低压静电场强度对冷冻沙棘叶品质的影响

Effects of Low-pressure Electrostatic Field-assisted Freezing at Different Field Strengths on the Quality of Sea Buckthorn Leaves

摘要:

【目的】探讨不同冷冻保鲜技术对沙棘（Hippophae rhamnoides）叶品质的影响。【方法】将低压静电场（low-voltage electrostatic field pretreatment， LVEF）技术应用于沙棘叶冷冻保鲜，探讨不同场强对沙棘叶冻结特性及活性成分保留的影响，分析不同静电场强度（距放电板0、20、40、60 cm）的沙棘叶冻结速率、水分损失率、活性成分保留率、抗氧化活性等，并与普通冷冻对比。之后将最优组和普通冷冻组的沙棘叶添加至牛奶中发酵制成沙棘叶酸奶，以普通酸奶（NY）为对照，测定其理化指标。【结果】距离静电板20 cm时，沙棘叶的冻结时间与普通冷冻相比缩短了16.6%，水分损失率为12.07%，黄酮与多酚保留率最高能达到新鲜沙棘叶的85.27%与90.97%，且DPPH和ABTS自由基清除率在低质量浓度时也能保持较高的水平，此外还能促进自由水向结合水迁移，减少沙棘叶在冷冻时的冰晶损伤。制成沙棘叶酸奶后，低压静电场处理沙棘叶组（LY）酸奶的黄酮、多酚质量分数分别比普通冷冻沙棘叶组（FY）高10.60%、15.70%，抗氧化能力显著增强（P<0.01）。【结论】LVEF能有效保留冷冻沙棘叶中的活性成分，改善其冷冻品质，为其产业化保鲜提供了理论依据。

Abstract:

[Objective] This study aimed to investigate the effects of different freezing preservation techniques on the quality of sea buckthorn (Hippophae rhamnoides) leaves. [Method] A low-voltage electrostatic field (LVEF) pretreatment was applied during the freezing process of sea buckthorn leaves, and its effects on freezing characteristics and bioactive compound retention were evaluated. Field strengths at 0, 20, 40, and 60 cm from the discharge plate were compared with conventional freezing in terms of freezing rate, water loss rate, bioactive compound retention rate, and antioxidant activity of sea buckthorn leaves. The optimized and conventionally frozen leaves were subsequently used to prepare sea buckthorn leaf yogurt, with plain yogurt (NY) as the control. Physicochemical indexess of the yogurt samples were determined. [Result] LVEF treatment at a distance of 20 cm shortened the freezing time by 16.6% and reduced the moisture loss rate to 12.07% compared with conventional freezing. The retention rates of flavonoids and polyphenols reached 85.27% and 90.97% of those in fresh leaves, respectively. In addition, the treated samples also exhibited strong DPPH and ABTS radical scavenging activities at low concentrations and promoted the conversion of free water into bound water, mitigating ice crystal damage. The yogurt prepared with LVEF-treated leaves (LY) showed increases of 10.60% and 15.70% in flavonoid and polyphenol content, respectively, compared with that prepared from conventionally frozen leaves (FY), along with enhanced antioxidant activity (P<0.01). [Conclusion] LVEF-assisted freezing effectively preserves the bioactive compounds and improves the freezing quality of sea buckthorn leaves, providing theoretical support for their industrial-scale preservation.