Formulation of MentholLoaded Nanostructured Lipid Carriers to Enhance Its Antimicrobial Activity for Food Preservation

Purpose: Due to the antimicrobial property, menthol have significant potential for food preservation and foodstuff shelf life improvement. Nevertheless, menthol instability, insolubility, and rapid crystallization in aqueous media make it unsuitable for used in food products. This work was aimed to prepare mentholloaded nanostructured lipid carriers (NLCs) to enhance its antimicrobial activity. Methods: Morphology, particle size and size distribution, encapsulation efficiency percent (EE%), and physical stability of the optimized formulation, prepared by hot melt homogenization method, were characterized by scanning electron microscopy, particle size analyzing, gas chromatography, and Xray diffraction (XRD) methods. Minimum inhibitory concentration and minimum bactericidal concentration of mentholloaded NLCs were evaluated and compared with conventional menthol emulsion against various Grampositive (Staphylococcus aureus, Bacillus cereus) and Gramnegative bacteria (Escherichia coli), as well as one fungus (Candida albicans). Results: Mentholloaded NLCs were spherically shaped nanosized (115.6 nm) particles with narrow size distribution (PDI eq; 0.2), suitable menthol EE% (98.73%), and appropriate physical stability after 90 days of storage period. XRD results indicated that menthol was in the amorphous form in the nanoparticles matrix. Antibacterial assay results revealed that the mentholloaded NLCs exhibited significantly higher in vitro antimicrobial property than conventional menthol emulsion. The results also indicated that mentholloaded NLCs had better effect on fungi than bacteria, and furthermore, antibacterial efficiency on Grampositive bacteria was higher than Gramnegative bacteria. Conclusion: In conclusion, NLCs could be a promising carrier for improvement of antimicrobial activity and preservation efficacy of essential oils in foodstuffs.