Introduction

Cucumber (Cucumis sativus L.), is an economically important vegetable crop worldwide with short shelf-life that is mainly related to firmness loss, discoloration, desiccation and fungal rot. The reduction of losses resulting from bacterial and fungal rot is a major objective of postharvest technology for cucumbers, which tries to utilize safe and efficacious methods. Among postharvest fungal pathogens, the filamentous oomycete pathogen Phytophthora drechsleri is a common fruit-damaging agent in many vegetable crops such as Cucurbitaceae and Solanaceae families.

An interesting inhibitory effect of essential oils (EOs) and their constituents on food-related spoiling and pathogenic microorganisms have been demonstrated. Although use of EOs as food preservative is often limited due to stability considerations and low bioavailability since its bioactive compounds are chemically reactive species. In this regard, the nano-/micro-encapsulation of EOs allows protection of their sensitive bioactive compounds from unfavorable environmental conditions and enhances their bioactivity during food processing and storage.

 In this study the antimicrobial attribute of four natural essential oils including Zataria multiflora (ZEO), Cinnamomum zeylanicum (CEO), Mentha piperita L., and Thymus vulgaris was evaluated against phytopathogenic cucumber bacteria and fungi in laboratory culture media. ZEO and CEO which showed the best results were encapsulated in chitosan (CS) nanoparticles (EOs@CSNPs). EOs@CSNPs was characterized by ultraviolet and visible spectrophotometry, transmission electron microscopy, and dynamic light scattering. Then the efficacy of the CSNPs obtained under optimized conditions to inhibit phytopathogenic cucumber bacteria and fungi in culture media and as a coating on the cucumbers; as well as assessing the effect of two EOs@CSNPs coatings formula on physicochemical and microbial characteristics of the cucumbers during storage was investigated. According  to  experimental  results,  ZEO@CSNPs or CEO@CSNPs coatings can  be  an  alternative  method  with  which  to  extend  cucumber shelf-life.