Encapsulation of Peppermint Essential Oil ( Mentha piperita L.) in Gelatin‐Coated Solid Lipid Nanocarriers ( PEO ‐ SLNs

ABSTRACT

The primary objective of this work was to develop peppermint essential oil‐loaded solid lipid nanoparticles (PEO‐SLNs) and evaluate their effectiveness on microbial quality of trout fillets. PEO‐SLNs were prepared by bath sonication and characterized using dynamic light scattering (DLS), X‐ray diffraction (XRD), and Fourier transform infrared (FTIR). The optimized nanoparticles exhibited a zeta potential of −21.84 ± 2.25 mV, a mean particle size of 124.18 ± 0.22 nm, and a polydispersity index (PDI) of 0.20 ± 0.02. Trout fillets were randomly assigned to four treatment groups: Group 1, uncoated fillets; Group 2, fillet coated with 5% fish gelatin; Group 3, fillets coated with 5% fish gelatin containing 0.2% PEO; and Group 4, fillets coated with 5% fish gelatin containing 0.2% PEO‐SLNs. The treated fillets were stored at 4°C ± 1°C for 12 days, and microbiological analysis were performed throughout the storage. The highest reduction rates of total viable bacteria (1.20 log CFU/g), total psychrophilic bacteria (1.04 log CFU/g), Pseudomonas spp. (0.74 log CFU/g), Enterobacteriaceae (0.93 log CFU/g), Shewanella putrefaciens (0.73 log CFU/g), yeast and mold count (0.91 log CFU/g) were observed in the samples treated with gelatin‐loaded SLNs containing PEO. PEO‐SLNs demonstrated the highest overall microbial reduction, with statistically significant improvements compared with free PEO for four of the six evaluated microbial indicators. However, no significant difference was observed for Shewanella putrefaciens and Enterobacteriaceae . In addition, encapsulation of PEO in SLNs resulted in greater antibacterial activity than free PEO. These findings demonstrate that fish gelatin coatings incorporating PEO‐SLNs represent a promising natural preservation strategy for improving the microbial quality of trout fillets.