No abstract

Model food systems with Maillard reaction products have been an effective tool to assess process lethality for microwave-assisted thermal sterilization. However, model food systems used for sterilization temperatures (110-130 °C) are not optimal for pasteurization temperatures 15 (70-100 °C). The purpose of this research was to develop and assess model food systems to 16 quantify process lethality and food quality for pasteurization applications, such as microwave-17 assisted pasteurization. Chemical marker M-2 (4-hydroxy-5-methyl-3(2H)-furanone) and color 18 reaction kinetics were determined for egg white, mashed potato, and gellan model foods. M-2, 19 L*, and a* value changes followed first order reaction kinetics and were significantly correlated to thermal lethality and cook value. Mashed potato was the optimal model food, in part because it had the greatest range of L* and a* reaction rates at 90 °C. Mashed potato model foods developed in this study could be used in the future to describe safety and quality reactions during pasteurization process evaluation.

No abstract

Thermal process optimization has focused on traditional sterilization, with limited research on pasteurization or microwave-assisted thermal processing. Model foods have been developed as quality evaluation tools for thermal pasteurization processes, but there are no comprehensive studies demonstrating how these model foods could be used to evaluate and compare the resulting food quality after different pasteurization processes. The aim of this study was to develop a methodology using image and quantitative analyses for quality evaluation of pre-packaged food pasteurized using a microwave-assisted pasteurization system (MAPS) and traditional hot water method. Four pasteurization processes (MAPS and hot water method at 90 and 95°C) were designed to have an equivalent accumulated thermal lethality at the cold spot of at least 90°C for 10 min to control nonproteolytic Clostridium botulinum spores. Color-based time-temperature indicators in mashed potato and green pea model foods were quantified using image analysis. Results showed that median color values were useful in assessing overall color change, and interquartile range was an indicator of burnt areas. MAPS 95°C was the best process because it had the smallest hot spot cook values and the least color change, while the 90°C hot water process was the worst. Model foods and image analysis techniques were useful pasteurization process quality evaluation tools and made it possible to visualize the potential food quality change volumetrically, throughout a food package. In the future, these tools could be combined with computer simulations to optimize the quality of pilot-scale and industrial MAPS or conventional pasteurization processes.

Development and selection of model foods is a critical part of microwave thermal process development, simulation validation, and optimization. Previously developed model foods for pasteurization process evaluation utilized Maillard reaction products as the time-temperature integrators, which resulted in similar temperature sensitivity among the models. The aim of this research was to develop additional model foods based on different time-temperature integrators, determine their dielectric properties and color change kinetics, and validate the optimal model food in hot water and microwave-assisted pasteurization processes. Color, quantified using a value, was selected as the time-temperature indicator for green pea and garlic puree model foods. Results showed 915 MHz microwaves had a greater penetration depth into the green pea model food than the garlic. a value reaction rates for the green pea model were approximately 4 times slower than in the garlic model food; slower reaction rates were preferred for the application of model food in this study, that is quality evaluation for a target process of 90 °C for 10 min at the cold spot. Pasteurization validation used the green pea model food and results showed that there were quantifiable differences between the color of the unheated control, hot water pasteurization, and microwave-assisted thermal pasteurization system. Both model foods developed in this research could be utilized for quality assessment and optimization of various thermal pasteurization processes.