射频加热对低水分食品中致病菌的杀灭机理及方法研究

In the processing and marketing channels of low-moisture foods, the food-borne pathogens may survive in low water activity environment but grow rapidly as soon as the environment changes, resulting in many potential food safety outbreaks and accidents. With concerns of consumers on food safety and environmental pollutions caused by chemical fumigations, and increased international regulations to limit the use of fumigants, it is extremely urgent to study novel and environmentally-friendly physical alternatives for control of pathogens. Radio frequency (RF) treatment has been identified as one novel and physical heating method, providing significant advantages and potential application prospects in low-moisture food pasteurizations. In the proposed project, we will select representative low-moisture foods with different structure and composition and measure their thermal and dielectric properties as a function of frequency, moisture content, and temperature to determine the penetration depth, heating uniformity and differential heating in foods; establish thermal death kinetic models of target pathogens under different moisture contents and heating rates to explore the mechanism of controlling pathogens using RF energy; improve heating uniformity and optimize RF treatment parameters using finite element simulation methods to ensure pathogen controls and achieve marketable quality characteristics of RF treated low-moisture foods. This project mainly combines unique research capacities in three interdisciplinary research directions of food microbiology, food chemistry and food engineering to develop safe and effective RF heating methods for pathogen inactivation in low-moisture foods. The project will provide reliable mechanisms and new technology for low-moisture food industry, and lay a foundation to establish effective pasteurization methods in other low-moisture foods.

在低水分食品的流通环境中食源性致病菌可长期存活，一旦外界条件发生变化就能迅速繁殖，产生许多潜在的食品安全问题，因此探索安全可靠的非化学灭菌方法显得尤为迫切。射频技术作为一种新型物理加热方法，在低水分食品灭菌中具有显著优势和潜在应用前景。本项目选取具有代表性的不同结构与成分的低水分食品，进行射频加热对致病菌的影响及杀灭机理研究，分析所选物料在不同水分与温度条件下的热与介电特性，探明射频波在所选物料中的穿透性、均匀性和选择性加热机理；构建不同水分活度和加热速率下所选物料中致病菌的热杀灭动力学模型，明确致病菌的射频热杀灭规律；利用有限元计算机模拟改善加热均匀性，优化调控参数，提高灭菌有效性并减少品质损失。本项目将通过食品微生物、食品化学和食品工程三大学科的交叉融合，建立安全有效的食品射频灭菌方法，为保障我国低水分食品的食用安全提供可靠的理论与技术支持，并为其它低水分食品灭菌方法的建立奠定基础。

在低水分食品的流通环境中食源性致病菌可长期存活，一旦外界条件发生变化就能迅速繁殖，产生许多潜在的食品安全问题，因此探索安全可靠的非化学灭菌方法显得尤为迫切。射频技术作为一种新型物理加热方法，在低水分食品灭菌中具有显著优势和潜在应用前景。本项目选取具有代表性的不同结构与成分的低水分食品，开展了射频加热对致病菌的影响及杀灭机理研究，分析了所选物料在不同水分与温度条件下的热与介电特性，探明了射频波在所选物料中的穿透性、均匀性和选择性加热机理；构建了不同水分活度和加热速率下所选物料中致病菌的热杀灭动力学模型，明确了致病菌的射频热杀灭规律；利用有限元计算机模拟改善加热均匀性，优化调控参数，提高灭菌有效性并减少品质损失。结果表明，射频加热比传统加热快、均匀性好与效益高等，相比微波、红外等新型加热技术穿透深度大，更加适于开展大宗农产品物料的工业化热处理；利用温度调节方便、控制精确可靠和试验重现性好的加热板系统，确定了粪肠球菌为最耐热的菌种以及Weibull分布模型为较优的热致死动力学模型。通过检测巴旦木、花生、核桃、小麦、面粉等低水分农产品随频率、温度、水分含量变化的介电常数和损耗因子，计算了射频在食品中的穿透深度；通过有限元模拟射频加热中辅以热风、传送带运动和振动搅拌等措施，研发了螺旋与机械转动系统，优化了射频加热调控参数，提高了射频加热均匀性；微生物的耐热性随着水分活度与加热速率的增加而降低。通过扫描电镜图与转录组分析阐明了水分活度以及加热速率对致病菌耐热性影响的机理。本项目通过食品微生物、食品化学和食品工程三大学科的交叉融合，建立了安全有效的食品射频灭菌方法，为保障我国低水分食品的食用安全提供了可靠的理论与技术支持，并为其它低水分食品灭菌方法的建立奠定了理论基础。

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