Comparison of volatiles profile in soy sauce according to inoculated microorganisms and salt contents during brine fermentation

Abstract

This study was conducted to demonstrate volatiles profile of soy sauce according to different conditions of brine fermentation; (1) inoculated with Tetragenococcus halophilus or Zygosaccaromyces rouxii, and (2) added with different salt contents. A total of 110 and 85 volatiles were identified using SPME and solvent extraction, respectively. The volatile compounds extracted by SPME were mainly composed of esters, low molecular aldehydes and ketones, whereas predominant volatile compounds isolated by solvent extraction were acids, high molecular aldehydes and furanes. Principle component analysis (PCA) was applied to gas chromatography-mass spectrometry (GC-MS) data sets to discriminate soy sauce samples. Soy sauce samples treated with T. halophilus and Z. rouxii could be separated, but it was difficult to see difference according to levels of inoculation size on PCA plots. Major volatile compounds contributing to the samples treated with T. halophilus were mainly acetic acid, formic acid, benzaldehyde, methyl acetate, ethyl 2-hydroxypropanoate, 3-(methylthio)-propanoic acid, 2-hydroxy-3-methyl-2-cyclopenten-1-one, and 4-hydroxy-3-methoxybenzaldehyde. On the other hand, volatile compounds contributing to the samples inoculated with Z. rouxii were mainly ethanol, acetaldehhyde, ethyl propanoate, 2/3-methylbutanol, 1-butanol, 2-phenylethanol, ethyl 2-methylpropanoate, and 4-hydroxy-2-ethyl-5-methyl-3(2H)-furanone (HEMF). Regarding the effect of salt contents on the volatiles profile, as the contents of salt decreased, more diverse volatile compounds could be found in soy sauces. Major volatile compounds closely related to the samples treated by low salt solution (below 16%) were mainly ketones, such as 2,3-butanedione, 3-hydroxy-2-butanone, 2-heptanone, and 3-methyl-2-butanone, esters, such as methyl acetate, 2-methylpropyl acetate, 3-methylbutyl acetate, and 2-methylbutyl acetate, acids, such as propanoic acid, 2-phenylacetic acid, and 3-(methylthio)-propanoic acid, and others. Most diverse compounds, including lipid oxidation products, were observed in the sample containing the lowest salt content (LY10). However, some ethyl esters, such as ethyl octanoate, ethyl dodecanoate, ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, ethyl phenylacetate, ethyl benzoate, and ethyl hydrogen succinate, and 3-(methylthio)-propanal relatively highly contributed to LY13 and LY16 than LY10. LY19 were closely related to some compounds, such as acetaldehyde, 2-ethyl-2-butenal and HEMF, which were major volatile compounds of soy sauce samples inoculated with Z. rouxii. In contrast, the samples cultivated under the highest salt concentration (21 %) had less sufficient volatile compounds compared to others.;본 연구에서는 간장 제조 중 담금 과정에 있어서 접종되는 미생물의 종류 (Tetragenococcus halophilus 와 Zygosaccaromyces rouxii) 와 염수 농도에 따라 나타나는 간장의 휘발성 성분의 차이를 규명하고자 하였다. 간장의 휘발성 성분을 프로파일링하기 위하여 고체상미세추출법 (solid-phase microextraction) 과 용매추출법(solvent extraction) 을 이용하여 휘발성 성분을 추출하고, 가스 크로마토그래피- 질량분석법 (gas chromatography-mass spectrometry)으로 분석하였으며, 주성분분석법 (principle component analysis) 을 수행하여 시료에 따른 차이를 비교 분석하였다. 담금 과정 초기에 접종된 T. halophilus 와 Z. rouxii 에 따라 간장의 휘발성 성분에 차이를 나타내었으며, 시료 간 차이에 기여한 주요 성분은 acetic acid, formic acid, benzaldehyde, methyl acetate, ethyl 2-hydroxypropanoate, 3-(methylthio)-propanoic acid, 2-hydroxy-3-methyl-2-cyclopenten-1-one, 4-hydroxy-3-methoxybenzaldehyde, ethanol, acetaldehhyde, ethyl propanoate, 2/3-methylbutanol, 1-butanol, 2-phenylethanol, ethyl 2-methylpropanoate, 4-hydroxy-2-ethyl-5-methyl-3(2H)-furanone (HEMF) 으로 나타났다. 담금 과정에 이용되는 염수의 농도는 간장의 휘발성 성분에 영향을 주었으며, 소금의 농도가 감소할수록 더욱 다양한 휘발성 성분이 간장에 기여하는 경향을 나타내었다. 16% 이하의 염수 농도에서 발효된 간장에 기여한 성분들은 2,3-butanedione, 3-hydroxy-2-butanone, 2-heptanone, and 3-methyl-2-butanone의 케톤류와 methyl acetate, 2-methylpropyl acetate, 3-methylbutyl acetate, 2-methylbutyl acetate 등의 에스테르류, propanoic acid, 2-phenylacetic acid, 3-(methylthio)-propanoic acid 등의 성분들로 나타났다. 가장 낮은 농도의 염수 (10%)를 이용한 간장 시료에서 지방산화물을 포함하여 가장 많은 휘발성분들이 동정되었으나, 일부 에스테르 성분들 (ethyl esters, such as ethyl octanoate, ethyl dodecanoate, ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, ethyl phenylacetate, ethyl benzoate, ethyl hydrogen succinate) 은 LY13과 LY16에 더 많이 기여하는 것으로 나타났다. LY19에서는 Z. rouxii의 영향으로 나타났던 성분들 (acetaldehyde, 2-ethyl-2-butenal, HEMF)이 차이에 기여하였다. 반대로 가장 높은 농도의 염수 (21%) 를 이용한 간장 시료에서는 대부분의 휘발성 성분들은 상대적으로 낮게 나타났다.