不同干燥方式对红枣品质特性的影响

Effect of Drying Treatment Methods on the Quality Properties of Red Jujube

通过对不同干燥方式所得产品的硬度、色泽和营养成分的含量进行测定分析,并对其进行电镜扫描观察,研究不同干燥方式对红枣品质特性的影响。结果发现:硬度大小依次为微波干燥>热风干燥>真空干燥>变温压差膨化干燥>冷冻干燥;色泽无明显差异。营养成分中,总糖、还原糖、粗纤维、蛋白质和总黄酮含量均增加;冷冻干燥产品总酸和钾含量减少,其余干燥方式则增加;真空干燥和变温压差膨化干燥产品的维生素C含量增加,其余减少;热风干燥产品磷含量减少。组织细胞结构中:热风干燥产品严重收缩,结构紧密;微波干燥与真空干燥产品密度较大;冷冻干燥产品孔隙较大较均匀一致,呈现出较好的蜂窝状结构;变温压差膨化干燥产品细胞呈多孔海绵状,组织结构疏松,具有均匀的多孔结构。综合来看,变温压差膨化干燥产品硬度较低,营养保存好,口感酥脆且生产成本也较低,适宜在枣加工业进行推广。

The hardness, color and nutritional content of the dried red jujube samples were measured and analyzed, and its scanning electron microscope was observed for investigating the effects of drying methods on quality characteristics of red dates. The results showed that the order of hardness was microwave drying 〉 hot air drying 〉 vacuum drying 〉 explosion puffing drying 〉 freeze drying and no significant difference was found in color. Nutrients, the total sugar, reducing sugar, crude fiber, protein and total flavonoid content were increased; the total acid and potassium of the products were reduced by freeze-dry, but increased by treatment with other drying methods; vitamin C content of the products were increased by vacuum drying and the explosion puffing drying but reduced by other methods; phosphorus content of the product by hot air drying products was reduced. Cell structure of the hot-air drying products contracted. The density of the products by microwave drying and vacuum drying was improved and the products by freeze-dry showed a large and uniform porosity and a better cellular structure. The explosion puffing drying led to extruded porous sponge-like cells and loose organizational structure, with a uniform porous structure. In summary, the products by low pressure extruded dry showed high hardness and nutrition, showing crisp and the taste with low cost of production, which was suitable for the processing industry to promote the jujube.