Nanoencapsulation of essential oils is a promising strategy for extending their antifungal activity and addressing evaporation and decomposition in unfavorable environmental conditions. This research aimed to synthesize and compare the physical properties of solid lipid nanoparticles (SLNs) containing peppermint essential oil (PE) during 12 months of storage at various temperatures (4°C, 25°C, 27°C with 60% relative humidity, 37°C, and 40°C with 75% relative humidity), and to investigate their antifungal activity compared to free PE. The SLN formulations were prepared using high-shear homogenization and ultrasound techniques and were analyzed using a particle size analyzer, differential scanning calorimetry, transmission electron microscopy, and microscopic images of fungal mycelium to assess encapsulation efficacy. The results showed that the PE-SLNs had a size of 164.2 ±5.8 nm, a PDI value of 0.176 ±0.01, a zeta potential value of –11.3 mV, and an encapsulation percentage of approximately 75 ±0.5%. Overall, the physical properties of the formulations showed a slight and acceptable increase over the 12-month storage period at all investigated temperatures. Furthermore, the in vitro inhibition percentage of free PE at a concentration of 2000 μL L–1 against Penicillium italicum and P. digitatum was 66.7% ±2.6 and 66.8% ±0.8, respectively, while for PESLNs it was 88.8% ±0.9 and 89.9% ±1.4. These results demonstrate the potential of SLNs as an effective carrier for sustained delivery of PE with improved antifungal activity during storage.

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