Investigation on changes of volatile components in kimchi during fermentation using targeted and non-targeted approaches

Abstract

In this study, changes of volatile components in baechu kimchi according to fermentation periods were elucidated using both targeted and non-targeted analysis. Solid phase microextraction (SPME) was used to extract volatiles in kimchi during 40 days fermentation. For targeted analysis, 8 odor-active components including methanethiol, 2-propen-1-thiol, acetic acid, allyl methyl sulfide, ethyl butanoate, 2,5-dimethylthiophene, allyl methyl disulfide and dimethyl trisulfide were determined by gas chromatography-olfactometry (GC-O) and quantified by gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM) mode. Among them, acetic acid, ethyl butanoate and dimethyl trisulfide increased as ripening proceeded, whereas the other sulfur-containing odorants showed no change or decreased during fermentation periods. In non-targeted analysis, volatiles in baechu kimchi were determined by GC-MS and organized by automated mass spectral deconvolution and identification system (AMDIS). As multivariate analysis, principle component analysis (PCA) was conducted to visualize and summarize the obtained data sets during fermentation of baechu kimchi. As results, the dominant components were identified depending on a degree of ripening. Sulfur-containing compounds, including diallyl sulfide, 2-ethylthiophene, allyl isopropyl sulfide, 2,5-dimethylthiophene, di(1-propenyl) sulfide, 1,3,5-trithiane, 3-vinyl-1,2-dithiacyclohex-4-ene, thieno[3,2-b]thiophene, 1,2,4,6-tetrathiepane, 2-butenal, 6-methylhept-5-en-2-one and p-cymene contributed to early stage of kimchi fermentation. On the other hand, acetic acid, 1-penten-3-one, ethyl 2-butenoate, methyl (methylthio)methyl disulfide, 2-isothiocyanatoethylbenzene and dimethyl trisulfide were found to be contributors to latter stage of the fermentation of kimchi.;본 연구에서는 발효 기간에 따른 배추김치의 휘발성 성분을 targeted와 non-targeted 기법을 이용하여 규명하고자 하였다. 40일 간의 발효 기간 동안 배추김치의 휘발성 성분을 추출하기 위해 고체상미세추출법 (Solid phase microextraction, SPME)를 이용하였다. Targeted 분석 기법에서는 gas chromatography-olfactometry (GC-O)를 이용하여, methanethiol, 2-propen-1-thiol, acetic acid, allyl methyl sulfide, ethyl butanoate, 2,5-dimethylthiophene, allyl methyl disulfide and dimethyl trisulfide 등 8개의 향기활성성분들을 규명하였고, gas chromatography-mass spectrometry (GC-MS)의 selected ion monitoring (SIM) mode를 이용하여 정량분석하였다. 이 중에서 발효 산물인 acetic acid, ethyl butanoate, dimethyl trisulfide는 숙성에 따라 증가하였으며, 나머지 황함유 향기활성성분은 숙성 기간이 증가함에 따라 줄어들거나 변화가 없었다. Non-targeted 분석 기법에서는 GC-MS와 automated mass spectral deconvolution and identification system (AMDIS)를 이용하여 김치의 향미성분을 규명하였으며, 숙성 기간에 따른 차이와 이에 기여하는 성분을 알아보기 위해, 다변량통계분석법인 principle component analysis (PCA)를 수행하였다. 그 결과, 황함유화합물인 diallyl sulfide, 2-ethylthiophene, allyl isopropyl sulfide, 2,5-dimethylthiophene, di(1-propenyl) sulfide, 1,3,5-trithiane, 3-vinyl-1,2-dithiacyclohex-4-ene, thieno[3,2-b]thiophene, 1,2,4,6-tetrathiepane, 3,4-dicyanothiophene와 2-butenal, 6-methylhept-5-en-2-one, p-cymene 가 김치의 숙성 초기에 기여하는 성분들로 밝혀졌고, acetic acid, 1-penten-3-one, ethyl 2-butenoate, methyl (methylthio)methyl disulfide, 2-isothiocyanatoethylbenzene, dimethyl trisulfide 가 김치의 숙성 후기에 기여하는 향미성분으로 밝혀졌다.