猕猴桃热风干燥与冷冻干燥的实验研究

Study on Freeze-drying and Hot-air Drying Kiwi-fruit Slice

本研究对真空冷冻干燥和热风干燥猕猴桃切片进行了对比实验,比较了不同冷冻干燥工艺和热风干燥工艺下猕猴桃VC损失率和干燥速率。实验发现热风干燥实验中,厚度、温度和对流情况三个因素对干燥速率和VC损失率两个指标都有显著影响(p<0.01)。最佳猕猴桃热风干燥工艺条件是:猕猴桃切片厚度取中间值6mm,温度取高值70℃,对流情况取加风。冷冻干燥实验中,厚度、一次干燥温度对干燥速率有显著影响(p<0.05),冻结速率无显著影响。厚度、一次干燥温度和降温速率对VC损失率有显著影响(p<0.05)。最佳猕猴桃真空冷冻干燥工艺条件是:猕猴桃切片厚度取中间值8mm,一次干燥温度-10℃,冻结降温速率取快速冻结。热风干燥的平均干燥速率远远大于冻干实验结果。冷冻干燥的VC损失率大大小于热风干燥过程。

In this paper the hot-air drying and freeze drying of kiwi-fruit slices are comparatively studied. The VC loss ratio and drying rate are taken as criterion. In hot-wind drying experiment, drying rate and VC loss ratio are significantly influenced by thickness of sample, temperature of process and convectional condition（p 〈 0.01）. In freeze drying experiment, the thickness of sample and the primary drying temperature influence both the drying rate and VC loss ratio, and the VC loss also influences by freezing rate（p 〈 0.05）. The ideal processing parameter are 6 mm thick, 70℃ temperature and enhanced the convection in hot-air drying process, and 8 mm thick, - 1O℃ primary drying temperature and quick freezing in freeze drying. The drying rate in freeze drying is less than in hot-wind drying but the VC loss ration in freeze drying is better than in hot-wind drying.