Cigar tobacco leaves (CTLs) contain abundant bacteria and fungi that are vital to leaf quality during fermentation. In this study, artificial fermentation was used for the fermentation of CTLs since it was more controllable and efficient than natural aging. The bacterial and fungal community structure and composition in unfermented and fermented CTLs were determined to understand the effects of microbes on the characteristics of CTLs during artificial fermentation. The relationship between the chemical contents and alterations in the microbial composition was evaluated, and the functions of bacteria and fungi in fermented CTLs were predicted to determine the possible metabolic pathways. After artificial fermentation, the bacterial and fungal community structure significantly changed in CTLs. The total nitrate and nicotine contents were most readily affected by the bacterial and fungal communities, respectively. FAPROTAX software predictions of the bacterial community revealed increases in functions related to compound transformation after fermentation. FUNGuild predictions of the fungal community revealed an increase in the content of saprotrophic fungi after fermentation. These data provide information regarding the artificial fermentation mechanism of CTLs and will inform safety and quality improvements.
In order to develop the high‐temperature‐released pyrrole aroma, two novel flavors precursors of methyl 2‐methyl‐5‐(((2‐methylbutanoyl)oxy)methyl)‐1‐propyl‐1H‐pyrrole‐3‐carboxylate and methyl 2‐methyl‐5‐(((2‐methylbutanoyl)oxy)methyl)‐1‐propyl‐1H‐pyrrole‐3‐carboxylate were synthesized using glucosamine hydrochloride and methyl acetoacetate as raw materials through cyclization, oxidation, alkylation, reduction, and esterification. The target compounds were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), infrared spectroscopy (IR) and high‐resolution mass spectrometry (HRMS). Thermogravimetry (TG), differential scanning calorimeter (DSC) and the pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) methods were used to analyze the heating‐stability of the target compounds, and the pyrolysis mechanism was inferred. Py‐GC/MS results indicated that some fragrance compounds were formed during thermal degradation such as 2‐methylbutyric acid, 2‐methylbutyrate, alkylpyrroles, and benzoic acid, which were important aroma components or flavor additives. This provided a theoretical reference for the application of pyrrole ester in cigarette and heat‐processed food flavoring.
in Wiley Online Library (wileyonlinelibrary.com).Glucosamine hydrochloride 1 was treated with 1,3-dicarbonyl compounds to obtain 2-methyl-5-(1,2,3,4tetrahydroxy-butyl) pyrrole 2a and 2b, respectively. Under the role of NaIO 4 , 2a and 2b were successfully transformed into the related 5-formal pyrrole derivative 3a and 3b, respectively. Compounds 4a-4d and 5a-5e were obtained by reacting 3a and 3b with chlorinated hydrocarbons by alkylation reactions, respectively. The structures of all new products were confirmed by IR, NMR, and HRMS spectra.
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