电磁场影响果蔬水预冷过程热质传递特性与病原菌活性的机理研究

Rapid hydrocooling for postharvest fruit and vegetable is an important method to reduce nutrient consumption and inhibit the proliferation of pathogens. The high energy consumption of the hydrocooling unit and the cross infection of pathogens in cooling water are difficult problems that needs to be solved. This project based on the thermophysical theory and electromagnetic biological effect, taking the high-value and perishable sweet cherry as the object, carries out theoretical analysis and experimental research on the effect of low-temperature and electromagnetic field treatment on key parameters related to heat and mass transfer during hydrocooling of the sweet cherry. Furthermore, the mathematical model of heat and mass transfer during hydrocooling with electromagnetic effect will be constructed. The muti-physics coupling effect mechanism of the heat and mass transfer will be explored combining analysis of tissue’s microstructure and electromagnetic micromechanical. Meanwhile, the experimental study of coupling effect combining electromagnetic field and low temperature field on the Listeria will be carried out. And then on basis of the corrected Arrhenius equation including the low-temperature and magnetic parameters, the dynamic prediction model of the proliferation rate will be constructed. Furthermore, coupling effect mechanism of low-temperature and electromagnetic field on the enhanced sterilization will be explored by microstructure analysis. Finally, Factors of enhanced heat transfer, bactericidal action and quality index are comprehensively analyzed using the Response Surface Method. And a multi-objective comprehensive quantitative evaluation mathematical model will be established to optimize processing parameters. The research can provide basic data support and scientific basis for the development and application of the hydrocooling technology with low-temperature and electromagnetic field treatment on fruit and vegetable.

采后果蔬快速水预冷是降低营养物质消耗、抑制病原菌增殖的重要保鲜方法。水预冷机组的高能耗和冷却水病原菌交叉感染是当前亟待解决的难点问题。本项目拟以高值易腐特性果品-甜樱桃为研究对象，基于生物热物理理论及电磁生物效应，开展低温温度场与电磁场耦合作用影响樱桃关键物性参数的理论分析及实验研究，进而建立水预冷过程传热传质数学模型，结合组织微观结构分析及电磁微观力学理论，探索多场耦合作用影响热质传递的机制。开展低温温度场联合电磁场耦合作用影响李斯特菌活性实验研究，基于低温与电磁参数修正的Arrhenius方程，构建菌落增殖速率动态响应预测模型，结合显微结构分析探索低温电磁耦合作用强化抑菌杀菌机理。采用响应曲面法，综合分析强化传热、杀菌效果及抑制品质衰变等因素，建立多目标综合量化评价数学模型实现低温电磁作用参数的优化。本项目拟开展的研究可为果蔬低温电磁水预冷技术的发展及应用提供基础数据支撑和科学依据。

随着近年来生物研究和工程技术的发展，人们发现磁场处理后能够有效预防果蔬腐败，延长果蔬货架期，在果蔬保鲜领域展现出广阔的应用前景。本项目以樱桃为试验对象，基于磁场生物学及磁场强化换热研究，总结磁场强度与导热系数、比热等参数间数值关系，利用COMSOL软件构建磁场水预冷传热模型，搭建磁场水预冷樱桃试验系统。研究表明：樱桃的导热系数随磁场强度（0-100Gs）的增加而增加，比热呈现非线性多极值变化；适宜强度的磁场作用能够有效提高水预冷换热速率，缩短预冷时间，揭示了磁场作用可以影响食品的导热系数等物性参数，从而影响其换热效率的机制。通过实验探究磁场协同水预冷处理对樱桃贮藏期内保鲜品质的影响发现：磁场耦合处理对维持贮藏期樱桃品质有积极的作用。40Gs磁场处理组对樱桃保鲜效果最佳；其失重率低于无处理组34.5%，整个贮藏期间硬度仅减小5.07%，色差仅增加8.24%，可溶性固形物波动为1.97%。磁场通过影响樱桃理化指标及感官品质，以起到保鲜的效果。其次，开展了低温度场与静磁场联合作用影响樱桃表面菌落增殖的试验研究，根据菌落生长速率方程与Logistics方程进行拟合计算菌落增殖速率与迟滞期。结果显示，在4℃贮藏过程中适宜的磁场辅助处理对于樱桃中的菌落繁殖过程有显著抑制作用。40Gs组效果最佳，其樱桃总菌落的平均生长速率相比于常温对照组降低39%，相比于同等未加磁场低温对照组降低23.72%，最大比生长速率明显小于各对照组，而迟滞时间长于各对照组，其原因可能与磁场作用影响了菌落基因转录过程相关酶活性有关。最后，构建了磁场水预冷的熵权法与层次分析法（AHP-EWM）联合评价模型。对樱桃品质指标进行综合权重分布评分分析，发现40Gs磁场水预冷处理对樱桃的保鲜效果最好。评价结果与实验结果一致性较好。因此，磁场作为一种新兴物理场技术能够增强果蔬水预冷效率，进一步提高贮藏期果蔬保鲜品质，同时抑制菌落的繁殖速度，从而达到保鲜的目的。本项目的研究结果，可为预冷技术的发展提供理论及试验参考。