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Design of continuous flow thermal food processes using a computer spreadsheet |
Z. B. Maroulis and G. D. SARAVACOS. Dept. of Chemical Engineering, National Technical University, Zografou campus, Athens, 15780, Greece Application of computer aided design (CAD) to the design of thermal processing of foods has been limited by the complexity of the large engineering CAD packages and the lack of sufficient physical property and kinetics data of food systems. PC spreadsheets are useful tools for simplified computer calculations in process engineering and design, and they could be utilized in the design of thermal food processes. The objective of our work was to apply an available computer spreadsheet to the design of two continuous flow thermal food processes, i.e. pasteurization and sterilization. The MS Excel spreadsheet was used to integrate and optimize the kinetics of heat transfer and thermal inactivation of microorganisms and nutrients (quality) of liquid foods in continuous flow systems. The thermal processes were specified by the product flow rate, the inlet and outlet temperatures, the residence time, the heating and cooling medium temperatures, and the kinetics of microbial (pathogenic, thermophilic) and nutrient (vitamins B, C) inactivation. Physical property, kinetic, heat transfer coefficient, and cost data were obtained from the literature. The simplified computer spreadsheet method was applied to the continuous flow thermal processing (pasteurization and sterilization) of a typical liquid food, i.e. milk, and the optimum values of the design variables (temperatures) and cost (equipment and operating) were calculated. Temperature-time curves for both thermal processes show that the integral effect of both heating and cooling compare well with the established pasteurization (HTST) and sterilization (UHT) time-temperature specifications used in thermal processing of foods. The results of our calculations demonstrate the usefulness of the computer spreadsheet method for the design of continuous flow thermal food processes. Thermal processes can be evaluated and integrated over a wider range of time-temperature, allowing better optimization of food safety, food quality, and process cost.
Session 13, Food Engineering: Thermal processes
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