Postharvest quality response of pears with beeswax coatings during long term cold storage
Lipid-based edible coatings are effective in maintaining the chemical and sensory characteristics of fruits for long-term storage by inhibiting the rate of respiration and transpiration. With this view, an investigation was conducted on the preservation of postharvest quality of pears using beeswax coating through modulating respiration and ripening associated enzymes during long term cold storage. Asian pears (Pyrus pyrifolia L. cv. ‘Patharnakh’) were coated with beeswax (0g, 20g, 30g, 40g L−1) and stored at 0˗1 ˚C and 90-95% relative humidity for 70 d. ‘Patharnakh’ pears were harvested from fully grown healthy trees, maintained under homogenous cultural practices at Punjab Agricultural University’s (PAU) Fruit Research Farm, Ludhiana (30.90 °N, 75.86 °E). Healthy and uniform fruits weighing 145 ± 5 g, having a firmness of 70 ± 2.5 N and soluble solid content of 12 ± 0.25 ⁰Brix was randomly picked in the morning during the two years of study. Plastic crates were used for collecting the fruits and immediately transferred to Post Harvest Laboratory which was subjected to coating treatments on the same d. The fruits were washed with sodium hypochlorite solution (2.5 ml L−1) and allowed to dry at ambient temperature (32 ± 2 °C). For storage studies, 80 uniform fruits were grouped randomly into 4 sets of 20 fruits for each replication under each treatment (16 lots x 80 in each treatment = total 1280). After treatment applications, fruits were air-dried and packed in the corrugated ﬁberboard boxes (CFB) and stored at 0˗1°C and 90–95% RH. The beeswax coated and uncoated fruits were analyzed at 30, 45, 60 and 70 d of cold storage. On the d of harvesting fresh fruit quality was also analysed. Results showed that the beeswax coatings-maintained fruit firmness and quality parameters and exhibited lesser activities of fruit softening enzymes pectin methylesterase, polygalacturonase and cellulase during the cold storage. Furthermore, at an optimum concentration beeswax coatings retarded the oxidative browning, a decline in ascorbic acid level and total phenolic content of pears. Nevertheless, at the end of storage, the highest concentration (40g L−1) of beeswax coatings exhibited higher browning index (BI) and polyphenol oxidase activity (PPO) even more than the untreated fruits. Therefore, the optimum concentration of 30g L−1 beeswax coating is suggested to preserve the quality of ‘Patharnakh’ pear through modulation of respiration and ripening enzymes during long-term cold storage.