Effect of nano-chitosan and acetic acid on quality characteristics of cold-stored grape cv. Rasheh.

Grape fruit contains some nutrients and high amounts of biologically active phenolic substances, but fungal decay and quality loss are important factors limiting its shelf-life for fresh-consuming and export. Rasheh vine (Vitis vinifera cv. Rasheh) is mainly grown in rainfed vineyards in the western half of Iran, and its berries are rich in anthocyanins, flavonoids and soluble solids. In this study, the effect of natural coatings of nano-chitosan and acetic acid on the post-harvest quality characteristics of Rasheh grape fruit was investigated. Nano-chitosan suspension with a particle size distribution of 5-30 nm was prepared in acetic acid solution by the conventional ionic gelation method. Grape fruits were coated by immersion in the nano-chitosan suspension (0.2%), acetic acid solution (0.5%) or distilled water (control) for 1 min and their microbial, physicochemical and sensory properties were measured during 8 weeks storage at 4 °C and 90% relative humidity. In general, the fruits coated with nano-chitosan or acetic acid had lower aerobic mesophilic bacteria count, mold and yeast count and decay percentage, and higher firmness, soluble solids, titratable acidity and vitamin C, as well as, better sensory properties, compared to the control. The nano-chitosan was more effective than acetic acid in improving the post-harvest quality and shelf life of grape fruit. No significant difference was observed in the weight loss percentage and pH values of the samples. Therefore, the nano-chitosan suspension prepared in acetic acid solution, as a natural and customer-friendly coating, is suitable for improving the shelf-life and post-harvest quality of grape fruit, but some of its beneficial effects are due to acetic acid.