Abstract
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
menthol-loaded 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 X-ray diffraction (XRD)
methods. Minimum inhibitory concentration and minimum bactericidal
concentration of menthol-loaded NLCs were evaluated and compared with
conventional menthol emulsion against various Gram-positive (Staphylococcus
aureus, Bacillus cereus) and Gram-negative bacteria (Escherichia coli),
as well as one fungus (Candida albicans).
Results: Menthol-loaded
NLCs were spherically shaped nanosized (115.6 nm) particles with narrow size
distribution (PDI = 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 menthol-loaded NLCs exhibited significantly
higher in vitro antimicrobial property than conventional menthol
emulsion. The results also indicated that menthol-loaded NLCs had better effect
on fungi than bacteria, and furthermore, antibacterial efficiency on
Gram-positive bacteria was higher than Gram-negative bacteria.
Conclusion: In conclusion,
NLCs could be a promising carrier for improvement of antimicrobial activity and
preservation efficacy of essential oils in foodstuffs.