<研究報告>炊飯過程における部位的変化について(第三報) : 二段消火式ガス炊飯器の場合

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With two purposes, the present experiments have been carried out on rice cooked by a two-step switch-off gas cooker, Rinnai 5-C, an advanced type of a Rinnai 5-A cooker. First, to see whether the same partial difference could be observed in this type of a cooker as observed in the conventional one, on the one hand, and to examine some interrelationship between the results obtained and the objective phenomena, on the other, rice at an upper periphery, a center part and the bottom of a center were subjected to the sensory tests. And measurements were also done on some factors which expected to be responsible for taste at the above-mentioned parts at the times of turning-on the flame, boiling, the first and the second turning-off the flame and at the end of cooking. The results are as follows. The tests by the scoring and the ranking method revealed that there was no significant difference in taste of rice among an upper periphery, a center part and the bottom of a center part. Objective tests: 1. Water content. At the time of the second turning-off the flame, it decreased in the order of a center part, an upper periphery and the bottom of a center. This trend persisted until the end of cooking. In the conventional type of a cooker, the water content was reversed between the bottom of a center and an upper periphery. 2. Ratio of increase in volume. At the time of the first turning-off, it decreased in the order of an upper periphery, a center part and the bottom of a center. From that time on, the differences reduced and became much smaller at the end of cooking, as compared with those in the conventional cooker. 3. "Cells" of the grain. At the time of boiling, they seemed to be sharper at the bottom of a center than at the other parts, as revealed in the cross sections. After the time of the second turning-off there was little partial difference. 4. Rates of dehydration. At no time points there was any significant partial difference. This is in a sharp contrast to the results obtained with the conventional type of a cooker. 5. Firmness, elasticity, and viscosity. All of these decreased in the order of the bottom of a center, an upper periphery and a center part at the time of turning-off. The values remained unchanged until the end of cooking. They were all much smaller as compared with those obtained with a 5-A cooker. 6. Ratio of gelatinization. Little partial difference was found at any time point. 7. Changes in temperature. No difference was detected at the three parts between the times of boiling and the second turning-off. This was the same as in 5-A. It was 100℃ at these time points but, the reafter, it was lower by 1-2℃ at an upper periphery by the end of cooking. This decrease in temperatuse was much smaller than when a 5-A cooker was used. 8. Heat transfer coefficient At the switch-off time of the main flame the temperature difference between an upper periphery and the bottom of a center part was smaller than in 5-A. The second purpose of the present experiments was to examine whether there was some difference in taste between the rice cooked by 5-A and that by 5-C. The sensory tests by paired preference tests demonstrated that the rice cooked by 5-C was more tasty than that cooked by 5-A at the 5% level of significance.
福岡女子大学の論文
1980-03-01

<研究報告>炊飯過程における部位的変化について(第三報) : 二段消火式ガス炊飯器の場合

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