Efficient Production of High-Concentration Lycopene Nanoemulsions by an Evaporation Technique: A Response Surface...

Lycopene, which exhibits a brilliant bright red color, has considerable potential for application in the food industry. However, its utilization is severely limited by its extremely high hydrophobicity and crystallinity. Emulsification represents one possible strategy to overcome these limitations; nevertheless, most previous studies have focused on low lycopene concentrations or turbid emulsions with large particle sizes. Therefore, this study aimed to optimize a preparation method for high-concentration lycopene nanoemulsions using an evaporation technique. Lycopene nanoemulsions were prepared under systematically designed conditions, with surfactant concentration ( $x_{\mathrm{SE}}$ ) ranging from 0.16% to 1.84%, lycopene concentration in the dispersed phase (ethyl acetate) ( $x_{\mathrm{lyc}}$ ) from 9.6 to 110.4 µg/mL, and dispersed phase ratios relative to the total emulsion ( $x_{\mathrm{DPR}}$ ) from 3.2% to 36.8%. Optimization was performed with respect to the encapsulated lycopene concentration, encapsulation efficiency, and mean particle diameter. The optimal conditions for achieving a high lycopene concentration were determined to be 0.895% $x_{\mathrm{SE}}$ , 110.4 µg/mL $x_{\mathrm{lyc}}$ , and 36.8% $x_{\mathrm{DPR}}$ . Under these optimized conditions, the encapsulated lycopene concentration reached 36.4 µg/mL, which was in good agreement with the value predicted by response surface analysis (35.06 µg/mL). Furthermore, the storage stability of the optimized lycopene nanoemulsion was evaluated at 5°C, 25°C, and 45°C for 4 weeks. The results showed that the decrease in encapsulated lycopene concentration followed first-order kinetics and corresponded to the Arrhenius equation, with rate constants of 0.0175, 0.0258, and 0.0679 day^-1 at 5°C, 25°C, and 45°C, respectively. These findings indicate that the prepared nanoemulsion exhibits high thermal stability.