微波诱导低温压力强化萃取蓝莓中花青素的机理分析和过程控制

Rising extraction temperature caused by microwave volumetric heating mode may accelerate the extraction efficiency and result in the obvious degradation of anthocyanin in the microwave extraction system of blueberry. A scientific issue about the mechanism analysis and process control for the extraction improvement of antocyanin from blueberry by using microwave inducing pressure in low temperature would be studied to give the solutions in nature for problems of high anthocyanin degradation in the microwave extraction. The coupling effects of pressure and temperature on anthocyanin extraction would be analyzed to improve the inner pressure to remedy the limitation of low temperature resulting in the deficiency of diffusion driving force of anthocyanin within blue berry powder. The new extraction mode may ensure the extraction rate and decrease the degradation of anthocyanin. Dynamics models and heat-mass transfer equations describing the acquisition and degradation of anthocyanin extracted by microwave conditions would be developed to simulate the distributions and changes of temperature, pressure and anthocyanin concentration. The mechanism of microwave extraction would be revealed based on research results. Similitude criterions between microwave extraction conditions and processing parameters of heat-mass transfer equations would be derived to control the microwave extraction process with pressure in low temperature. On the basis of process analysis of heat-mass transfer, theory and technique of extraction mode of microwave inducing pressure in low temperature case would be studied deeply and systematically according to the research route of mode development-mechanism analysis-process control..This project overlaps and merges multi-disciplinary knowledge from Food Science and Technology, Agricultural Engineering, and Engineering Thermo physics, which develops a new mode of microwave extraction to improves the theory level of qulity control of microwave processing food.

在蓝莓微波萃取体系中，微波体加热方式引起温度快速升高，提高萃取效率的同时又引起花青素显著降解。为从本质上解决微波萃取时花青素降解的难题，提出微波诱导低温压力强化萃取蓝莓中花青素机理分析和过程控制的研究项目。本项目首先研究萃取体系内微波诱导压力与温度对花青素萃取的耦合效应，通过提高内部压力弥补低温下花青素在蓝莓内扩散动力不足，保证萃取速度，减少花青素降解；然后建立微波萃取时花青素获取和降解的动力学模型和传热传质方程，模拟温度、压力及花青素浓度的变化规律，揭示低温压力微波萃取模式机理；最后建立微波萃取条件与质热传递过程参数间的相似准则，实现对微波诱导低温压力萃取过程有效控制。以传热传质过程为线索，从模式提出—机理分析—过程控制方面系统深入研究低温压力微波萃取理论和工艺。.课题融合食品科学与技术、农业工程和工程热物理学科知识，建立微波萃取新模式，研究成果有助于提升微波加工食品品质控制理论水平。

在蓝莓微波萃取体系中，微波体加热方式引起温度快速升高，提高萃取效率的同时又引起花青素显著降解。为从本质上解决微波萃取时花青素降解的难题，提出微波诱导低温压力强化萃取蓝莓中花青素机理分析和过程控制的研究项目。. 研究萃取体系内微波诱导压力与温度对花青素萃取的耦合效应，微波功率导致萃取体系温度升高，促进花青素在蓝莓细胞内扩散速度和溶剂中溶解度，同时导致蓝莓细胞内应力升高到3.15 MPa，在细胞端面的中心出现破裂点，使得细胞内花青素迅速释放到溶剂中，而萃取体系温度达到50℃时，微波强度在100 W/g时内部压力增量最大，通过提高内部压力弥补低温下花青素在蓝莓内扩散动力不足，提高萃取速度。 建立微波萃取时花青素降解动力模型，确定微波诱导低温压力萃取特性，萃取动力学常数和降解动力学常数均随萃取温度升高而增大，而随料液比增加均呈现先增加后降低的趋势；萃取花青素的临界温度为50 ℃，在高于50 ℃花青素降解起主导作用，低于50 ℃花青素获取起主导作用。解析微波萃取体系内传热和传质规律，萃取体系内电场强度的分布不均，萃取容器中心处的微波能吸收量最大，萃取体系内整体温度升高，由中心向边缘呈降低趋势，形成“冷点”和“热点”现象，导致萃取动力不足和花青素降解，微波萃取参数的动态输入可提高温度分布均匀性。采用遗传算法优化出微波诱导压力促进花青素扩散的微波萃取参数的动态输入模式，第Ⅰ阶段微波功率870 W、转换点温度36 ℃、第Ⅱ阶段微波功率为400 W，花青素最高萃取率和最低降解率分别为85.19%和6.69%，优于常规微波萃取工艺，并建立该模式下相似准则模型，利用该模型可将萃取工艺推广到大型的微波萃取设备中；进行了蓝莓花青素分离纯化、结构鉴定及抗氧化活性研究。. 本项目揭示了微波辅助萃取蓝莓花青素传热传质、微波能吸收、压力破裂细胞壁的机理，解析了花青素萃取、纯化和抗氧化特性，优化得出高得率、低降解率的萃取工艺，研究结果可为高附加值浆果中活性成分的高效提取和纯化提供依据。