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.
