Apparatus Used for Small-Scale Volatile Extraction from Ethanol-Supplemented Low-Salt Miso and GC−MS Characterization of the Extracted Flavors

Abstract

An extraction apparatus was equipped with a nitrogen-flushing vessel to purge volatiles from a 10-g miso prepared solution at 40 degrees C, a reflux condenser to recover water, a coiled cold-trap to separate ethanol in advance, and a glass-lined stainless (GLS) trap filled with Tenax TA for flavor adsorption. Volatiles in the GLS tube were released with a thermal desorption device and condensed with a Micro-cryo trap prior to connection with GC and GC-MS for characterization. After analysis, a broad volatile profile comprising 9 categories of functional group and 97 identified compounds was achieved. As affected by ethanol supplementation for miso fermentation, most volatiles except alcohols and acetals in the low-salt products fermented with 5% NaCl and 7.5% ethanol were higher than those in the control products fermented with 9% NaCl and 0% ethanol and the high-ethanol supplemented products fermented with 5% NaCl and 15% ethanol. It reveals that supplementation of ethanol in miso at an appropriate level not only enabled a low-salt miso fermentation but also enhanced flavor formation.

Volatile Components in Three Commercial Douchies, A Chinese Traditional Salt-Fermented Soybean Food

“…4-Methylpentanoic acid and 8,11,14-eicosatrienoic acid(Z, Z, Z) were found in brands B and C. Some acids found in douchi have been reported in other soy products. Acetic acid, 2-methylpropanoic acid, 3-methylbutanoic acid, and hexanoic acid were found in douchi extracts, which also have previously been reported in soybean processed products such as sufu, [10,12] miso, [11] soy sauce, [14] and natto. [15] Some other compounds such as 2-methylbutanoic acid, the major flavour component of natto [17] was not found in three brands; instead its isomer 3-methylbutanoic acid was detected in three samples.…”

“…Most of the compounds identified were previously found in soybean processed products such as sufu, miso, soy sauce, and natto. [8,[10][11][12][13][14][15][16][17] According to the results obtained and the volatile compounds of other fermented soybean foods, pyrazines, esters, acids, and alcohols compounds are the important contributors to the characteristic flavour of douchies. The concentrations of volatile components in different brands of douchi were different (Fig.…”

“…Most esters have pleasant aromas and enhance douchi flavour quality. [11] Seven compounds, phenylacetic acid methyl ester, phenylacetic acid ethyl ester, 2-phenethyl acetate, hexadecanoic acid methyl ester, hexadecanoic acid ethyl ester, 9,12,15-octadecatrienoic acid(Z, Z, Z) methyl ester, and ethyl 9-octadecenoate(E) were found in all three brands.…”

“…Phenylacetic acid ethyl ester and hexadecanoic acid ethyl ester identified in three samples were also detected in sufu [8,10] and miso. [11] Ethyl acetate and ethyl propionate, which were commonly found in the aroma component of some oriental fermented products such as chungkun-jiang [15] and miso, [11] were also detected in douchi extracts. High-molecularweight fatty acid esters, such as ethyl 9-octadecenoate(E) which is likely produced by the effect of fungal lipases on soybean lipids has been reported in sufu, [8,18] and also detected in douchi extracts.…”

“…[13] It is an enzymatic derivative of linoleic acid, which has been found much higher in the low-salt miso products than in other products. [11] Having the highest concentration of components among all classes, with various unique odour characters of individual components, the alcohols could be an important class contributing to the flavour of the douchies.…”