不同碱性电解水预处理条件下枸杞变温控湿干燥特性研究

Effect of Alkaline Electrolytic Water Pretreatment on Temperature- and Humidity-controlled Hot Air Drying Quality of Wolfberry

摘要:

干燥效率低导致的能耗高、品质劣变是浆果类热风干燥加工面临的严峻挑战。在前期基于变温控湿的热风干燥研究基础上，为提高枸杞的热风干燥品质，采用不同碱性介质浸泡法（3%Na2CO3，碱性电解水分别处理1、10、20 min）对枸杞进行预处理，探讨其变温控湿干燥特性、微观结构、色泽、复水率、收缩率和营养成分。结果表明：相较于对照组，碱性电解水预处理促使枸杞热风干燥速率提高，显著降低了热风干燥过程中枸杞到达干燥终点所需时间 （P<0.05），碱性电解水预处理10 min，枸杞热风干燥时间最短，有效水分扩散系数为 5.020×10?8m2/min;碱性电解水预处理后，表皮蜡质条带间隙变大，甚至出现条带溶解、断裂的现象;碱性电解水预处理10 min 时，热风干制枸杞的色泽最接近于枸杞鲜样，复水率较高，收缩率较低，多糖质量分数、总酚含量和总黄酮含量均显著高于对照组 （P<0.05），分别为 9.79%、4.18 mg/g、6.42 mg/g;碱性电解水预处理后，枸杞果胶的组成发生显著变化，包含水溶性果胶、螯合性果胶和碱溶性果胶。枸杞鲜样中果胶主要为碱溶性果胶，碱性电解水预处理干燥后，螯合性果胶含量上升。综上，以碱性电解水对枸杞预处理10 min后干燥，枸杞热风干制品品质最佳。该研究为改善枸杞热风干燥提供了一种简单有效的预处理技术，同时也为其他浆果在干燥过程中的提质、增效提供了一种绿色、环保的技术方法。

Abstract:

The high energy consumption and quality degradation caused by low drying efficiency pose significant challenges in hot-air drying processing of fruits and vegetables. To enhance the hotair drying quality of wolfberry, pretreatment with different alkaline media soaking methods （3% Na2CO3 and alkaline electrolyzed water soaking for 1 min，10 min, and 20 min, respectively, was employed. The hot-air drying characteristics, microstructure, color, rehydration ratio, shrinkage，and nutritional content of wolfberry were investigated. The results revealed that compared with the control group, alkaline electrolyzed water pretreatment significantly reduced the hot air-drying time required for wolfberries （P<0.05）, with the shortest drying time observed in group treated by 10 min soaking of alkaline electrolyzed water. This group achieved a higher drying rate and an effective moisture diffusivity of 5.020×10?8 m2/min. After alkaline electrolyzed water pretreatment, the gaps between the waxy stripes on the epidermis were enlarged, with some stripes even dissolving or breaking. When pretreated with alkaline electrolyzed water for 10 min, the hot-air dried wolfberry exhibited the closest color to fresh samples, coupled with superior rehydration capabilities, reduced shrinkage and significantly elevated levels of polysaccharides （9.79%）, total phenols （4.18 mg/g），and total flavonoids （6.42 mg/g） compared with the control （P<0.05）. Pectin composition underwent notable transformations upon alkaline electrolyzed water pretreatment and drying. While fresh wolfberry primarily contained sodium carbonate-soluble pectin （SSP）, the content of chelator-soluble pectin （CSP） increased post-treatment, suggesting a reconfiguration of pectin fractions. In conclusion, pretreating wolfberries with alkaline electrolyzed water for 10 min produced the hot-air dried wolfberries with best quality. The research result can not only present a straightforward and effective pretreatment strategy for improving the hot-air drying of wolfberry but also can offer a green and environmentally benign approach for enhancing the quality and efficiency of drying processes for a wide range of fruits and vegetables.