Unveiling the protective mechanism of rapid microwave heating on Lactoferrin: insights from structural integrity and...

Lactoferrin (LF) is a heat-sensitive glycoprotein widely present in milk, known for its immunomodulatory and antioxidant activities. Conventional thermal processing in the dairy industry readily induces irreversible denaturation of LF, thereby diminishing its functional value. Microwave (MW) heating has attracted attention due to its rapid heating rate, energy efficiency, and environmental benefits. Although MW treatment shows potential for preserving LF, the underlying protective mechanisms remain unclear, particularly whether the effects are driven by rapid heating or by dielectric effects associated with MW. In this study, MW processing, conventional thermal (CT) processing, and MW-simulated conventional thermal (S) processing were applied at 70-90 °C to evaluate their effects on the structural stability, aggregation behavior, and bioactivity of LF. The results demonstrate that it is the heating rate, rather than dielectric effects, that predominantly governs LF preservation. Rapid MW heating allows LF to pass through the thermal denaturation temperature range (70-90 °C) within an extremely short time, thereby effectively preserving the integrity of its secondary and tertiary structures, inhibiting irreversible disulfide bond aggregation, and preserving iron-binding sites. In terms of biological activity, the antioxidant, anti-inflammatory, and anti-apoptotic activities of LF in the MW group were significantly superior to those observed in the CT and S groups. It could effectively protect RAW 264.7 cell viability and inhibit the secretion of inflammatory factors. These findings confirm that rapid MW heating effectively preserves the structure and bioactivity of LF, providing guidance for optimizing industrial MW pasteurization processes to improve the retention of functional proteins in dairy systems.