The main irritant substance of Hatomugi, Coix Lacryma-Jobi Linné, var. Ma-yuen Stapf, was isolated. From the results of analysis of this substance by means of hydrolysis, thin layer chromatography, elementary analysis and infrared spectroscopy, the irritant substance in Hatomugi was presumed as a glucoside of 3, 4-dihydroxybenzaldehyde.
Hydrogen sulfide which seemed to contribute to the aroma of cooked rice was determined quantitatively by colorimetry, and it was found that 2 to 4μg% of hydrogen sulfide was contained in the distillate obtained during cooking rice. The effect of volatiles on the sensory quality of cooked rice was studied by comparing the GC patterns of head space vapor of tasty cooked rice of fresh crops with those of non-tasty stored rice and or with those of twice cooked rice. Total amount of volatiles from tasty cooked rice was 3 to 5 times as much as that from nontasty one. Lower boiling volatiles from fresh crops represented 80 to 90% of total aroma compounds but those from stored rice were 45%. On the other hand, carbonyls (C3-C6) from stored rice represented 30% of total aroma compounds, which corresponded to 10 times as much as those from fresh crops. Aroma concentrate of cooked rice was prepared and separated into basic, neutral and acidic fractions. Basic fraction showed the characteristic aroma of cooked rice, which was somewhat pyrazin-like and had a resemblance to the aroma produced from heated aqueous solution of proline with dihydroxyacetone.