Inhibition of Kumquat Postharvest Fungi through Vapor Contact with Spearmint Essential Oil and Carvone
Katlego Phala, Wilma Augustyn, Sandra Combrinck, Ben Botha, Thierry Régnier, Wilma du Plooy
Abstract
The antimicrobial activities of spearmint essential oil and six of its constituents were evaluated in vitro and in vivo analysis using direct contact and vapor exposure assays. Qualitative analysis of spearmint essential oil revealed that the main constituents of the essential oil are carvone (62.0%) and limonene (24.6%). Limonene (45%) was found to be the major constituent of the essential oil vapor phase, when sampled using direct headspace and Tenax TA tubes. Spearmint essential oil, carvone, and 1,8-cineole exhibited the highest antifungal activity against Penicillium digitatum and Geotrichum citri-aurantii (Ferraris), with the vapor phase application resulting in more than 50% growth inhibition at 1429 mg/L for 1,8-cineole and complete inhibition occurring at 714 mg/L for carvone and spearmint. The treatment of kumquats with spearmint essential oil and carvone vapors resulted in an average reduction in weight loss and decay rate of approximately 30% and 40%, respectively, when the fruits were stored at 25 °C.