香菇真空冷冻干燥过程中含硫风味物质的形成机理

Shiitake mushroom is one of the most common consumed edible mushrooms in our country due to its delicious taste, fragrant flavor and abundant nutrition features. Dried Shiitake mushroom is considered as the major processed product with its quality deeply affected by the drying methods, especially the flavor characteristics. The present research aims at investigating the Sulphur-compounds formation of the dried Shiitake mushroom flavor components during the vacuum freeze-drying process, particularly the forming pathway of Lenthionine. The action mechanisms of Maillard reaction, effect of glutamyl transpeptidase (GGT) and cysteine sulfoxide lyase (C-Slyase) on the Sulphur-compounds formation will be studied through the enzyme deactivation comparation, Shiitake mushroom organization structure observation, temperature and moisture detection, GGT and C-Slyase activities tracking, and the Maillard reaction products change rules analyzation, mainly the sulfur substrate and S-containing flavor compounds such as Lenthionine, from which the present study will reveal the formatting mechanisms of the S-containing flavor compounds of Shiitake mushroom during the vacuum freeze-drying process, and provide crucial theoretical evidence for the dried Shiitake mushroom production and Shiitake mushroom based seasoning exploitation.

香菇味道鲜美、香味浓郁、营养丰富，是我国消费最为普遍的食用菌之一。干制是香菇的主要加工方式，而干燥方式与干香菇品质密切相关，尤其是对产品风味具有重要的影响。本项目在前期研究基础上，从真空冷冻干燥过程出发，针对风味物质的含硫化合物的形成，尤其是干香菇关键特征风味物质香菇精的形成途径，通过灭酶处理对比、香菇组织结构、温度、水分含量变化和谷氨酰转肽酶（GGT）和半胱氨酸亚砜裂解酶（C-Slyase）活性跟踪，美拉德反应含硫底物及相关产物、香菇精等含硫风味物质变化规律分析，研究香菇真空冷冻干燥过程中美拉德反应、GGT和C-Slyase酶对含硫风味物质影响的作用机制，揭示香菇真空冷冻干燥过程中含硫风味物质的形成机理，为香菇干制以及以香菇为基料的调味品开发提供重要的理论依据。

香菇味道鲜美，香味浓郁，是我国消费最为普遍的食用菌之一。干制是香菇的主要加工方式，而干燥方式与干香菇品质密切相关，尤其是对产品风味具有重要的影响。本项目研究了不同干燥方式对香菇理化品质和风味物质变化的影响，基于电子鼻和GC-IMS建立了挥发性物质指纹图谱，基于电子舌和HPLC研究了非挥发性物质的变化规律；动态追踪真空冷冻干燥过程中香菇的γ-GGT酶和C-Slyase酶活性、重要挥发性含硫物质以及美拉德底物变化的规律，从美拉德反应和酶促反应两个角度探究香菇的挥发性含硫物质形成机制。结果发现，(1)与热风干燥（HD）和真空冷冻联合热风干燥（VFD-HD）相比，真空冷冻干燥（VFD）香菇中的果糖和酒石酸含量最高，含硫挥发性物质含量最低；(2)VFD干燥时将解析温度升高至50℃，有利于形成含硫挥发性物质以及消耗L-半胱氨酸和果糖；(3)香菇的γ-GGT酶和C-Slyase酶与部分含硫挥发性物质间呈显著负相关关系，γ-GGT酶在香菇解析干燥末期阶段出现第二次激活态，此时大量形成CS2、香菇精等杂环含硫物质及二甲基二硫醚，且还原糖和L-半胱氨酸含量显著减少(p<0.05)；(4)香菇灭酶后，解析干燥末期几乎不再生成挥发性含硫物质，还原糖含量显著增加 (p<0.05)，L-半胱氨酸含量变化不显著(p>0.05)。以上结果表明，香菇中挥发性含硫物质形成主要依赖酶反应途径而不是美拉德反应过程，且在解析阶段升高温度有利于促进酶的反应。