甜瓜是极热敏性水果的典型代表，热处理引起风味劣变产生异味（off-flavor）严重影响产品感官品质。本项目基于热加工甜瓜汁蒸煮异味组分和前体物鉴别、异味形成途径研究基础，发现葡萄糖氧化酶（GOD）对异味形成与释放具有显著的抑制作用，但关于GOD处理甜瓜汁后异味前体物质结构及其降解速率是否发生变化？产物与前体及异味组分之间是否发生相互作用？甜瓜汁中差异性组分是否与异味物质作用而影响其释放？等机理方面的系统研究还很缺乏。本项目利用高效液相色谱-四级杆飞行时间串联质谱和核磁共振等技术，明确GOD处理后甜瓜汁基质特性变化及其对异味前体结构影响；采用稳定同位素稀释分析、密度泛函理论等，阐明GOD酶解产物与异味前体及异味组分间相互作用；基于代谢组学和活性香气释放模型，从化学结构与传质阻力等方面，探讨酶处理前后基质差异组分对异味释放行为的影响，以期对GOD抑制热异味形成与释放的分子机制进行科学阐述。

Melons are typical representative of thermo-sensitive fruits. Cooked off-flavor which is a common odor attribute in thermal processing seriously affects the sensory quality of products. Based on our previous work about the identification of off-flavor and its precursors, off-flavor generation mechanism during thermal processing as well as inhibitors screening test, glucose oxidase (GOD) showed the best inhibition effect on cooked off-flavor. However, Systematic research of inhibition mechanism is still lacking, what is the change of structural characteristics of precursors? What is the intermolecular interaction mechanism among enzymatic hydrolysates, precursors and volatiles? and what is the effect on off-flavor release behavior? This project aims to (1) clarify the variation of matrix properties and precursors structures using HPLC-Q-TOF-MS and NMR and other techniques, (2) analyze the interaction between GOD enzymatic products and off-flavor and its precursors combined with SIDA and DFT techniques, and (3) evaluate the differences in melon juice components on off-flavor release behavior from the aspects of chemical structure and mass transfer resistance basing on the metabolomics and quantitative structural active aroma release model. To sum all, the present project will scientifically explain the molecular mechanism of the formation and release of cooked off-flavor inhibition in thermo-sensitive fruits by GOD.