Extension of the Supercooled State Within Strawberry by Using the Combination of Pulsed Electric Field (PEF) and Oscillating Magnetic Field (OMF)

Highlights The PEF and OMF technique extended the strawberries’ supercooled state effectively. Strawberries stayed supercooled at -3.7°C, 2° below freezing point, for 11 days. The supercooled strawberries exhibited similar microstructure and microbiological state to fresh ones. Supercooled strawberries matched fresh ones in key quality indicators like drip loss, color, TA, pH, and SSC. Abstract. Supercooling is a promising food processing technique that significantly extends the shelf life of foods while preserving high quality. In this study, we used a pulsed electric field (PEF) and an oscillating magnetic field (OMF) to maintain strawberries in a supercooled state at -3.7 ± 0.1°C, about two degrees below their freezing point, for approximately 11 days. The treatment protocol involved a PEF duty cycle sequence of 0.8 for 300 seconds, 0.5 for 120 s, and 0.2 for 120 s, with an OMF at 1 Hz applied during the final phase to inhibit ice nucleation. We assessed microstructure, microbiological stability, drip loss, total soluble solids, and pH, and compared these factors to those of refrigerated (3.8°C), frozen (-7.8°C), and fresh strawberries. After 11 days, the quality of the supercooled strawberries was statistically comparable to that of fresh samples across all tested parameters. Microscopic analysis showed slight undulation in the cell walls of the supercooled samples compared to fresh ones, but the cells remained closely bonded without distortion. In contrast, refrigerated strawberries exhibited cellular damage due to natural degradation. The populations of total aerobic bacteria, yeast, and mold were significantly lower in the fresh, frozen, and supercooled samples compared to the refrigerated ones. Drip loss was highest in frozen strawberries at 11.72%, versus those supercooled or fresh. This study establishes a foundational process for long-term preservation of ‘fresh-like’ foods in the real food industry. Keywords: Oscillating magnetic field, Preservation, Pulsed electric field, Strawberry, Supercooling.