The Use of Edible Coatings Pre and Post-harvesting on the Quality Characteristics of Golden Delicious Apple (Malus domestica cv. Golden Delicious)

IntroductionThe rapid increase in population has raised concerns about food security in the world. On the other hand, to produce more food, in line with population growth, it is necessary to consider sustainable development goals so that the increase in production does not lead to excessive use of resources and environmental damage. Therefore, one of the effective ways to develop food security in line with sustainable development is to reduce the waste of agricultural products, especially garden products.Materials and MethodsThis study aims to investigate the effect of chitosan and essential oil foliar spraying pre- and calcium chloride immersion post- harvesting on Golden delicious apple fruits grafted on MM 111 (Malling Merton 111) in an 18-year-old apple orchard. A factorial experiment in the form of a completely randomized design and in four replications (each replication containing at least 30 fruits) was carried out in 2 hectares orchard located in the Abistan region of Khorram Abad city in 2021. The first factor of pre-harvest and post-harvest foliar treatments including control treatments (spraying solution with distilled water), foliar spraying of chitosan (100 mg/l) and essential oil (2500 mg/l), and immersion of harvested fruits with Calcium chloride solution (2 %) in the post-harvest stage, and the second factor is the storage period (in days 0, 60, 90 and 120 days after storage (which according to the high storage life of the apple fruit and performing the pre-test and until the end of life) Fruit storage was achieved. Results and DiscussionThe results of the analysis of variance showed that the effect of treatments and storage time on all desired characteristics was significant at the 1% level. Treated fruits had higher total phenolic and flavonoid content, antioxidant activity, vitamin C, and titratable acids and lower taste index, acidity, soluble solids, malondialdehyde, PPO activity and weight loss than the control. The highest amount of total phenol and flavonoid content, antioxidant activity, vitamin C, and titratable acids in all four measurement times belonged to chitosan + essential oil + calcium chloride treatment and the lowest amount was related to the control treatment. Also, in the control treatment, the amount of malondialdehyde, soluble solids, taste index and acidity increased during the storage period. In the fruits treated with chitosan + essential oil, the lowest acidity and soluble solids were observed, and in the chitosan treatment alone, higher titratable acids and the lowest taste index were observed. In general, based on the obtained results, it was observed that the application of chitosan and essential oil before harvesting and calcium chloride after harvesting improved the quality characteristics of Golden Delicious apple fruit. Weight loss is mainly caused not only by sweating but also by breathing. By forming a membrane on the surface of fruits, chitosan biopolymer acts as a mechanical and physical barrier to reduce gas exchange, and as a result, fruit maturation and aging are affected. Composite coatings reduce weight loss by maintaining hydration and reducing gas exchange and water vapor emission. Edible coatings can act on the phenylpropanoid pathway and increase the level of phenolic compounds in plants, and the phenylpropanoid pathway includes the synthesis of various plant secondary metabolites such as lignin, flavonoids, phenolic volatiles, and tannins. The semi-permeable barrier of the chitosan coating limited the rate of respiration, reduced water loss, and delayed ripening and aging, which resulted in higher total phenolic content during storage. Composite coatings delay the oxidation of phenolic compounds, eliminate metals and free radicals and create a quasi-bonded structure that prevents the passage of infiltrating materials such as O2, CO2, and water vapor.ConclusionIn this research, applying a combination of chitosan + essential oil + calcium chloride as a coating on apple led to increase the vitamin C, antioxidant activity, total phenol and flavonoid content, and reduction the weight loss. In addition, the application of this treatment led to the improvement of other characteristics such as the reduction of malondialdehyde, acidity, soluble solids, taste index, and increase of titratable acids. Therefore, it can be stated that in addition to the fact that these compounds alone improved the quality of apple fruit, their combined use is also recommended as a biodegradable and natural coating to increase the storage life of Golden Delicious apple fruit.