Integrated E-nose, GC-MS/GC-IMS, untargeted metabolomics, and high-throughput sequencing reveal mechanisms underlying...

This study aimed to elucidate the mechanisms underlying flavour differentiation in Xuanwei ham across different quality grades (A, B, and C), using a combined approach involving electronic nose (E-nose), gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), metabolomics, and high-throughput sequencing. The instrumental evaluation was consistent with the traditional "three sticks" grading system, confirming distinct flavour profiles for each grade. Aldehydes, particularly 3-methylbutanal and nonanal, were identified as the primary contributors to the aroma of Grade A samples. In contrast, Grade C samples were characterised by the accumulation of short-chain fatty acids, such as valeric acid and hexanoic acid. Metabolomic analysis identified 52 differential metabolites, with amino acids, fatty acids, and their derivatives serving as key metabolites distinguishing ham quality. Furthermore, pathway enrichment analysis highlighted 33 metabolic pathways associated with quality, of which eight were significant based on topological pathway impact values (impact >0.1, P < 0.05). Microbiological analysis revealed that Meyerozyma and Aspergillus were the dominant fungal genera. Multi-omics association analysis demonstrated significant positive correlations between specific fungal species (e.g., Meyerozyma amylolytica and Aspergillus fumigatus) and multiple key flavour compounds and precursor metabolites. These findings elucidate the microbial and metabolic factors influencing flavour differentiation in Xuanwei ham and provide a scientific basis for precision quality control and process optimisation.