NFC桃汁品质接近新鲜水果，是促进丽江雪桃产业发展的重要加工产品。但NFC果汁加工中易发生多酚氧化酶(PPO)引起的酶促褐变，使品质降低。果蔬中普遍存在游离态(sPPO)和膜结合态(mPPO)两种PPO，mPPO不易被钝化，会在贮藏期引发褐变。高压均质(HPH)是一种可实现连续加工的非热加工方式，能有效抑制褐变，但对果汁和粗酶液中PPO钝化效果差异显著。本项目以雪桃为原料，采用HPH作为加工手段，分析HPH对NFC桃汁中mPPO和sPPO活性和结构的影响，重点研究HPH处理后mPPO的释放和钝化；明确sPPO和mPPO主要内源性酚类底物和对应褐变产物，建立HPH处理后酚类底物和褐变产物相关性;基于PPO-果胶模拟体系，探讨PPO和果胶的相互作用机制，研究HPH处理后果胶变化对PPO活性和结构的影响。最终阐明HPH对sPPO和mPPO活性和结构的作用，揭示HPH抑制NFC桃汁酶促褐变机制。

As the consumers are demanding more safe and nutritious food products, NFC juice (Non From concentrate) is gaining popularity due to its closer to the taste, flavor and nutrition of fresh fruit. NFC peach juice should be an important product to promote the development of peach industry in Lijiang, Yunnan. Enzymatic browning is mainly attributed to the action of polyphenol oxidase (PPO), which contributes to oxidization of phenolic compounds in the presence of molecular oxygen. Enzymatic browning decreased the commercial quality, organoleptic acceptance and nutritional value of the product. Generally, there are two forms of PPOs existed in plant, including soluble PPO (sPPO) and membrane-bound PPO (mPPO). While mPPO is either weakly or strongly bound to the thylakoid membrane and it shows more stability towards processing. Thus mPPO is a potential detrimental factor for browning in juice during storage. High pressure homogenization (HPH) is a non-thermal technology achieving continuous processing for liquid food, which can inhibit the Maillard reaction and enzymatic browning in the juice. Previous studies showed that the inactivation effects of PPO in juice and buffer were significant different by HPH. In this study, mechanism of HPH on enzymatic browning and changes of related factors in NFC peach juice will be investigated. Effects of HPH on the activity and structure of mPPO and sPPO will be analyzed, especially the release and inactivation of mPPO in NFC peach juice after HPH; The changes of phenolic substrate and browning product in NFC peach juice after HPH also will be analyzed; The PPO-pectin simulation system will be built to explore the interaction between PPO and pectin, and the effect of pectin on activity and structure of sPPO and mPPO will be analyzed. The present study will reveal the effect of HPH on PPO activity and structure, and the inhibition mechanism of enzymatic browning in NFC peach juice after HPH, and provide the basis for application of non-thermal technology in NFC juice industry, which have important theoretical and practical significance.