【作者】 尹海蛟；

【导师】 杨昭；

【作者基本信息】 天津大学 ， 制冷及低温工程， 2012， 博士

【摘要】 我国是一个农业大国,近年来果蔬产量均位居世界首位,然而由于完整独立的果蔬冷链系统尚未形成,导致我国果蔬采后损失严重,每年造成的直接经济损失高达千亿元。此外,随着大众对健康及食品安全问题的关注,化学保鲜方法备受质疑,探索绿色环保型物理保鲜方法已成为果蔬保鲜技术领域的重要课题。本文以多个学科的理论方法为研究基础,采用理论与试验相结合的研究方法对果蔬恒温恒湿保鲜系统关键技术及采后温度激化处理工艺进行了系统研究,全文内容概括如下:(1)对采后果蔬恒温恒湿保鲜冷库系统的智能控制、除霜方法及库内气流组织等关键性技术进行了研究。首次提出了复合加热式新型冷库除霜方法,搭建了除霜系统的硬件结构,对新型除霜方法的技术特性进行了试验测试;采用CFD数值模拟方法对影响保鲜冷库系统流场分布及气流组织的关键部件及结构进行了探讨。(2)建立了柱状与球状果蔬温度激化处理的普适传热模型,采用Taylor级数展开式有限差分法对果蔬的传热过程进行了数值计算;试验验证结果表明所建传热模型能够准确预测多种边界条件下不同形状果蔬的组织温度变化;对比研究了不同激化处理方式中果蔬的传热规律及动态响应特征;考察了果蔬大小、包装方式、处理介质流速、温度及相对湿度等参数对激化处理传热效果及组织失重率的影响。(3)以黄瓜为试材,采用传热机理分析与生物指标测试相结合的方法,对不同强度冷激与热激处理黄瓜的贮藏品质进行了对比研究,并提出了果蔬保鲜效果的熵权模糊综合评判方法。(4)以色差、色调角、表面亮度、硬度、腐烂指数及失重率为优化响应值,对黄瓜热激处理工艺进行了响应曲面法(RSM)优化研究,试验方案采用中心旋转组合法设计(CCD),获得了各品质指标的二次响应曲面模型;采用线性权和法构建了优化过程的评价函数,并通过主成分分析法确定了评价函数指标集的权重向量。(5)介绍了果蔬颜色的物理检测方法,通过试验筛选出了黄瓜鲜度的最佳颜色评价指标;对冷藏、热激+冷藏、冷激+冷藏、自发气调+冷藏4组黄瓜颜色指标的衰变规律进行了化学反应动力学研究,确定了各处理组黄瓜亮度与色差动力学模型的反应级数、反应速率常数及表观活化能。本文所得相关结论可为果蔬采后保鲜方法的选择及处理参数的确定提供参考,同时对恒温恒湿保鲜冷库系统的优化运行具有现实意义。更多还原

【Abstract】 China, as a primary agricultural country, the yields of fruits and vegetables have ranked the first throughout the world in recent years, however, because of the morbid cold chain, postharvest losses of fruits and vegetables are serious, and the direct economic loss reaches one hundred billion yuan every year. In addition, with the issues related human health and food safety being concerned, chemical preservative method is fully questionable, and thus green environmental protected physical method exploration for fruits and vegetables postharvest preservation has become important task. Based on multi-subject approaches, cold storage and pre-storage temperature shock treatment for fruits and vegetables were theoretically and experimentally researched in present dissertation, and the main contents are as following:(1) The intelligent control, defrosting method and airflow organization of cold storage for fruits and vegetables preservation were studied. A novel cold storage defrosting method was proposed for the first time, and its technical characteristics were experimentally researched. With the CFD numerical simulation method, the key components affecting cold storage airflow distribution were analyzed. (2) The universal heat transfer model for columnar and spherical fruits and vegetables was established and numerical calculated with Taylor series expansion finite difference method. The results showed that the established models could accurately predict the temperature changes of fruits and vegetables in different shapes. Heat transfer characteristics of products subjected to different temperature shock treatment were compared and studied. The effects of fruit size, packing, medium velocity, treatment temperature and relative humidity on heat transfer and tissue weight loss were investigated. (3) With cucumber as test materials, the effects of cucumbers preservation subjected to different strength of cold and heat shock treatment were comparatively studied by method of heat transfer analysis combined with physicochemical indexes testing, and entropy weight of fuzzy comprehensive evaluation method for fruits and vegetables fresh-keeping effect evaluation was proposed. (4) Taking total color difference, hue angle, lightness, firmness, rot index of fruit as response parameters, heat shock treatment technique for cucumber was optimized with response surface methodology (RSM). The optimizing experiment scheme was central composite designed, and the quadratic models for quality parameters of cucumber were obtained. Furthermore, evaluation function for optimization was established through liner weighting method, in which the weight vector was determined by principal component analysis method. (5) The physical method for fruits and vegetables color measurement was introduced, and the best indexes for cucumber color evaluation were experimentally determined. Color of cucumber subjected to refrigerating, heat shock treatment + refrigerating, cold shock treatment + refrigerating, modified atmosphere package + refrigerating respectively were chemical kinetics studied, and the reaction orders, reaction rate constants and apparent activation energies of cucumber lightness and total color difference were obtained. The conclusions obtained can provide references for preservation method selection and treatment parameter determination of postharvest fruits and vegetables, meanwhile, it also has an important significance for cold storage system optimization.更多还原