Identification of characteristic flavor compounds and small molecule metabolites during the ripening process of Nuodeng ham by GC-IMS, GC–MS combined with metabolomics

To investigate effects of metabolites and volatile compounds on the quality of Nuodeng ham, gas chromatography-mass spectrometry (GC–MS), ultra-high performance liquid chromatography-Q exactive orbitrap-mass spectrometry (UHPLC-QE-MS), and gas chromatography-ion transfer spectroscopy (GC-IMS) were used to analyze the differences of free fatty acids, small molecule metabolites and volatile compounds of Nuodeng ham at different ripening stages (the first, second and third year sample). 40 free fatty acids were detected. 757 and 300 metabolites were detected in positive and negative ion modes, respectively. 48 differential metabolites (VIP ≥ 1.5, P < 0.05) might important components affecting flavor differences of Nuodeng ham. Metabolic pathways revealed that fermenting-ripening of ham was associated with 31 metabolic pathways, among, 19 pathways were significant (Impact > 0.01, P < 0.05). 58 volatile compounds were identified, combined with PCA and PLS-DA, 15 flavor markers were screened out. These findings provide a scientific basis for further research on the flavor formation mechanism of Nuodeng ham.