Effects of static magnetic field-prolonged supercooling preservation on blueberry quality

Although refrigeration and freezing are commonly used methods for preserving blueberries, refrigeration is only suitable for short-term preservation (storage at 4 °C for approx. 1 month), whereas ice crystals that form during freezing can lead to a degradation of blueberry quality. However, supercooling, which combines the advantages of freeze-free low-temperature storage, offers a novel alternative preservation method. In this study, we demonstrate that 10 mT static magnetic field treatment reduces the nucleation temperature of blueberries to below −6 °C and enhances their supercooling. The combination of static magnetic and temperature fields was found to prolong the effective storage of supercooled blueberries for up to 35 days, during which time, we detected no ice nucleation. Compared with refrigeration and freezing, the firmness of the supercooled-preserved blueberries increased by 24.1% and 31.2%, respectively, with corresponding reductions of 3.8% and 4.69% in weight loss. These changes were associated with a retardation of the decline in organic acid and soluble solid contents, along with the maintenance of high total phenolic and anthocyanin contents, antioxidant capacity, and the activities of polyphenol peroxidases and peroxidases. Collectively, our findings in this study indicate that supercooling would be an effective new approach for the preservation of blueberries.