiate between heating methods or temperatures for either part. / Master of Science

Ready-to-eat poultry products, which are precooked so that they can be reheated and served, have gained widespread consumer acceptance. The production of these products generally includes a process that is sufficient to destroy nonsporeforming bacterial pathogens. However, recontamination of these products after the heat process is unavoidable at some level. It could occur during processing steps where the precooked products are handled or exposed to air or unclean work surfaces, during packaging operations, or during handling by the consumer. Reheating instructions are often targeted toward maintaining the integrity of the packaging material of the product instead of the destruction of microorganisms. The objective of this study was to determine if the reheating instructions for precooked poultry products were adequate to destroy vegetative cells of potential bacterial pathogens. Listeria monocytogenes was used as the test microorganism in this study since it is one of the most heat resistant nonsporeforming pathogens that might contaminate these products. D-values were determined in selected poultry products and thermal death time curves were developed. Various ready-to-eat poultry products were obtained from manufacturing plants and from local grocery stores. The minimum and maximum recommended cook times for both microwave and conventional ovens were evaluated in triplicate for all the products. A Campbell Scientific Inc. 21X Micrologger and type T thermocouples and a Luxtron 755 Multichannel Fluoroptic Thermometer and MSA probes were used to record the subcutaneous and internal temperatures of the products heated in the conventional and microwave oven respectively. Heating curves were constructed from the raw data and F values were calculated using z-value data from the IDT curve. Inoculated pack studies were conducted with L. monocytogenes to confirm calculated data. The reheating instructions of many of the products were inadequate to destroy bacterial pathogens. The surface temperatures were usually sufficient to destroy contamination whereas the internal temperatures usually did not reach adequate levels. Since bacterial contamination generally moves from the exterior of a product toward the interior, it would seem that the inadequate interior temperatures would not be a cause of too much concern. However, during the inoculated pack studies, it appears that surface evaporative cooling allowed for survival of the L. monocytogenes. In summary, the adequacy of the heating process varied within brands, between products, and by packaging materials used. / M.S.