本文研究了真空冷冻干燥过程中鲜食枣营养品质及抗氧化活性的变化规律，为实际生产加工产品选择合适的干燥时间提供理论依据。结果表明：冷冻干燥过程中，鲜食枣还原糖含量存在显著性差异，且干燥结束时显著升高（p<0.05）；冻干产品维生素C保留率高达99.58%；有机酸是产品中重要的风味营养物质，其中，草酸、柠檬酸含量在冻干过程中均存在显著性差异（p<0.05），且在干燥结束时，草酸、酒石酸、柠檬酸含量分别是鲜样的1.64倍、1.32倍、3.83倍；冻干过程鲜食枣ABTS+?清除能力、抗氧化力均存在显著性差异（p<0.05），且冻干后ABTS+?清除能力提高6.91%，抗氧化力保留率达92.01%。由此可见，冻干过程中冻干时间对营养物质含量及活性有重要影响。冻干6~9 h有利于保持贮藏的水分和较高的营养品质，同时有助于降低能耗，并保持其功能价值。

Variations in nutritional properties and antioxidant activity of jujube fruits during different stages of vacuum freeze-drying were investigated to provide a scientific basis for selecting the appropriate drying time during production and processing. The results showed that during freeze-drying of the jujube fruits reducing sugar content increased significantly by the end of drying (p<0.05). The titratable acid content of freeze-dried jujube fruits was 0.92 times as much as fresh jujube fruits, which is one of the reasons for the drop in the sugar:acid ratio observed in freeze-dried products. Additionally, freeze-drying produced a higher retention rate of vitamin C (99.58%) over time, as compared to its fresh counterpart. The organic acid content of fruits is an important factor in determining flavor, and this study found that the freeze-dried jujube fruit oxalic acid, tartaric acid, and citric acid content were 1.64 times, 1.32 times, and 3.83 times as much as the fresh fruit, respectively. During freeze-drying, jujube fruits appeared to increase their ABTS+? scavenging power and antioxidant capacity (p<0.05), with the former increasing by 6.91% and antioxidant capacity increasing by 92.01%. Therefore, freeze-drying time has a significant effect on the nutrient content and antioxidant activity of the fruits being processed. The freeze-drying time ranging from 6 to 9 is beneficial in reserving moisture, and maintaining nutritional and functional property.

陕西省科技统筹创新工程计划项目（2013KTZB02-03-04）；榆林市科技局项目（2012cxy3-7）