Shintaro Moritaka

Studies on Cereals

Five carbonyl compounds were found in the vapour of cooked rice, of which acetaldehyde, and n-caproaldehyde were identified from their retention times in gas chromatography and by their infrared spectra. Propionaldehyde or acetone, methylethylketone, and n-valeraldehyde were tentatively identified. The mechanisms of the formation of these carbonyl compounds were discussed from the view-point of Strecker degradation and lipid oxidation.When stored rice (40°C, two months) was cooked, the stale flavor (komai-shu) was clearly detected by sensory test. Direct gas chromatographic analysis of head space vapors over cooked rice showed three main peaks which corresponded to propionaldehyde or acetone, n-valeraldehyde and n-caproaldehyde. On the other hand, the content of linoleic and linolenic acids of the rice decreased during storage at 40°C. This means that the unsaturated fatty acids autoxidized during storage and gave rise to carbonyl compounds responsible for the stale flavor of cooked rice.

Relation between Lipid Content of Milled Rice and Deterioration of Rice Flavors during Storage:Studies on Cereals (Part 7)

n-ヘキサン処理の条件を変え脂質含量の異なる精白米を調製した。肪質含量と米飯食味との間に一定の傾向は認められない。しかし脂質含量が少ないほど貯蔵中の品質劣化が少ないことを官能検査およびテクスチュロメーターの測定により明らかにした。