热风脱水苹果片美拉德反应特征性香气形成机制研究

Aroma is one of the key sensory qualities for dehydrated apple slices. Currently, researches are mainly focused on analysis of the varieties and tendency of aroma compounds in dehydrated apple slices’. Few researches reported on aroma formation mechanism in Maillard Reaction during thermal dehydration processes. In the previous studies, differences in aroma of different varieties and Maillard Reaction precursors changing regular in hot-air dehydrated apple slices have been conducted. In this project, hot-air dehydration process of apple slices will take as a typical example, solid-phase microextraction combined gas chromatography-mass spectrometry will be applied to identify aroma compounds constitute and contents. Through calculating the thresholds and conducting aroma reconstitution experiments and omission test, the Maillard Reaction characteristic aroma compounds will be identified. High performance liquid chromatography will be employed to explore the change regular of Maillard Reaction precursors, thus deduce the theoretical precursor components and verify in the model system. Moreover, isotope standard substance or 13C-labeled precursors will be used to identify the intermediate compounds of Maillard Reaction. Therefore, the Maillard Reaction characteristic aroma formation pathway will be illuminated. The purpose of this study is to clarify the effect and mechanism of Maillard Reaction precursors on characteristic aroma in hot air dehydrated apple slices and the characteristic aroma formation mechanism. The present research will provide theoretical basis for effective regulation and control the hot-air dehydrated apple slices’ aroma in Maillard Reaction.

香气是脱水苹果片重要的感官品质之一。国内外学者对脱水苹果片香气的研究多集中于分析香气种类和变化趋势，而对该过程中因美拉德反应而形成香气的机制研究较少。在前期研究不同品种苹果香气差异和热风脱水苹果片美拉德反应前体物质变化的基础上，本项目以苹果片热风脱水为典型干燥过程，采用固相微萃取-气相色谱质谱联用技术对热风脱水苹果片香气进行鉴定，结合阈值、重组试验和省略试验等确证美拉德反应特征性香气物质；采用高效液相色谱等技术，探究美拉德反应前体组分变化规律，推断理论前体物质，并在模拟体系中验证；采用同位素标准品或分子标记等手段，鉴定美拉德反应中间产物，进一步阐明美拉德反应特征性香气形成途径，从而解决热风脱水苹果片美拉德反应前体物质对特征性香气的影响及其机制和特征性香气形成机制两个科学问题，为有效调控热风苹果片美拉德反应风味提供理论基础。

本项目明确了热风脱水样品与苹果鲜样关键香气化合物存在的差异。与苹果鲜样相比，热风脱水苹果样品中，酯类和烯烃类含量降低，杂环化合物和含硫化合物种类和含量增加。电子鼻分析表明不同温度热风处理的苹果片香气轮廓存在差异。通过重组实验和省略实验确证了热风脱水苹果片的特征性香气为2-甲基丁酸己酯、正己醇、芳樟醇、苯甲醇、苯乙醇、反式-2-庚烯醛、壬醛、反式-2-壬烯醛、α-法尼烯、3-羟基-2-丁酮、6-甲基-5-庚烯-2-酮、香叶基丙酮、3-甲硫基丙醇和2-正戊基呋喃。感官评价结果表明，重组模型与热风脱水苹果片样品香气轮廓相似度均较高。通过与冻干苹果片特征性香气比较，进一步明确了芳樟醇、苯乙醇、苯甲醇、反式2-庚烯醛、反式-2-壬烯醛、3-羟基-2-丁酮、6-甲基-5-庚烯-2酮、香叶基丙酮、3-甲硫基丙醇和2-正戊基呋喃是热风脱水苹果片独有的特征性香气成分。对苹果片中美拉德反应前体物质与特征性香气成分进行相关性分析结果表明，葡萄糖、果糖和蔗糖与3-甲硫基丙醇显著负相关（P<0.05），与半胱氨酸和甲硫氨酸高度负相关。通过液态模拟体系，初步确证葡萄糖、果糖和甲硫氨酸参与3-甲硫基丙醇的形成。基于构建的固态模型，验证了3-甲硫基丙醇的前体物质为甲硫氨酸，同时确证葡萄糖和果糖促进了3-甲硫基丙醇的形成。