The purpose of this study was to examine the mechanism of pressure-induced gel (PG) formation of hen egg yolk. Egg yolk forms gels by high-pressure processing (over 450MPa) at temperatures above 15℃. PG (20℃, 650MPa) showed the highest "Gel Strength" and "Work Done values". Furthermore, these parameters increased with increasing protein concentration. N-ethylmaleimide was used to inhibit formation of PG and heat-induced gels (HG). Result of non-reducing SDS-PAGE showed that apo-LDL from plasma and granule fractions and apo-HDL from granule fraction were the main proteins that form PG and HG. In addition, disulfide bonds play an important role in gel formation; however, there were no significant differences between PG and HG in disulfide bond formation. The structure of PG and HG consisted of a network of fine strands and the surface structure was different between PG and HG as observed by scanning electron microscopy. PG showed a thick and smooth surface, whereas HG showed a thin and rough surface. These results suggested that PG formation of hen egg yolk occurred via disulfide bond formation. Therefore, the physicochemical characteristics of PG were much different from those of HG.

　In this study, moisture content changes in cooked rice during hot air drying, equilibrium moisture contents (EMCs) of dried cooked rice at various temperature and relative humidity conditions, and moisture content changes in dried cooked rice during water sorption were investigated and predictions were made for each course of moisture content. Results showed that the exponential model was applicable in describing the moisture content changes in cooked rice during hot air drying, and the calculated drying rate constant had Arrhenius type temperature dependency. The EMC of dried cooked rice, which is considered an important index for preservation, fitted the GAB model with high accuracy. It was also found that the moisture content changes in dried cooked rice during water sorption could be predicted by Page's equation. In addition, sensory test of cooked rice that is made from dried cooked rice (dried cooked rice was rehydrated by water sorption at 40℃ for 30min, followed by microwave heating at 500W for 1min) indicated no significant difference (p>0.05) in taste compared to that of the reference.

　The purpose of this study was to investigate the mechanism of β-lactoglobulin (β-lg) pressure-induced gel (PG) formation at low to medium temperatures (0～20℃). β-lactogrobulin formed gels by high-pressure processing (HPP) at 20℃. The protein concentration required for PG formation was 125 mg/mℓ or greater. The PG at 20℃ and 650MPa showed the greatest gel strength and work done values. PG and heat-induced gel (HG) formation was inhibited by N-ethylmaleimide. Free sulfhydryl (SH) groups of β-lg increased with increasing processing temperature. The number of free SH groups after HPP at a medium temperature (20℃, 600MPa) was significantly higher than after HPP at a low temperature (0～10℃, 600MPa). However, SH content after HPP at medium temperature was approximately half of the SH content after heat processing (90℃, 0.1MPa). Non-reducing SDS-PAGE showed that β-lg oligomers were formed by HPP. In this investigation, formation of oligomers and increased coomassie brilliant blue dye staining intensity were temperature-dependent. These results suggest that free SH groups of β-lg increased in a temperature-dependent manner. Therefore, formation of β-lg PG is caused by the formation of high molecular weight oligomers by intermolecular disulfide bonds.

　We proposed an improved method based on the ethane efflux method of C ameron and Yang for measuring the resistance to gas diffusion in plant tissues. The effect of temperature and fruit size on the resistance and the conversion from the resistance to ethane diffusion to that to gaseous O₂ and CO₂ diffusion were also investigated using citrus Iyo fruit (Citrus iyo hort. Ex Tanaka). The results were in good agreement with those of the original method, and were obtained in a shorter amount of the time. The resistance to ethane diffusion depended on both the temperature and fruit size; specifically, the higher the temperature, the lower the resistance and the larger the fruit size, the higher the resistance. Finally, we presented equations to predict the resistance to O₂ and CO₂ diffusion using values measured with the ethane efflux method.