【作者】 宋芸；

【导师】 崔政伟；

【作者基本信息】 江南大学 ， 机械设计及理论， 2008， 硕士

【摘要】 本课题研究了微波真空与真空冷冻组合干燥(先微波真空后冷冻干燥)代替纯冷冻干燥生产脱水蔬菜和水果,研究发现采用微波真空与真空冷冻组合干燥能够生产出优质的脱水果蔬,既能保持产品的色、香、味和营养,又能保持产品较好的外形和质构,同时能较大幅度地降低能耗。为了找到微波真空与真空冷冻干燥串联的最佳工艺参数组合,首先研究了微波真空干燥果蔬体积收缩的数学模型,针对不同果蔬品种提出相应的微波真空干燥工艺参数;通过响应面分析,得到微波真空干燥相关结论:功率密度一定时,水分损失与干燥时间成正相关关系,收缩系数与水分损失、功率密度成负相关关系,收缩系数与厚度近似成正相关关系。将微波真空干燥的最佳工艺参数与真空冷冻干燥工艺参数进行相关组合,然后通过正交试验得到胡萝卜片和苹果片的最佳组合干燥工艺参数:胡萝卜片,微波真空干燥阶段的真空度3.0—4.5 Kpa,微波功率密度0.82 W/g,胡萝卜片厚度8 mm,水分损失40%,收缩系数达到65%,冷冻干燥阶段加热板程序为,初始加热板温度设定为-15 oC,干燥12h,后升温至5 oC,干燥3 h,再升温至15 oC,干燥1 h,最后温升至30 oC至干燥终点。苹果片,微波真空干燥阶段的真空度3.0—4.5 Kpa,微波功率密度0.82 W/g,厚度8 mm,水分损失50%,收缩系数达到55%,冷冻干燥阶段加热板程序为,初始加热板温度设定为-12 oC,干燥11 h,后升温至0 oC,干燥3 h,再升温至15 oC,干燥1 h,最后温升至30 oC至干燥终点。对各种干燥方法进行产品质量和单位能耗及成本进行了分析和对比,得出微波真空与真空冷冻组合干燥生产的脱水果蔬产品质量接近纯真空冷冻干燥产品质量,与纯真空冷冻干燥相比,微波真空与真空冷冻组合干燥生产的脱水胡萝卜片能耗可降低56%,利润增加18%,脱水苹果片能耗可降低20%,利润增加10%。本课题研究表明:微波真空与真空冷冻干燥组合,可以生产出优质的脱水果蔬,产品质量能够比较接近纯真空冷冻干燥,且能耗和干燥成本降低。更多还原

【Abstract】 The combination of microwave vacuum drying (MVD) and freeze drying (FD) has been investigated to replace freeze drying alone in dehydration of fruits and vegetables. The study showed that this combined drying (CD) can produce high-quality end-products, which not only have original color and the nutrition, but also keep the desirable shape and the texture. Furthermore, the energy consumption of this combined drying method decreased greatly.In order to optimize the parameters of CD for dehydrated fruits and vegetables, the mathematical models of shrinkage are developed on the base of MVD experiments, and the technical parameters for drying fruits and vegetables are suggested. The MVD experiments showed that, at a fixed power density, water loss is proportional to the drying time, and the shrinkage coefficient is inversely proportional to the loss of water and power density, while it is proportional to the thickness of samples approximately.The parameters of MVD and FD are then matched and optimized, and the best parameters of CD are obtained by orthogonal experiments. The technical parameters for carrot is: vacuum pressure,3.0—4.5 K Pa;microwave power density , 0.82 W/g and the amount of water,dehydrated by MVD in advance about 40%. As a result, the shrinkage coefficient of carrot will be 65%. While during FD, the setting of heating plate procedure are: keeping the temperature at -15 o C for 12 h at first, then increasing to a temperature of 5 o C for 3 h, then at 15 o C for 1h ,finally keeping 30 o C till the end point of drying for carrots. The technical parameters for apple is: vacuum pressure,3.0—4.5 K Pa; microwave power density, 0.82 W/g; the loss of water by MVD, about 50%. The shrinkage coefficient of apple slices is about 55%. During FD, the setting of heating plate procedure are: keeping the temperature at -12 o C for 11 h, then increasing to a temperature of 0 o C for 3 h, then lasting 1h at 15 o C, finally keeping 30 o C till the end point of drying for apples.The quality、cost and the energy consumption of different drying methods are compared with FD, the quality of carrot and apple slices dehydrated by CD is near to that of FD, the cost of CD is reduced by 56% and its interest is increased by 18% in producing dehydrated carrot slices, and the cost of CD is reduced by 20% and its interest is increased by 10% in producing dehydrated apple slices.The combination of MVD and FD may be used as a alternative method to dehydrate fruits and vegetables in both good quality and low cost.更多还原