常见浆果的真空冷冻干燥特性研究

浆果不耐贮藏、易腐烂变质,需进行及时的采后处理。真空冷冻干燥技术可有效保存物料中的营养成分和感官特征,尤其适合高附加值水果的加工。试验以香蕉、葡萄、猕猴桃和蓝莓4种常见浆果为原料进行冻干加工,分别记录动态干燥过程,并对冻干产品特性进行分析。试验表明:香蕉、猕猴桃和蓝莓均能保持新鲜物料的形态,疏松多孔、质地酥脆,葡萄出现体积收缩、表面褶皱;香蕉、猕猴桃、蓝莓在升华干燥中出现了恒速干燥阶段,而葡萄无明显的恒速干燥阶段;冻干香蕉、猕猴桃和蓝莓3种浆果复水性分别为72.34%、76.23%和55.88%,维生素C保存率分别为88.47%、96.67%和78.11%,而葡萄复水性和维生素C仅为33.53%和22.67%。含糖量较高的浆果冻干效果不太理想,需继续进行干燥工艺研究。试验为浆果冻干提供了适宜性评价依据,在货架期延长、方便快捷运输等方面也具有一定的参考价值。

Vacuum Freeze-drying Characteristics of Common Berries

Berries are difficult to store and easy to rot. Therefore timely post-processing is required. Vacuum freeze drying technology can effectively maintain nutrition and sensory characteristics of fresh materials, especially for dehydration of high value-added fruits. Four common berries including banana, grape, kiwi fruit and blueberry were used as raw materials, and dehydrated by vacuum freeze drying. Results showed that banana, kiwi fruit and blueberry maintained the original status of fresh materials and the products were porous and crispy. However, shrinkage and distortion were occurred in freeze-dried grapes. Constant speed drying stages were appeared during vacuum freeze drying of berries except grape. Rehydration rates of banana, grape, kiwi fruit and blueberry were 72.34%, 76.23% and 55.88% respectively, and their preserving rates of vitamin C were 88.47%, 96.67%, and 78.11%, respectively. The rehydration rate and the preservation rate of grape were only 33.53% and 22.67%, respectively. Suitability evaluation of vacuum freeze drying for common berries is provided in the experiment, and it has a certain reference value in helf life extension and convenient transportation of berries.