Abstract:

A rapid and simple method was developed for the determination of volatile flavor compounds (VFCs) in soy sauce by head space solid-phase microextraction (HS-SPME) coupled to capillary gas chromatography-mass spectrometry (GC-MS). Five types of SPME fibers, including 85 μm PA, 100 μm PDMS, 75 μm CAR/PDMS, 65 μm PDMS/DVB, 50 μm DVB/CAR/PDMS were investigated. Three parameters for HS-SPME in terms of adsorption time, salt concentration, and extraction temperature were optimized. Adsorption time tested in this study were 20, 40 and 60 minutes; the salt concentrations were 180, 210, 250, 270 and 300 g/L; and extraction temperatures were 25, 35, 45, 55 and 65 ℃. The concentrations of the compounds were calculated based on their relative peak areas to the internal standard of 2-octanol. An 85 μm PA fiber, adsorption time of 40 min, a temperature of 45 ℃ and NaCl concentration of 250 g/L were selected as th optimum conditions. This optimized method was applied to evaluate a real sample. As a result, 97 compounds in a soy sauce sample were isolated and identified successfully. The results showed that alcohols, carboxylic acids, esters and phenols were the major VFCs of soy sauce. The most important groups of volatile compounds in the soy sauce sample were ethanol, hexadecanoic acid, phenylethyl alcohol and 2,3-butanediol. In addition, some oxo-compounds and heterocyclic compounds were also found. The average relative standard deviation of the relative peak area was 12.1%, and the recoveries were 79.9%-109.6%. The method is simple, fast and accurate with high reproducibility, high sensitivity and low cost.

Key words: gas chromatography-mass spectrometry (GC-MS), soy sauce , volatile flavor compounds (VFCs), head space solid-phase microextractions (HS-SPME)