Development and Characterization of Carvacrol Nanoemulsions Stabilized by Bovine Serum Albumin‐Chitooligosaccharide Complexes

The intrinsic hydrophobicity, high volatility, and instability of carvacrol (CAR) limit its preservation and practical applications. This study developed a bovine serum albumin (BSA) -chitooligosaccharide (COS) nanoemulsion-based carrier system to improve CAR encapsulation efficiency. The pH-dependent formation of BSA/COS complexes was systematically analyzed, demonstrating significantly enhanced electrostatic interactions between BSA and COS at pH 6.0, which promoted the formation of insoluble complexes with minimal hydrodynamic diameter. Both microscopic morphology and hydrodynamic diameter confirmed that BSA/COS complexes effectively stabilized the CAR-loaded nanoemulsion system. At a 1:1 BSA/COS mass ratio, the emulsion exhibited the most minor hydrodynamic diameter and optimal uniformity (< 200 nm). Furthermore, compared with other groups, the B1C1-4 M group showed better environmental tolerance, such as acid, heat, and salinity, as well as the highest encapsulation efficiency. For example, compared to the B2C1-4 M group and the B1C2-4 M group, the B1C1-4 M group had the lowest hydrodynamic diameter increase rate of 12.98% after being stored at 4°C for 30 days, demonstrating the strongest stability. The mass ratio of BSA/COS and CAR concentration significantly affected the emulsion's antibacterial and antioxidant properties. The B1C1-8 M group achieved the highest antibacterial activity and free radical scavenging rates (88.2% for ABTS and 89.3% for DPPH, respectively). This study presents an innovative approach for enhancing the stability and functionality of CAR in food-grade applications.