61B-15 |
Volatile compounds in Chinese fermented soybeans (Glycine max) ¡V douchi |
A. P. S. CHANG, Food and Nutritional Sciences Programme, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China and H. Y. Chung, Biology Dept., Food and Nutritional Sciences Programme, and Food Sci. Lab., The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China. Douchi, also called salted black beans, is a fermentation product of the mold Aspergillus oryzae on whole soybeans Glycine max. It is a seasoning ingredient popular in Chinese dishes. Similar products exist in other Oriental countries like Japan (e.g. hamanatto) and the Philippines (e.g. tao-si). Due to the similarities of douchi's manufacture to the primary production steps of soy sauce and miso, little information regarding douchi and its volatile quality is available in the scientific literature. In this study, we attempted to identify the volatile profile of douchi. Douchi samples were purchased from a local marketplace in Hong Kong. They were heated up to 60¢XC under a continuous stream of nitrogen in a closed glass container. The headspace volatile compounds were collected by a Tenax trap and later eluted with re-distilled diethyl ether. The concentrated eluant was injected into a gas chromatography/mass spectrometry (GC/MS) for analysis. Twenty-seven volatile compounds from douchi were identified and quantified. Among them were 4 alcohols, 2 aldehydes, 1 ketone, 1 ester, 4 pyrazines, 8 acids, 2 benzenes and 5 other compounds. Acetic acid, 3-methylbutanoic acid, 2-methylpropanoic acid, ethyl acetate, butylated hydroxytoluene (BHT), 2-butanone, ethanol, and methylpyrazine were present in the largest quantities. Volatile compounds commonly found in the aroma makeup of soy sauce and miso include ethyl acetate, 2-butanone, ethyl propanate, 2-butanol, 2-methyl-1-propanol, 2-methylhexanol, acetoin, 2,5-dimethylpyrazine, ethyl butyrate, benzyl alcohol, phenols and phenyl ethyl alcohol. Douchi shares some of these common volatile compounds. The identification of douchi volatile compounds not only furthers our understanding of the fermentative action on soybeans, it also allows us to make comparison with the quality of other fermented soy condiments like soy sauce, sufu (Chinese cheese) and Chinese jiang.
Session 61B, Food Chemistry: Flavor and aroma chemistry
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