We estimated the optimal heating conditions for cooking food. We had previously estimated by unsteady heat conduction the heating time for a 20-mm-thick slice of beef, indicating the difference in ...results according to the heating conditions. We estimated here the heating time for 7-mm, 10-mm and 15-mm-thick beef steaks and hamburger steaks under the optimum heating conditions necessary to obtain good results. We also simultaneously estimated the necessary heating time from the thermo-physical properties of the food and by the principle of unsteady heat conduction. We then measured the heating time for these three sample thicknesses of beef and hamburger steak. The temperature ranges used for the cooking pan were 160-220℃ for the beef steak and 150-180℃ for the hamburger steak. We compared the heating time and examined the influence of the heating temperature on the surface color and hardness of the beef and hamburger steak. A pan temperature of less than 220℃ failed to brown the 15-mm-thick beef on the surface, and the temperature at the center of the beef only rose to 85℃. The distance from the pan surface to the center of the meat sample was 1/2 of the thickness of the meat before and after heating. The color of the hamburger surface changed with the pan temperature. Although we found no difference in the meat hardness, we could show the optimal pan temperature and heating time according to the desired color of the hamburger steak. With the exception of the 7-mm-thick beef steak, we could estimate the optimal heating time by applying the principle of unsteady heat conduction and using the thermo-physical properties calculated from the various components of the meat. We achieved similar results with the hamburger steak.
There are various phases in a process of decision-making, and a process of food preparation normally presents a rich variety of such phases that would offer opportunities to train students in ...developing their decision-making capabilities. This research aims to demonstrate the effectiveness of learning food preparation in terms of the subject matter. A total of 456 university students and high school students were the subjects of this study. They were classified into two types; those majoring or specializing in food preparation and those not majoring or specializing in it. Their value consciousness and decision-making ability were analyzed on the basis of the questionnaire sent and collected both prior and susequent to respective classes of food preparation. The results of the study are as follows: The research confirmed that both the university students and the high school students majoring in food preparation showed higher learning effectiveness on their value consciousness and decision-making capabilities in food life than those not majoring in food preparation. In other words, those with learning experience in food preparation faired better than those with no such experience. From the above, it is clear that the learning effect promotes the cultivation of decision-making ability in food life.
Steam convection ovens utilize two types of heating method : convection heating and steam heating. To ascertain the heating efficiency of this type of oven, the heat transfer coefficient was measured ...with and without steam. In order to determine the cooking efficiency, the temperature increase and moisture loss of a sample potato (φ50 × 20 mm) were measured. The heat transfer coefficient was significantly higher with steam than without steam until the surface temperature of the heated food had reached 100°C. Above this surface temperature, the values with steam and without steam were nearly identical. The rate of increase in the surface temperature of the potato was in proportion to the increase in air temperature and the amount of steam, but the rate of increase in the temperature at the center of the potato did not follow this proportionality. This is believed to have been due to the fact that there was moisture loss from the potato surface at an early stage of heating when the air temperature was above 130°C with steam. On the other hand, when the air temperature was under 130°C with steam, there was no such moisture loss. These results indicate that the steam ratio and air temperature can be adjusted to control the cooking time and moisture content.
The optimum frying conditions for beef were determined by heating a 20 mm × 50 mm dia. piece of beef in a pan at various temperatures (120, 160, 180, 200 and 220°C). The respective heating times that ...were necessary to make the center temperature of a samples reach 55, 70 and 85°C were measured. After heating, the weight loss, thickness, surface color and hardness were also measured. The results indicate that the hardness and thickness were directly related to the center temperature, regardless of the pan temperature. On the other hand, the pan temperature had strong influence on the surface color, and the range of time for good browning at various pan temperatures could be defined. The heating time calculated by applying the unsteady heat conduction in a semi-infinite plate and the surface browning time range were used to determine the optimum heating conditions for beef.
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