Robust stability and antimicrobial activity of d-limonene nanoemulsion by sodium caseinate and high pressure homogenization

Sodium caseinate (SC) derived from milk casein has excellent stability and emulsification properties. In this study, SC-stabilized d-limonene nanoemulsions were prepared for the first time by high pressure homogenization technique. Based on optimal conditions, the d-limonene nanoemulsions had the smallest particle size (d = 130 nm) and the highest negative surface potential. After placed at 4 °C for 60 days and heated at 90 °C for 1 h, the prepared nanoemulsions maintained their original particle sizes, indicating a high storage and thermal stability. In addition, the antibacterial activity of d-limonene against S. aureus was significantly increased by 5-fold after SC encapsulation. These results indicated that SC could be an outstanding natural component for stabilizing nanoemulsions to improve hydrophobic actives in food applications.