Micellar Casein as a Nanocarrier for Carvacrol: Binding Mechanism, Antioxidant Activity, and Antimicrobial Activity against Escherichia coli

In this study, micellar casein (CS) and carvacrol (CARV) nanoparticles were successfully prepared by altering the pH of the medium. Fluorescence analysis confirmed that the hydrophobic interactions are the primary forces in the CS-CARV complex. Fourier transform infrared spectroscopy (FTIR) data revealed structural modifications following nanoencapsulation and ultrasound application. The insertion of CARV into the CS structure led to a size reduction, indicating that CARV interacts with the hydrophobic interior of the CS, approaching its protein fractions. The formed nanoparticles showed antioxidant potential, although they did not consistently outperform free CARV. The antimicrobial activity of CARV against Escherichia coli was enhanced after nanoencapsulation (↓87% for minimum inhibitory concentration, MIC, and ↑ 40% for the diameter of the inhibition zone). The nanoencapsulation of CARV within the CS protected against temperature, light, and phase separation over time. Despite sonication, which reduced the size and polydispersity of the nanoparticles, no significant improvements in antimicrobial activity and stability were observed that would justify its use.