Measurements and Analyses of Changes in Thermo-physical Properties and Process of Heat Transfer for Foods during Cooking

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An attempt was made to analyze quantitatively the kinetics of heat transfers of foods in cooking procedure using model systems so as to simplify the constitutional and operational complexities occurring during food preparations. The details of this study can be summarized, as follows :1. It was tried to prepare a series of food models for heating in view of the moisture content, which may play a significant role in the heat transfer of foods. The newly prepared models were one of the concentrated disperse systems consisting of an equivalent mixture of wheat flour and cocoa powder suspended in the optional mixtures of water and corn oil, while the moisture in the models was able to vary from ca.7 to 50 wt % without any failure of molded shape during heating. The measurements were made to clarify the correlation between the thermal diffusivity and moisture of the models.2. An assembly of the heating device for modeling a variety of cooking was provided in order to detect the heat flux al … More ong by the one-dimensional axis in food materials from the beat transfer media. The heating device provided could follow the increasing temperature with reasonable reproducibility at the different locations of 0 mm, 1 mm, 3 mm and 5 mm along by the one-dimensional axis in the foods from the heating media during the procedure such as pan heating, steaming, boiling, flying, or baking.3. It was found out that the increasing temperature at the different inside-locations of the models and some practical foods during the various types of heating could be generalized by an exponential function, which was derived from the retardation phenomenon of thermal flux.4. The time constant corresponding to the retardation time of the newly derived equation depends on the distance from the heating medium for each sample to be tested, while the value for the time constant obtained experimentally is deeply concerned with the thermal diffusivity of each sample at an inside-location. This result suggests that if the above correlation can be confirmed with more practical cases using this exponential function, it will be sure to estimate changes in the inside temperature of food materials during cooking. Less