Edible coatings maintain the phytochemicals in cold-stored ‘Kinnow’ mandarin (Citrus nobilis Lour x C. deliciosa Tenora) fruit

Abstract

Edible coatings usually maintain or improve the scavenger antioxidants and activities of defense-related enzymes consequently preserve the bioactive compounds. The effects of different coating treatments e.g. carboxymethylcellulose (CMC; 1.0, 1.5 and 2.0 g L-1), chitosan (0.5, 1.0 and 1.5 g L-1), beeswax (5, 10 and 15 g L-1) and control (uncoated fruit) and cold storage period (5-7 ºC, 90-95 % RH for 75 days) on the levels of total phenols, total antioxidant activity, flavonoids, protein, total free amino acids and sugars (total and reducing sugars) in the juice of cold-stored ‘Kinnow’ mandarin fruit were assessed in 2017-18 and 2018-19. The fruit used in the experiment were harvested from the fifteen-year-old healthy trees previously grafted on rough lemon rootstock (Citrus jambhiri L.) and grown in the same block. The fruit coated with different coating treatments were stored at 5-7 ºC and 90-95 % RH for different storage periods (0, 30, 45, 60 and 75 days). The levels of total phenols, flavonoids, total antioxidant activity, total and reducing sugars in the fresh juice of the cold-stored fruit were determined following each cold storage period. Amongst different coating treatments tested, CMC (2.0 g L-1) coating proved to be the best treatment to maintain highest levels of bioactive compounds viz., total phenols, total antioxidant activity, flavonoids and total and reducing sugars as compared to the control during cold storage. In conclusion, coating with CMC (2.0 g L-1) was effective to extend the cold storage life and maintain the highest levels of health-promoting compounds in ‘Kinnow’ mandarin fruit without any symptoms of its toxicity to the fruit