Short Exposure to High CO2 and O2 at Curing Temperature to Control Postharvest Diseases of Citrus Fruit.

Curing of citrus fruit at 30 to 37°C and 90 to 98% relative humidity for 65 to 72 h is an effective alternative to fungicides to control postharvest green and blue molds caused by Penicillium digitatum and P. italicum, respectively. However, commercial adoption is limited because treatment is long and it may harm fruit quality. In order to improve the feasibility of curing, short CO2 or O2 exposures at curing temperature were evaluated on 'Nadorcott', 'Clemenules', and 'Ortanique' mandarin fruit and 'Valencia' orange. Fruit were artificially inoculated, exposed 24 h later to air (control); CO2 at 15, 30, 50, or 95 kPa; or O2 at 30 or 45 kPa at 20 or 33°C for 8, 24, or 48 h and incubated at 20°C for 4, 7, or 15 days. Exposure at 33°C with CO2 at 15 kPa for 24 h or O2 at 30 kPa for 48 h effectively controlled both green and blue molds after 7 days of incubation at 20°C; however, control of both diseases was minimal after 15 days. To assess potential induction of disease resistance, fruit were treated as described above, then inoculated after 1, 2, or 5 days at 20°C and evaluated after 3 and 6 more days at 20°C. All of the treatments were ineffective in inducing fruit resistance. Short exposures of citrus fruit to high CO2 or O2 at curing temperatures may be part of a control program alternative to synthetic fungicides, especially for organic fruit markets.

Effect of solid content and composition of hydroxypropyl methylcellulose-lipid edible coatings on physico-chemical and nutritional quality of 'Oronules' mandarins.

BACKGROUND: Citrus fruit represent an important source of vitamin C, as well as other bioactive compounds. Edible coatings have the potential to extend shelf life of citrus by providing a semi-permeable barrier to water and gases, which depends on coating composition, solid content (SC), and cultivar. However, little is known about the effect of coatings on citrus nutritional quality. This work studies the effect of coating composition and SC of hydroxypropyl methylcellulose (HPMC)-beeswax (BW)-shellac coatings on the physico-chemical, sensory and nutritional quality of 'Oronules' mandarins. Coatings prepared at the same lipid content differed in the BW:shellac ratio (1:3 and 3:1) and SC of the formulations (40 and 80 g kg⁻¹). RESULTS: The coating with 1:3 BW:shellac ratio and 80 g kg⁻¹ SC was the most effective controlling weight loss, although it was less effective than the commercial wax tested. Increasing SC had a greater effect than the BW:shellac ratio in fruit internal atmosphere and sensory quality, with the presence of off-flavour when coatings were applied at 80 g kg⁻¹ SC. Nutritional quality was not affected by the application of the different treatments. CONCLUSION: HPMC-lipid coatings have the potential to extend shelf life of 'Oronules' mandarins. However, care should be taken controlling formulation SC to avoid the build-up of off-flavour.