2017 ASHS Annual Conference

Off-flavor development in mandarins is associated with a decline in internal oxygen following the application of a wax coating during postharvest processing. Characteristics of the peel can influence the rate of oxygen diffusion into the fruit and alter internal oxygen levels. Degreening of mandarins, generally practiced during the early portion of the season, causes some degree of peel desiccation that could potentially change peel gas permeability and affect both the entry of oxygen into the fruit and subsequent flavor. To test this possibility unwaxed ‘W. Murcott’ and ‘Gold Nugget’ mandarins were stored at 20 °C and either 80% or 90% RH for 1 to 4 days prior to waxing to simulate a potential degreening scenario. The fruit were then waxed with a carnauba wax and stored for 2 weeks at 5 °C followed by 1 week at 20 °C, at which time fruit internal atmospheres were determined. Weight loss was similar for both varieties during the simulated degreening and averaged 0.7%/day at 80% RH and 0.4%/day at 90% RH, with the total weight loss after 4 days being 2.9% and 1.8%, respectively. Oxygen concentrations were significantly different between the varieties, averaging 6.1% for ‘W. Murcott’ versus 9.0% for ‘Gold Nugget’ but did not differ due to either storage humidity or days of storage prior to waxing. In further experimentation the effect of enhanced peel dehydration was determined by placing fruit in a specially-constructed device that maintained a constant airflow over the fruit for periods of 24 hours, 48 hours, or 72 hours after which the fruit were waxed, stored for 2 days at 20 °C, and internal oxygen concentration determined. Even after 72 hours and 5.0% weight loss internal oxygen concentrations did not differ from that of fruit that received no dehydration treatment. Gas exchange through the peel appears to be fairly resilient to fruit desiccation and suggests that the degree of water loss that occurs from the peel during degreening likely does not directly contribute to off-flavor development in mandarins.