Optimizing Pulsed Magnetic Field Parameters for Microbial Safety and Quality in Orange Juice

Nonthermal technologies have garnered significant attention for fruit juice preservation due to the increasing consumer demand for fresh, high-quality, and nutritious products. These methods, being eco-friendly, effectively inactivate microorganisms and enzymes without compromising the sensory and nutritional qualities of juices. Among these, pulsed magnetic field (PMF) technology is a promising technique that involves exposing liquid foods to a magnetic field in the form of pulses, exhibiting a bactericidal effect without any rise in temperature. The study aimed to develop a PMF processing system capable of generating low-frequency, high-intensity oscillating magnetic fields and optimized its application on orange juice at varying concentrations (10%, 15%, and 20%), magnetic field intensities (2, 4, and 6 T), and treatment times (5, 10, and 15 min). Additionally, the process conditions were optimized to preserve the nutritional quality, sensory properties, and microbial safety of orange juice. Fresh orange juice had an initial bacterial load of 2.09 × 10⁶ CFU/mL, which was reduced to 1.43 × 10⁴ CFU/mL at 4 T for 15 min in 15% juice. Similarly, yeast and mold counts decreased from 1.85 × 10⁵ to 1.68 × 10⁴ CFU/mL in 20% juice. The nonthermal nature of PMF was confirmed by negligible temperature rise. Posttreatment, L-values ranged from 82.4 to 83.79, decreasing to 80.2–82.55 during storage, while b-values ranged from 16.48 to 16.96, slightly reducing to 16.34–16.86. Viscosity for 10% juice ranged from 0.0645 to 0.0687 Pas posttreatment, reducing to 0.06–0.0648 Pas after 10 days. Minimal pH variation was observed. The optimal PMF treatment (4 T, 15 min, 20% concentration) effectively reduced microbial load while preserving juice biochemical (pH, color) and rheological (viscosity) during storage at 4°C. PMF-treated orange juice showed minimal changes in color, viscosity, and microbial stability during refrigerated storage. The absence of heat-related degradation ensures retention of quality attributes. This study demonstrates that PMF is a viable, nonthermal alternative for processing high-acid fruit juices, providing a balance between microbial safety and quality preservation.