Different fermentation methods on the improvement of wrapper quality and their potential mechanisms

This study compared four fermentation methods for cigar wrapper leaves (CWL): natural fermentation (NF), stacking fermentation (DJF), media fermentation (JZF), and oak barrel fermentation (XMF). The temperature, humidity, chemical composition, sensory attributes, metabolome, and proteome were analyzed. NF maintained stable but low temperature and humidity, while DJF exhibited significant temperature fluctuations and lower humidity than JZF and XMF. JZF and XMF displayed higher peroxidase and polyphenol oxidase activity, along with greater reductions in sugars, nicotine, pectin, and polyphenols compared to DJF. Metabolomic profiling identified fewer differential metabolites in DJF (405 non-volatile, 131 volatile) than in JZF (580, 231) and XMF (518, 228). Non-volatile metabolites were predominantly downregulated, while volatile metabolites were upregulated. Key metabolic pathways included terpenoid synthesis, flavonoid biosynthesis, and amino acid metabolism, contributing to cigar flavor. Proteomic analysis revealed that JZF and XMF had more downregulated (96 and 92, respectively) than upregulated (9) proteins, primarily derived from Staphylococcus and Aspergillus . In contrast, DJF showed more upregulated (67) than downregulated (30) proteins, with balanced contributions from both microbial genera. Artificial fermentation enhanced flavor diversity and conversion efficiency, with humidity being a critical regulator of microbial succession and flavor development.