谷朊粉对冻干枣粉抑制吸湿作用研究

目的 研究谷朊粉对冻干枣粉吸湿特性的影响。方法 将谷朊粉与枣浆按不同比例均匀混合，真空冷冻干燥后粉粹，过60目筛制备不同配比的冻干枣粉。结果 谷朊粉显著降低了冻干枣粉的平衡含水率(equilibrium moisture content，EMC)。吸湿等温结果表明，红枣与谷朊粉质量比10:0、7:3、1:1、3:7样品的吸湿等温类型属“J”型增长，而0:10样品的属“S”型增长，表明谷朊粉的添加并未改变冻干枣粉吸湿等温类型；接触角随着谷朊粉的添加量的增大而增大，其值从31.22°增大到76.7°，说明谷朊粉可以减弱冻干枣粉的表面润湿性。从宏观和扫描电镜图中可知，冻干枣粉结块现象随着谷朊粉的添加量的增大而逐渐减轻。低场核磁结果显示，谷朊粉降低自由水的含量，减少水分向高自由度方向的迁移程度。结论 一定量的谷朊粉能够有效抑制冻干枣粉的吸湿，从而缓解结块的发生，保持流动性和分散性，进而提高冻干枣粉的品质。

Study of wheat gluten on hygroscopicity inhibition of freeze-dried jujube powder

Objective The effect of wheat gluten on hygroscopicity of freeze-dried jujube powder was studied. Methods The wheat gluten mixed with jujube pulp under different ratio, then passed through 60 mesh after freeze drying. Results Wheat gluten significantly reduced the equilibrium moisture content (EMC) of freeze-dried jujube powder. When the mass ratio of jujube to wheat gluten was 10:0, 7:3, 1:1 and 3:7, the hygroscopic isotherm curve exhibit that the adsorption type refers to J type growth, while the 0:10 samples belonging to S type growth. Thus, the addition of wheat gluten did not change the adsorption type of freeze dried jujube powder. The contact angle increased from 31.22° to 76.7° with the addition of wheat gluten, indicating that wheat gluten can reduce the surface wettability of freeze-dried jujube powder. Macroscopical and scanning electron microscopy images showed that the aggregates of freeze-dried jujube powder was gradually reduced with the increase amount of wheat gluten. Low-field NMR results showed that wheat gluten reduced the content of free water and inhibited the water to migrate towards a high degree of freedom. Conclusion A certain amount of wheat gluten can inhibit the hygroscopicity of freeze-dried jujube powder effectively, thereby alleviating the occurrence of caking, maintaining its fluidity and dispersity, improved the quality of jujube powder.