关键词: 烟叶, 密集烤房, 保温材料, 蛋白质, 氨基酸, 氮代谢

Abstract: To investigate the effects of thermal insulation treatment in bulk curing barns on the degradation of protein and nitrogen metabolism during the tobacco leaf curing process，a cross‐combination of two types of energy source（air‐source heat pumps，biomass combustion） and two heat preservation materials（polyurethane， inorganic plasticized microporous） was used to set up four treatments：polyurethane‐insulated air‐source heat pump curing barn（CK1），polyurethane‐insulated biomass curing barn（CK2），inorganic plasticized microporous‐insulated air‐source heat pump curing barn（T1），and inorganic plasticized microporous‐insulated biomass curing barn（T2）.The protein content，amino acid content， activities of nitrogen metabolism related enzymes（endopeptidase，aminopeptidase，carboxypeptidase）during the roasting process and free amino acid content of post‐baking tobacco were measured to analyze the effects patterns of different heat preseration treatments on nitrogen metabolism during baking.The results showed that at 42℃ during curing，the protein degradation rates of T1 and T2 treatments were 38.59% and 37.26%，respectively，which were 6.99 and 6.39 percentage points higher than CK1 and CK2 treatments，respectively. During the curing period at 40—42℃ ，the amino acid variation amplitude of T1 and T2 treatments were 31.13% and 34.60%，respectively，both higher than those of CK1 and CK2 treatments，and the free amino acid content in cured tobacco significantly increased by 71.14% and 47.47%，among which the content of sweet amino acids increased by 80.61% and 52.00%，and ratio increased by 4.01 and 2.26 percentage points，respectively.The average endopeptidase activities of T1 and T2 treatments during the yellowing period of curing at 38—42℃ were 2.71 U/mL and 2.70 U/mL，the average carboxypeptidase activities were 210.88 U/mL and 204.10 U/mL，and the average aminopeptidase activities were 187.27 U/mL and 186.89 U/mL，all higher than those of CK1 and CK2 treatments.The peak activity of aminopeptidase in T1 treatment and the peak activities of carboxypeptidase and aminopeptidase in T2 treatment appeared early at 40℃ ，which was conducive to the sufficient conversion and degradation of nitrogen‐containing substances in tobacco leaves during the yellowing period（38—42℃）.Path analysis results indicated that aminopeptidase played the main role in the conversion and decomposition of nitrogen‐containing substances，followed by carboxypeptidase.Principal component analysis results showed that amino acids such as phenylalanine，glutamic acid，alanine，and tyrosine made significant contributions to the flavor of cured tobacco.The comprehensive scores of flavor amino acids in the cured tobacco of treatments T1 and T2 were higher than those of treatments CK1 and CK2.In conclusion，bulk curing barns with inorganic plasticized microporous heat preservation treatment can optimize the curing environment of tobacco leaves.This optimization is conducive to enhancing the activities of enzymes related to nitrogen metabolism，and promoting protein degradation and amino acid accumulation.As a result，it increases the aroma quantity and improves the aroma quality of cured tobacco.

Key words: Tobacco, Bulk curing barn, Insulation materials, Protein, Amino acid, Nitrogen metabolism