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

摘要： 为了探明密集烤房保温处理对烟叶烘烤过程中蛋白质降解和氮代谢的影响，采用2种能源类型（空气源热泵、生物质燃烧）与2种保温材料（聚氨酯、无机塑化微孔）交叉组合，设置4个处理，分别为聚氨酯保温空气源热泵烤房（CK1）、聚氨酯保温生物质烤房（CK2）、无机塑化微孔保温空气源热泵烤房（T1）和无机塑化微孔保温生物质烤房（T2）。通过测定烘烤过程中烟叶的蛋白质含量、氨基酸含量、氮代谢相关酶（内肽酶、氨肽酶、羧肽酶）活性及烤后烟游离氨基酸含量，分析不同保温处理对烟叶烘烤过程中氮代谢的影响规律。结果表明，在烘烤42 ℃时，T1、T2处理的蛋白质降解率分别为38.59%、37.26%，较CK1、CK2 处理分别提高了6.99、6.39 百分点；在烘烤40~42 ℃时，T1、T2 处理氨基酸变化幅度分别为31.13%、34.60%，均高于CK1和CK2处理，且烤后烟中游离氨基酸含量明显提高了71.14%、47.47%，其中，甜味氨基酸含量分别提高了80.61%、52.00%，比例分别提高了4.01、2.26百分点。T1、T2处理在烘烤变黄期38~42℃的平均内肽酶活性为2.71、2.70 U/mL，平均羧肽酶活性为210.88、204.10 U/mL，平均氨肽酶活性为187.27、186.89 U/mL，均高于CK1、CK2处理。T1处理的氨肽酶活性峰值和T2处理的羧肽酶和氨肽酶活性峰值提前出现至40 ℃，有利于烟叶在变黄期（38~42 ℃）充分进行含氮物质转换和降解。通径分析结果表明，对含氮物质的转化和分解起主要作用的是氨肽酶，其次是羧肽酶。主成分分析结果表明，苯丙氨酸、谷氨酸、丙氨酸和酪氨酸等氨基酸对烤后烟风味具有较大贡献，T1和T2处理烤后烟呈味氨基酸综合得分高于CK1和CK2处理。综上，无机塑化微孔保温处理后的密集烤房能够优化烟叶的烘烤环境，提高氮代谢相关酶活性，促进蛋白质降解和氨基酸积累，并提高烤后烟的香气量、改善香气质。

关键词: 烟叶, 密集烤房, 保温材料, 蛋白质, 氨基酸, 氮代谢