苹果干制中多酚-果胶相互作用对制品贮藏中多酚氧化特性影响机制研究

The state of polyphenols in dried fruits and vegetables and their interaction with pectin not only determine their biological activity, but also are the key factors affecting the quality of dried fruit and vegetable products. The mechanism of polyphenol-pectin interaction formation caused by water migration in the fruits and vegetables drying process is still unclear. This project focused on investigating the interaction of polyphenols and pectin caused by moisture migration in precise hot air drying, and the effect of different polyphenol-pectin interaction on the polyphenol oxidation on the basis of apple cube model system. The composition and distribution of polyphenols were analyzed by DESI mass spectrometry in situ imaging technology; the structural characteristics of pectin were analyzed by gel chromatography and infrared spectroscopy; the distribution and location of polyphenols in cells were identified by confocal laser scanning microscopy (CLSM); the formation of interaction force between polyphenols and pectin was analyzed by isothermal titration microcalorimetry (ITC); the structure of polyphenols oxidation products was characterized and identified by high resolution mass spectrometry (UPLC-QEF-MSn). Furthermore, the solid-state simulation system, polyphenol-pectin binary system and model oxides of main polyphenols were constructed. To clarified the mechanism of polyphenol-pectin interaction formed in hot air drying process effect on the oxidation characteristics of polyphenols. This study aims to provide theoretical basis for controlling, regulating and improving the quality of dried fruits and vegetables.

干制果蔬中多酚的存在状态及其与果胶的相互作用不但决定其生物活性，而且是影响果蔬制品品质的关键因素。果蔬干制中水分迁移引起多酚-果胶相互作用的形成对制品贮藏中多酚氧化特性的影响机制还不明确。据此，本项目以苹果丁为模式体系，研究精准热风干制水分迁移引起的多酚与果胶相互作用的差异，并分析干制苹果丁贮藏中多酚与果胶相互作用变化对多酚氧化特性的影响。采用DESI质谱原位成像技术分析多酚组成和分布；凝胶色谱、红外光谱法分析果胶的结构特征；激光共聚焦扫描电镜（CLSM）明确多酚在组织细胞中的分布定位；等温滴定微量热法(ITC)分析多酚与果胶相互作用的形成；高分辨质谱（UPLC-QEF-MSn）表征并鉴定多酚的氧化产物结构。构建固态模拟体系，多酚-果胶二元体系，以主要多酚的模型氧化物，解析精准热风干制处理引起的多酚-果胶相互作用的形成对多酚氧化特性的影响机制，为提高干制果蔬品质提供理论依据。

项目背景：褐变严重影响干制水果感官、营养、加工等品质，主要与干制加工中褐变反应有关。目前，干制水果中多酚的存在状态及其与果胶的相互作用不但决定其生物活性，而且是影响果蔬制品品质的关键因素。水果干制中水分迁移引起多酚-果胶相互作用的形成对制品贮藏中多酚氧化特性的影响机制，及果胶大分子物质改变对体系褐变的影响还还不明确。.主要研究内容：研究干制苹果丁水分迁移速率对多酚-果胶互作形成的影响，解析干制苹果丁中多酚-果胶交互作用方式在贮藏过程中的变化；明确干制苹果丁贮藏过程中多酚-果胶互作对多酚氧化的影响机制。.重要结果，关键数据：不同水分迁移速率干制的苹果丁褐变相关荧光物质分布存在差异。高水分迁移速率干制苹果丁褐变相关荧光物质分布分散，改变制品最终呈色。水分迁移速率与干制苹果丁表观亮度和红度分别呈显著负相关和正相关（p<0.01）。苹果丁表观褐变与多酚氧化、美拉德反应以及果胶演变的关联研究表明，相比低速水分迁移，高速水分迁移干制苹果丁的表观褐变增加了8.52%，这与游离 5-HMF和绿原酸含量增加有关，且与果胶分子结构特性（GalA、DE、Mw、PDI、Ratio1、Ratio2、Ratio3、Rg和Rc）的变化显著相关。苹果丁贮藏阶段褐变程度的改变与5-HMF的增加、绿原酸的减少以及果胶结构特性显著相关。果胶通过空间位阻和离子屏蔽作用分别对儿茶素和绿原酸酶促氧化速率产生抑制和促进作用。果胶和多酚通过多酚的芳香环和果胶的甲氧基、羟基等发生相互作用，影响多酚酶促反应速率和游离多酚含量，影响体系褐变。此外，果胶在热处理和贮藏阶段发生解聚，分子量减小、甲酯化度降低、支链和直链程度降低以及微观构象改变，并且产生引起体系褐变的不饱脲苷等产物。果胶解聚产物会与赖氨酸发生美拉德反应，增加反应产物5-HMF和类黑精含量，提高体系褐变水平。.科学意义：提高干制水果色泽品质提供一定的理论基础和技术支持。