香菇热风干燥过程中含硫氨基酸与含硫香气成分生成关系及分子机制研究

Fresh shiitake mushroom (Lentinula edodes) is difficult to preserve quality and usually processed by hot air drying. After hot air drying, the contents of sulfur-containing aroma compounds increase and specific aroma quality appears. The researches about the formation of sulfur-containing aroma-active compounds in shiitake mushrooms always focus on the lenthinic acid as the precursor. Up to now, there has been no research about the sulfur-containing amino acids as the precursors. The mechanism of the aroma formation in shiitake mushrooms during drying could not be revealed. On the basis of identification and quantification of aroma compounds and amino acids in shiitake mushrooms during the treatment of hot air drying, this research will focus on the relation between the sulfur-containing amino acids and the formation of sulfur-containing aroma compounds and its molecular mechanism. Firstly, the changes of sulfur-containing amino acids and the formation of sulfur-containing aroma-active compounds will be investigated, in order to conform the relation between the sulfur-containing amino acids and the formation of sulfur-containing aroma-active compounds. Then the sulfur-containing amino acid precursors will be confirmed, through stable isotope dilution analysis (SIDA) and high-resolution mass spectrometry in model system and situ system. Finally, the reaction pathway and molecular mechanism of the formation of sulfur-containing aroma-active compounds with the sulfur-containing amino acids as precursors will be revealed, through the fragment ion information and specific isotope labeled technique. This study is significant to reveal the formation mechanism of characteristic aroma of shiitake mushroom and will promote the flavor study of edible mushrooms and flavor quality of edible mushroom products in the food industry.

新鲜香菇不易贮存，多采用热风干燥进行加工。干燥后，香菇含硫香气成分增加，产生独特风味。目前，香菇含硫香气成分的形成机制研究多集中在以香菇酸为前体物质的研究，这不足以揭示香菇特征香气形成机制。在热风干燥过程中香菇的香气成分和氨基酸定性定量研究基础上，本项目重点研究香菇热风干燥过程中含硫氨基酸与含硫香气成分生成关系及分子机制。首先，通过研究干燥过程中含硫氨基酸组成变化规律与含硫香气成分生成规律，确定含硫氨基酸与含硫香气成分生成关系；随后，通过体外模拟体系和原位复杂体系，利用高分辨质谱和稳定性同位素稀释法，确定含硫氨基酸前体物质；最后，通过碎片离子信息、稳定性同位素元素归属和同位素标记示踪，揭示含硫氨基酸生成含硫香气成分的反应途径和分子机制。预期成果对解析香菇特征风味形成机制具有重要意义，也为食用菌风味研究和产品风味品质提升提供理论依据。

生产加工中，新鲜香菇多采用热风干燥处理，其产品不仅易贮藏，还具有独特的风味，主要为含硫风味。目前，香菇含硫香气成分的形成机制研究多集中在以香菇酸为前体物质的研究，这不足以揭示香菇特征香气形成机制。本项目基于食品风味组学、稳定性同位素分析、高分辨质谱分析、多维数据分析、模拟体系分析、原位复杂体系分析，重点研究香菇热风干燥过程中含硫氨基酸与含硫香气成分生成关系及分子机制。首先，利用气相色谱-离子迁移谱联用、气相色谱-质谱联用结合描述性感官分析，鉴定了热风干燥香菇的风味轮廓和含硫风味指纹图谱，发现干燥程度对香菇风味轮廓影响较大。其次，基于分子感官科学、标准曲线构建、重组模型分析，鉴定了新鲜香菇中关键性含硫香气成分3-甲硫基-丙醛、3-甲硫基-丙醇、香菇素，热风干燥香菇中关键性含硫香气成分二甲基三硫醚、3-甲硫基-丙醛、香菇素，明确了其香气活性值和干燥过程中的变化；基于稳定同位素分析、高效液相色谱-三重四极杆质谱联用分析、多维数据分析，明确了香菇中氨基酸和还原糖在干燥过程中的变化，研究发现蛋氨酸可能是二甲基三硫醚和香菇素的前体物质；半胱氨酸可能是香菇素的前体物质，核糖可能是与蛋氨酸和半胱氨酸发生美拉德反应的还原糖；通过体外模拟体系、鉴物质结构、精确定量，确定蛋氨酸和核糖是二甲基三硫醚的前体物质，蛋氨酸和半胱氨酸都不是香菇素的前体物质；基于原位复杂体系，进一步验证了蛋氨酸和核糖是二甲基三硫醚的前体物质，蛋氨酸可自身反应生成二甲基三硫醚，也可与核糖通过美拉德反应生成二甲基三硫醚，且香菇体系内酶影响了二甲基三硫醚生成速率，其动力学关系均符合多项式非线性拟合。本研究对解析香菇特征风味形成机制具有重要意义，也为食用菌风味研究提供了系统的风味组学方法。