Effect of fermentation stages on glucosinolate profiles in kimchi: Quantification of 14 intact glucosinolates using ultra-performance liquid chromatography-tandem mass spectrometry

We developed and validated an ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry-based analytical method to determine intact glucosinolates in kimchi and evaluate the effects of fermentation stages on glucosinolate profiles. The developed method yielded reliable data in the kimchi matrix in terms of selectivity, matrix effect (88 %–105 %), linearity (coefficients of determination ≥0.9991), sensitivity (limits of quantification ≤35 nmol/L), accuracy (82 %–101 %), and precision (≤8%). The kimchi samples contained progoitrin, sinigrin, glucoraphanin, glucoraphenin, glucoalyssin, gluconapin, glucobrassicanapin, glucobrassicin, glucoberteroin, gluconasturtiin, 4-methoxyglucobrassicin, and neoglucobrassicin, of which 4-methoxyglucobrassicin, glucobrassicanapin, and gluconapin were the major compounds. Total glucosinolate content was decreased by 31 %–97 % and 91–100 % in the moderate-fermented and over-fermented samples, respectively, compared with that in the non-fermented samples, revealing sudden glucosinolate degradation between the moderate- and over-fermentation stages. In summary, we report an efficient analytical method to estimate kimchi glucosinolate profiles, which could be a foundation for future studies.