This study aimed to develop tapioca-starch (2% w/v)-based edible coatings for the postharvest shelf life extension of Khasi mandarin (Citrus rediculata) during storage. The tapioca-starch-based coating formulations were prepared with the incorporation of essential oil compositions (clove, rosemary, basil, oregano, cinnamon, lavenders, tea tree, and thyme) with orange peel essential oils. The coating formulations were treated with the optimized conditions of ultrasonication (30 min at 50% amplitude).
The results showed that all the coating formulations maintained their nano size ranges between 206.9±4.51 nm and 656.5±3.47 nm, and zeta potential ranged between -20.8±1.1 mV and -9.7±0.9 mV on 85 days. The significantly (p<0.05) higher particle size (3564±6.51 nm) and lower value of zeta potential (-3.6±0.4 mV) were found in CF0 (tapioca starch without the addition of EO and ultrasonic treatment) coating formulations. The shelf-life study result showed that the application of starch-based nano-formulations was significantly effective in maintaining higher postharvest characteristics in fruits as compared to controls (distilled water) throughout the storage period. The control samples were spoiled at up to 20 days. They showed (p<0.05) higher weight loss (34.36 g), higher total soluble solids (10.03°Bx), firmness (1709.476 g. Force), and higher respiration rate (16.26 mL CO2 kg-1 h1) with a higher maturity index on 20 days of storage, significantly. A significantly higher reduction in antioxidant activity (21.65%) and total phenolic content (38.01 mg/g) was also observed in control samples with higher microbial load (yeast and mold) on 20 days of storage. The CF3 and CF8 nano-coatings were most effective in maintaining the higher postharvest quality attributes of Khasi mandarin during storage as primary packaging and combined with secondary packaging. This study suggests that the incorporation of essential oils and ultrasonic treatments has the potential to maintain the integrity of coatings and improving the shelf life of mandarin fruits.
