An Approach to the Evaluation of the Physical Quality of Rice Cakes.

Abstract

It is known that the deterioration of rice cakes largely depends on the temperature of the environment after manufacture of the rice cakes. The reason for this is that the physical state of water in the rice cakes is changed by the application of heat, and the restoration properties of the rice cakes are eventually lost. This study was made to numerically express the degree of deterioration of rice cakes based on the relationship between the temperature and the conductivity of the rice cakes. Four types of rice cake samples with different degrees of deterioration were prepared by repeating a heat treatment of 60°C for one hour, using a rice cake immediately after manufacture, The conductivities of these rice cake samples were measured as they were frozen by decreasing the temperature from 0°C. Measurement of the conductivity of the rice cake samples confirmed that thetemperature at which the conductivity drops sharply, due to freezing of the water in the rice cake, is related to the degree of deterioration. The deterioration is caused by the movement of water in the rice cakes when the moisture content of the rice cakes is controlled within the range of 41.5 to 44.0% at manufacture. This temperature can be used as an index to indicate the degree of deterioration of rice cakes. This fact was supported by DSC and DTA analyses, and the data for the solubility of starch in hydrochloric acid. In addition, it has been judged from a taste test of rice cakes manufactured without using any additives that there is a quality limit to the rice cake samples which were prepared by multiple heat treatments (three times). The conductivity drop temperature of the above-mentioned sample was-6.0±0.5°C.