Exploration of key aroma active compounds in strong flavor Baijiu during the distillation by modern instrument detection technology combined with multivariate statistical analysis methods

Liquid-liquid microextraction (LLME) combined with gas chromatography-mass spectrometry (GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) were used to detect the variations in volatile compounds during the distillation process of strong flavor raw Baijiu. The 3D fingerprint spectrum clearly showed a variation in volatile compounds from different distillation stages, and most alcohol-soluble and low molecular weight compounds showed a downward trend with the extension of distillation time, but water-soluble, high molecular weight and high boiling compounds showed the opposite result. Then, 50 aroma compounds were sniffed and identified by gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and multivariate statistical analysis including principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) confirmed four aroma active markers related to classification. Finally, the receiver operating characteristic (ROC) curve was further used to verify that ethyl butanoate and ethyl hexanoate were the most effective difference marker to distinguish the head Baijiu samples and butanoic acid was the most effective difference marker for distinguishing the heart Baijiu samples from the tail Baijiu samples.