Effect of Ultrasound Pretreatment Combined with Magnetic Field-Assisted Freezing on Bioactive Compounds and Antioxidant Capacity of Blueberry

Magnetic field-assisted freezing is a novel freezing technology for improving food quality. The purpose of this study was to evaluate the effect of ultrasound pretreatment in combination with a static magnetic field on frozen blueberry bioactive compounds and antioxidant capacity. Blueberries were subjected to ultrasound pretreatment and frozen by using a static magnetic field. Bioactive components, antioxidant properties, organic acids, and the flesh color of blueberry were analyzed. The results demonstrated that, compared with -20 °C control freezing (CF), the ultrasound pretreatment combined with static magnetic field freezing (U-MF) better maintained blueberry bioactive components. The anthocyanin and total phenolic and flavonoid contents of U-MF were 33.67%, 29.14%, and 18.65%, respectively, higher than the CF group (<i>p</i> < 0.05). The DPPH and ABTS free radical scavenging capacities of U-MF were 53.87% and 15.14%, respectively, higher than those of the CF group (<i>p</i> < 0.05). This article provides a theoretical basis for the application of magnetic fields in the frozen preservation of fruits and vegetables.