Abstract: Long-chain fatty acids (LCFAs) and long-chain fatty acid ethyl esters (LCFAEEs) are key substances that influence the flavor quality and stability of Baijiu. However, the complex matrix of fermented grains introduces significant interferences, making the accurate quantification of target compounds challenging. In this study, a gas chromatography-tandem mass spectrometry method was established for the targeted detection of LCFAs and LCFAEEs in fermented grains. Samples were extracted using n-heptane ultrasonically for 60 min, followed by derivatization treatment for 30 min. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode. Quantification of the analytes was performed using both internal and external standards. The results showed that the calibration curves for the 18 target compounds exhibited good linearity within the tested concentration ranges (R2 > 0.99), with detection limits ranging from 0.33 to 533.60 μg/L and quantification limits from 1.11 to 1 778.66 μg/L. The average recoveries for spiked sample ranged from 81.22% to 113.67%, with relative standard deviations between 3.22% and 12.55%, indicating high sensitivity, accuracy, and precision of the method. Analysis of fermented grains from various fermentation rounds using this method revealed that ethyl oleate, ethyl linoleate, and ethyl palmitate accumulated continuously during the fermentation process, with accelerated accumulation after the 4th round. By the 7th round, the contents of these three ethyl esters reached up to 245.39, 729.79, and 161.65 mg/100 g, respectively. The proposed method features simple pretreatment procedures and high accuracy, providing a reliable tool for the efficient detection of trace ethyl esters in complex fermentation systems.

Key words: jiupei; long-chain fatty acids; long-chain fatty acid ethyl esters; multiple reaction monitoring mode; gas chromatography-tandem mass spectrometry