Moisture of Foods and Food Models Playing a Role in the Thermal Conduction During Cooking

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According to the results obtained from the case studies on the heat conduction in foods during cooking, these types of works have been continued so as to obtain further insights into the role of moisture in the various heating ptocedures. The contents of the experimental studies and results obtained can be summarized, as follows :1) An assembly for detecting changes in the inside temperature of foods during heating was improved for extending location of the measuring temperature in a range from the heating plane to 10mm along by the one dimensional axis in the sample.2) A preliminary examination was made to obtain informations on the interrelation between the mechanical behaviours and the thermal properties of foods using a testing machine newly installed.3) The inside temperature of the highly moisturized gels (more than 98wt%) prepared with the various polysaccharides was observed during heating in a metal vessel. The examined increasing patterns of the inside temperature indicated t … More he type of thermal conduction in all the gels to be tested. All the patterns could also be expressed by an exponential equation reported before.4) The wheat flour doughs moisturized in a wide range (10wt%〜82.5wt%) could be prepared by mixing Na-alginate and corn oil. The heating patterns of the models were compared with each moisture in different methods of cooking such as steaming, boiling, baking, flying and heating in a metal vessel. The heating pattern obtained could be written by the exponential equation for all the cases, while the time constant of the equation correlated to the thermal diffusivity of the models for the cases of flying and heating in a metal vessel.5) The effect of phase transition of the components on the heating pattern of foods during cooking was observed by some cases, i.e. melting of fats, sol transition of agar gels, thermal gelation of egg proteins, and thermal expansion of wheat flour doughs. The increases of the inside temperature were obviously disturbed by the endothermic transition of each component. The phenomenon of the thermal expansion accelerated pronouncedly the rate of increasing temperature for wheat flour doughs in the presence of the baking powder.. Less