Abstract:
Carvone and spearmint essential oil vapours are suitable candidates for the control of
citrus postharvest pathogens due to their strong antifungal activity. However, the high volatility
of essential oils remains a hurdle that needs to be overcome before it can be applied as an alternative
fungicide. This work investigates the antifungal activity of 20 and 30 wt-% spearmint essential oil or
carvone, incorporated into ethylene–vinyl acetate (EVA) and linear low-density polyethylene
(LLDPE) strands postharvest pathogens affecting kumquats. Following the melt-extrusion process,
an average yield of 16–29 % and 15–28 % of the total carvone and spearmint essential oil, respectively, was determined in the polymer strands. Morphological studies using scanning electron
microscopy (SEM) revealed the presence of microporous structures in the internal structure of
the strands. The membrane-like skin that covers the polymer strand was also confirmed by SEM.
Variations in the release rates were observed between carvone and spearmint essential oils, which
was attributed to the difference in the vapour pressure of the neat essential oils. Furthermore, in
this study, the results demonstrated that the diffusion exponent ‘n’ of the Korsmeyer–Peppas, Weibull and Log-logistic models exceeded 1.0. In most cases, the Super Case II mechanism was
observed. In the case of the Mapossa model, as k2 was ˃> 1, it implies that the outer skin-like membrane covering the polymer strand fully controlled the carvone release. The application of the essential oil-loaded polymer strands resulted in a significant reduction in deterioration, caused by citrus.
