The relation between dehydration mechanism and water activity of filefish muscle was investigated. Filefish muscle in the form of thin plate (5x10x0.4cm) was dried in a forced air dryer at 47.5 deg Centigrade. The moisture content and the water activity at which the second falling rate period started were not constant, because the drying rate of the first falling rate period was strongly dependent on the air humidity. The second falling rate period was again divided into two drying rate periods, the former and latter periods. The diffusion coefficient of water was 2.89x10 to the negative ten power m2/sec at 47.5 deg Centigrade. At this stage, the case-hardening continued until the water activity reduced to 0.7. The latter period of the second falling rate period started at the water activity of 0.45. The number of molecular layers was 4, and the diffusion coefficient of water during this stage was 4.38x10 to the 11th power m2/sec at 47.5 deg Centigrade

One dimensional unsteady heat conduction was studied on soybean curd as a water-protein-fat food system. This heterogeneous soybean curd could be treated as homogeneous material for the unsteady heat conduction by "effective" thermal diffusivity. Measurements were made with an apparatus designed and constructed by the author and also made with ice to establish the reliability, the reproducibility and the accuracy of the apparatus. The effective thermal diffusivity of soybean curd was substantially dependent on the fraction of protein and fat as well as water

In this study, water activity (aw) of various model preparations of Kamaboko was measured and ability of lowering aw of starch, glycine and sodium lactate was discussed. In addition, the aw measurements were also compared to the predicted values of aw which were derived from the equation of Raoult's law and the linear slope method by Sloan and Labuza. The effect of starch on lowering as was very low, and glycine was more effective than starch. Sodium lactate was shown to be the most effective among humectants examined. When 7.5% was added, the aw of model Kamaboko A prepared with frozen fish meat paste of moisture content 87.1% was reduced to 0.93-0.94. Generally, prediction by the equation of Raoult's law turned out to be useful for determining aw lowering effect of humectants, excepting sodium chloride and sodium lactate. The equation of regression derived from the least squares could be applied to predicting aw in the model Kamaboko

In this study, water activity (aw) of various model preparations of Kamaboko was measured and ability of lowering aw of humectants added such as sodium chloride, sugars and polyols was discussed. The effect of sodium chloride on lowering aw was highest among all of those examined. When 4% sodium chloride as humectant was added to the model Kamaboko, the aw was reduced to 0.94 or below. Among the sugars, glucose was so effective that it lowered aw to 0.96 by adding 10%, but it would cause browning reaction on the Kamaboko surface. Glycerin was the most effective among the polyols. When it was added by 10% the aw of Kamaboko was reduced to 0.95. It was more effective to decrease aw to lower moisture content of model Kamaboko.

An apparatus for continuous measurements of sorption isotherm of dried food was manufactured to shorten the time required for equilibration. The apparatus was so designed that the temperature, air velocity and relative humidity in the experimental chamber could be controlled. The use of dynamic stream of conditioned air with a velocity of 0.2 m/sec, instead of static atmosphere, allowed a faster equilibration of dried filefish muschel at 25 degrees centigrade. The mean time necessary for the equilibration of dried filefish muscle at the water activity of a given state to a higher water activity was about 45 hours. The monolayer moisture content of dried filefish muscle calculated from BET-equation was 0.092 kg water/kg dry matter at 25 degrees centigrade.