The internal microbial diversity and small molecular metabolites of Nuodeng ham in different processing years (the first, second and third year sample) were analyzed by high-throughput sequencing technology and gas chromatography-time of flight mass spectrography (GC-TOF-MS) to study the effects of microorganisms and small molecular metabolites on the quality of ham in different processing years. The results showed that the dominant bacteria phyla of Nuodeng ham in different processing years were Proteobacteria and Firmicutes, the dominant fungi phyla were Ascomycota and Basidiomycota, while Staphylococcus and Aspergillus were the dominant bacteria and fungi of Nuodeng ham, respectively. Totally, 252 kinds of small molecular metabolites were identified from Nuodeng ham in different processing years, and 12 different metabolites were screened through multivariate statistical analysis. Further metabolic pathway analysis showed that 23 metabolic pathways were related to ham fermentation, of which 8 metabolic pathways had significant effects on ham fermentation (Impact > 0.01, P < 0.05). The content of L-proline, phenyllactic acid, L-lysine, carnosine, taurine, D-proline, betaine and creatine were significantly positively correlated with the relative abundance of Staphylococcus and Serratia, but negatively correlated with the relative abundance of Halomonas, Aspergillus and Yamadazyma.

The quality characteristics of dry-cured hams from different regions of Yunnan province were studied by analyzing five types of Yunnan dry-cured hams (Xuanwei ham, Sanchuan ham, Nuodeng ham, Saba ham, and Heqing ham) using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The analysis aimed to identify different volatile organic compounds (VOCs) in the dry-cured ham samples. Forty-one VOCs were qualitatively characterized by HS-GC-IMS from dry-cured ham samples, of which Nuodeng ham and Saba ham had similar fingerprint profiles and contained higher levels of aldehydes and alcohols. Meanwhile, a total of 12 qualitatively differential characteristic markers were screened by the PLS-DA model. Furthermore, 128 main VOCs were identified by HS-SPME-GC-MS, of which 26 differential characteristic markers were screened by the PLS-DA model. HCA analysis showed that the VOCs of Sanchuan ham were different from those of the other four dry-cured hams due to the unique processing. These results can contribute to a more comprehensive understanding of the flavor characteristics of dry-cured hams from different regions of Yunnan.