Dried shiitake mushroom (Lentinula edodes Sing.) and its stock are widely used in Japanese cooking. The flavor of the stock, prepared by soaking dried shiitake mushrooms in water, is affected by the soaking time and the temperature of the water in which the mushrooms are soaked.

The volatile components of shiitake mushroom stock prepared by three different soaking conditions were investigated using GC-Olfactometry, GC-MS, and sensory evaluation. The odor concentrates of the stock were extracted by two methods : solvent assisted flavor evaporation after solvent extraction and simultaneous distillation and extraction.

Based on aroma extract dilution analysis, our results suggest that dimethyl trisulfide, dimethyl tetrasulfide, 1,2,4,6-tetrathiepane, and other sulfur compounds contributed to the characteristic odor of the stock prepared from dried shiitake mushrooms. The odor of the stock prepared by soaking at 38°C for 30 min was preferred in the sensory evaluation.

Sweet potato shows a gradual change in flavor during baking. We studied the change of volatile composition and sensory properties of headspace aroma from baked sweet potato. Sensory evaluation indicated the aroma after 75-90 minutes from beginning of baking at 200°C was most favorable. The extract was obtained by purge and solvent trapping, and studied by GC, GC-MS and GC-olfactometry. Application of aroma extract dilution analysis (AEDA) revealed 16 odor-active components. Most of these components were generated by some thermal processes such as amino-carbonyl reaction, strecker degradation, carotenoid degradation and ferulic acid degradation. They showed the different patterns of increase according to type of generating process.

We analyzed volatile compounds of Chionoecetes japonicas by gas chromatography/mass spectrometry (GC/MS). The volatile compound from the mid-intestinal gland of Chionoecetes japonicas was clearly increased by heating.

We lowered the pH of the samples taken from the leg muscle and mid-intestinal gland of Chionoecetes japonicas by adding citric acid. Sensory evaluation was used to evaluate any alteration to the smell of the samples following the addition of citric acid. Fluctuations of volatile compounds were analyzed using GC/MS. We found a reduction in both the smell of the samples and some of the volatile compounds with the addition of citric acid and its affect on pH.　Results showed that trimethylamine was the active compound contributing to the odour of crab.

In biofiltration systems for gaseous pollutants control, appropriate range of moisture and nutritious ingredients have to be maintained in a packed bed to obtain a stable performance. In this study, mass-transfer mechanisms of ammonium chloride in the biofiltration, which treats gaseous VOCs (volatile organic compounds) and which has the packed bed of porous PVF (polyvinyl formal) irrigated by soaking, were evaluated through a simplified soaking experiment focused on nitrogen source as the key constituent. And a series of experiments on biofiltration of gaseous VOCs was carried out for the following two purposes : to specify an optimal condition of soaking-irrigation, and to compare the performance between the system with soaking-irrigation and that with trickling-irrigation which is commonly applied. Results showed that soaking-irrigation was more effective than trickling-irrigation in removal of gaseous toluene, a hydrophobic component. With regarding 75% of moisture content of packed bed as the boundary value, molecular diffusion and irrigating-water advection were dominant mass-transfer mechanisms of nutritious materials in higher and lower moisture content, respectively. However, the amount of mass-transfer of nutritious material in lower moisture content tended to be lower than that is expected by the estimation under the amount of advection with water transfer. Excess frequency of soaking-irrigation led to excess biomass growth in the packed bed, and this is possibly derived not from excess nitrogen source but from water accumulation. Soaking-irrigation had better be conducted after that moisture content of packed bed is confirmed to be below 75%.