In this study, we report a comparative analysis of the changes in the aroma characteristics of sweet potato, after boiling and saccharification during sweet potato juice production, using sensory and instrumental methods. Although the raw sweet potato sample possessed a grassy-carrot aroma, the boiled saccharified sample showed a distinct heavily boiled-sweet aroma. Furthermore, 26 and 42 flavor compounds were identified in the raw sweet potato juice and boiled saccharified samples respectively, by GC-MS. Although the raw sample showed higher levels of aldehydes, the boiled saccharified sample yielded a headspace rich in terpenoids, ketones, furans and aromatic aldehydes.Here we elucidate the mechanism of flavor compound formation and discuss the association of the identified volatiles and the characteristic aroma attributes of the boiled saccharified sweet potato.

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The characteristics and endospermous amylase activity of glutinous rice were studied. For flours prepared from glutinous rice samples of different textures, differences in cooking quality and paste viscosity were observed. From the amylase zymogram of the polished rice, bands corresponding to isozymes were detected, namely 4 amylases and 3 Debranching Enzymes (DBEs), as major bands. Among samples, some differences in band pattern and intensity, were observed. Moreover, amylase activity was observed at pH 7, the pH during cooking, and α-amylase and DBE activities differed between the samples. These activities correlated to paste viscosity (p<0.05). Thus, the endospermous amylase activity of the polished glutinous rice is considered one factor in estimating the suitability for rice processing.

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Kimchi is a Korean traditional fermented vegetable food. In recent years, kimchi has become popular in Japan and the import and production thereof have increased. Kimchi's nutritive value is very high in comparison with other food including animal-derived fermented foods such as salted fish guts, and is particularly nutritive in terms of calcium supply. However, the mechanism of calcium solubilization in kimchi is not yet clearly understood. In this study, calcium was divided into four chemical fractions and its change was examined. The relationship of calcium with other ingredients was also investigated during kimchi storage. A good temperature for kimchi storage is 4 °C from the point of view of pH and acidity. Calcium showed change in concentration regardless of storage temperatures ; however the calcium concentration in the water-soluble fraction decreased in the earlier period of storage and that in the sodium chloride-soluble fraction increased. From these results, it is desirable to eat immediately after purchase to take advantage of the high calcium. The softening of the texture of kimchi may be prevented because the concentration of calcium content mixed with pectin is high.

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