甜樱桃非恒温冷链流通中基于果胶HG结构演化的软化机理研究

低温冷链是采后甜樱桃流通的重要方式，然而不可避免的温度波动会使甜樱桃的品质尤其是质地发生劣变。因此，本项目以非恒温冷链温度模式下的甜樱桃为研究对象，建立甜樱桃质地特性变化的动力学模型；运用Real-time FQ PCR对甜樱桃果胶酯酶（PME）和内切多聚半乳糖醛酸酶（endo-PG）基因表达水平进行研究，揭示温度变化调控PME和endo-PG活性变化的机制；借助IR、HPLC、NMR、AFM等分析手段探索细胞壁果胶同聚半乳糖醛酸（HG）分子结构的演化途径，结合PME与endo-PG活性及其基因表达的变化规律，建立甜樱桃PME与endo-PG水解细胞壁果胶HG的降解模型；同时与甜樱桃质地特性变化的动力学模型相关联，阐明甜樱桃在非恒温冷链温度模式下基于果胶HG结构演化的软化机理。项目研究将进一步丰富甜樱桃的质地软化机理，并为采后甜樱桃冷链流通过程中品质控制提供理论依据。

Low temperature cold chain is an important circulation method of postharvest sweet cherry. However, the temperature fluctuation which inevitably occurs in circulation results into poor quality of sweet cherry. In this research, sweet cherry under non-isothermal cold chain is the study material. Firstly, the kinetic model of firmness will be established. Moreover, the expression level of pectinmethylesterase (PME) and endo-polygalacturonase (endo-PG) gene will be investigated by real-time fluorescent quantitative PCR (Real-time FQ PCR) to clear whether the increasing enzymatic activity is induced by temperature fluctuation. Then, structure degradation of pectin homogalacturonan (HG) will be studied by infrared spectrum (IR), high performance liquid chromatography (HPLC), Nuclear Magnetic Resonance (NMR) and atomic force microscope (AFM). On this basis, the degradation model of pectin HG by PME and endo-PG will be build. Finally, the above studies together with kinetic model of firmness could illuminate the degradation mechanism of pectin HG structure during sweet cherry softening under non-isothermal cold chain condition. Conclusion of this research will further enrich the softening mechanism of postharvest sweet cherry, and provide a theoretical basis on the quality control of postharvest sweet cherry during cold chain circulation.