Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Food Science

Committee Chair

Mario Ferruzzi

Committee Member 1

Maria F. San Martin-Gonzalez

Committee Member 2

Lori A. Hoagland

Abstract

Fruits and vegetables are a rich source of health promoting micronutrients and phytochemicals, and their consumption has been associated with reduction of many chronic and degenerative disease. Thermal processing techniques are used to preserve quality and extent of the shelf life of foods, although these traditional processes are associated with specific quality changes in fruits and vegetables. Compared to traditional thermal processing methods, microwave heating provides the potential to improve product quality by virtue of its energy transfer mechanism that provides rapid volumetric heating of food and can potentially enhance overall quality of processed fruit and vegetable products. Though direct comparisons between traditional and microwave heating on quality and nutritional value of commonly consumed fruits and vegetables remain limited. The objective of these studies was to compare high value applesauce and tomato puree products processed by conventional thermal (scraped surface and tubular heat exchangers) and microwave heating systems to better understand the impact of microwave processing on quality characteristics, phytochemical profile and bioaccessibility after process and following storage.

Applesauce products formulated with apple puree were pasteurized at 96°C for 60 seconds by either a tubular (TB) heat exchanger or 915mHz Industrial Microwave System (MW) were compared after process and over 52 weeks of storage for color, viscosity and polyphenol content. Generally, no significant differences in polyphenol content of applesauce were observed between the two heating systems. Applesauce processed by MW was observed to maintain more stable color characteristics over shelf life compared to TB processed product (7.4 compared to 11). However, MW processed products were found to have slightly lower apparent viscosity (71.1Pa.s/°brix) compared to TB processed products (103.3Pa.s/°brix). Similarly, tomato puree (8°brix) was generated by hot-break (85°C) and pasteurization (121°C/4sec) using MW/MW or scraped surface/tubular configuration was compared for color, viscosity, and, carotenoid content and bioaccessibility. In contrast to applesauce findings, color stability was found to be higher in SS/TB processed products samples. Further, no differences were observed in consistency and apparent viscosity at low shear rate (1/s) between the two heating systems. However, higher apparent viscosity was observed for microwave products at higher shear rates suggesting some improvement in product consistency with MW processing.

Interestingly, no significant differences were observed in lycopene content between processes, however, lycopene bioaccessibility was observed to be higher from tubular compared to microwave processed products. Combined these findings suggest product quality attributes are similar between microwave and conventionally processed tomato and apple products.

However, further research is needed to optimize microwave processing parameters to better understand if it can be leveraged to improve product quality, flavor and other parameters for high value fruits and vegetables.

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