Profile of Volatile Compounds in 12 Chinese Soy Sauces Produced by a High-Salt-Diluted State Fermentation

There have been limited studies on the flavour compounds in Chinese soy sauces. In order to obtain wider information about the chemical composition of the volatile fractions in 12 brands of Chinese soy sauces produced by high-salt-diluted state fermentation (HSDSF) and to compare them, a headspace solid microextraction method coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) method was proposed and developed. A 50/30μm Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) fibre was used for extraction of volatiles. The adsorption time and temperature of the SPME fibre were optimized separately for various aroma compounds in the soy sauce (50°C and 40 min for alcohols and esters; 40°C and 50 min for ketones, aldehydes and pyrazines; 60°C and 50 min for acids, phenols and furans). From the study, a total of 80 compounds were identified in the 12 samples, of which 34 volatiles were in common. Alcohols and acids were the main volatiles present in the soy sauces. Dominant volatile alcohols were ethanol, 2/3-methyl butanol and β-phenylethyl alcohol; and important acids were acetic acid, butanoic acid, and 3-methylbutanoic acid. Miscellaneous, esters, furans and phenols also made large contributions to the total volatiles of the soy sauces. According to the scatter point plot obtained from principal component analysis, the 12 soy sauces could be classified into four groups.