Certain physiological disorders during storage induce quality deterioration and reduce the shelf life of orange fruit. This study investigated the effects of a nano-emulsion (NE) composed of sunflower seed oil (SSO) and denak (Oliveria decumbens) essential oil (DEO), incorporated into a chia seed gum/gum Arabic (CSG/GA) based composite edible coating on the postharvest quality of Navel oranges during 40 days (d) of storage at 20 ± 1 °C and 40 % relative humidity. Physicochemical properties, ethylene production, and sensory attributes of fruit were evaluated at 10-day intervals. Scanning electron microscopy (SEM) images showed that the CSG/GA/NE coating effectively covered stomatal pores and formed a uniform membrane on the surface of the oranges. Results revealed that CSG/GA/NE and CSG/AG/SSO application significantly (P < 0.05) preserved total phenolic content (TPC), and total flavonoid content, as well as ascorbic acid content (AAC). It also inhibited polyphenol oxidase (PPO), and peroxidase (POD) activities leading to improved fruit quality. The treated oranges retained a higher juice content (43.18 %) while showing lower concentration of individual soluble sugars as determined by HPLC analysis, compared to other experimental groups. The oranges coated with CSG/GA/NE showed lower browning index (19.44 %), weight loss (15.53 %), ethylene production with higher hardness (28.05 N) and titratable acidity (0.61 %) while maintaining more acceptable sensory attributes during storage. Therefore, the coating composition of CSG/GA with 2.5 % nano-emulsion, can be used as a postharvest edible coating to maintain the quality of Navel orange fruit during shelf life.
Keywords: Browning index; Chia seed gum; Nano-emulsion; Non-enzymatic antioxidants Orange fruit.
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