高压均质对NFC芒果汁流变特性的影响及机制研究

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. Thermal treatment is the most common and least expensive technology to protect NFC juice from spoilage. However, Thermal energy inevitably leads to the destruction of NFC juice quality, especially the change of rheological property, inducing the loss of cloud stability. Since rheological property of NFC juice is important for the design of unit operations, process optimization and high quality product assurance. As is a novel non-thermal technology for pasteurization, High pressure homogenization (HPH) can effectively solve the contradiction between overheating (reducing the food's organoleptic properties) and underheating (leading to unsafe and low-quality food products). HPH is based on the same principle as conventional homogenization but which works at significantly higher pressures (up to 400 MPa), and it is being investigated to effectively decrease microbial activity in food products. However, there are only a few works in the literature regarding the quality changes in fruit juice due to HPH, especially regarding their rheological property. The present study is to analyze factors including particle properties, pectin and endogenous enzyme in NFC juice, contributing to the formation of rheological property, to reveal the formation mechanism of rheologiclal property of NFC mango juice during HPH processing. This study provides the basis for application of non-thermal technology in NFC juice industry, has important theoretical and practical significance.

NFC果汁具有口感、风味和营养更接近新鲜水果的特点，是国际果汁市场的重要发展方向。但NFC果汁为热敏性产品，采用热杀菌技术会导致产品品质尤其是流变特性的破坏，造成产品稳定性降低出现澄清现象，严重影响产品品质。本项目以NFC芒果汁为对象，采用非热加工技术中的高压均质技术（HPH）取代热杀菌技术，以解决食品安全和品质破坏之间的矛盾；采用稳态模式和动态模式分析HPH对NFC芒果汁流变特性的影响，明确其流变特性及其变化；开展HPH对果胶甲基酯酶（PME）和半乳糖醛酸酶（PG）钝化动力学的研究，解析HPH钝酶效应在流变特性变化中的作用；开展HPH对果汁颗粒、果胶等的影响研究，解析HPH均质效应在流变特性变化中的作用。本研究旨在揭示HPH对NFC芒果汁流变特性的影响及机制，为非热技术在NFC果汁的应用提供依据，具有重要的理论价值和实际意义。

本项目以NFC芒果汁为对象，采用非热加工技术高压均质技术（HPH）取代热杀菌技术，研究了HPH对微生物和品质的影响，分析了HPH对流变特性的影响及机理，以解决食品安全和品质破坏之间的矛盾。HPH能有效杀灭NFC芒果汁中的菌落总数、霉菌、酵母和接种的大肠杆菌，提高压力、处理温度和均质次数可使菌落总数、霉菌和酵母分别降至2.0 log CFU/mL和20 CFU/mL以下。4℃贮藏60天期间，HPH芒果汁中菌落总数没有显著变化，保持在安全限以下，霉菌和酵母未检出。HPH处理对NFC芒果汁中接种大肠杆菌的杀菌效果可用简化的Weibull模型拟合。HPH处理和贮藏期间NFC芒果汁的pH、TSS和TA没有显著变化，总色差△E＜2。HPH处理显著提高了NFC芒果汁中类胡萝卜素和多酚的含量，并增强其抗氧化能力，贮藏期间维生素C、类胡萝卜素、多酚含量及抗氧化能力保持较好。在此基础上，研究发现HPH处理可提高NFC芒果汁的混浊稳定性。HPH处理后NFC芒果汁颗粒粒径减小，混浊度升高。且随着压力、进料温度和均质次数的升高，果汁颗粒粒径分布峰向左移动，小粒径颗粒增多。NFC芒果汁呈现剪切变稀的流变特性，且表现出一定的触变性和弱凝胶特性。HPH处理显著提高了NFC芒果汁的表观黏度、触变环相对面积、贮藏模量G′和损耗模量G′′。HPH处理后NFC芒果汁中水溶性果胶含量显著提高，有利于提高果汁稳定性。另外，初步研究了HPH对果胶溶液性质的影响，发现HPH可降低果胶溶液的粘度，而对其基本结构没有影响。