Control of postharvest blue and green molds of oranges by hot water, sodium carbonate, and sodium bicarbonate

Control of citrus blue mold, caused by Penicillium italicum, was evaluated on artificially inoculated oranges immersed in water at up to 75 degreesC f or 150 s; in 2 to 4% sodium carbonate (wt/vol) at 20 or 45 degreesC for 60 or 150 s; or in 1 to 4% sodium bicarbonate at room temperature for 150 s, f ollowed by storage at 20 degreesC for 7 days. Hot water controlled blue mol d at 50 to 55 degreesC, temperatures near those that injured fruit, and its effectiveness declined after 14 days of storage. Sodium carbonate and sodi um bicarbonate were superior to hot water. Temperature of sodium carbonate solutions influenced effectiveness more than concentration or immersion per iod. Sodium carbonate applied for 150 s at 45 degreesC at 3 or 4% reduced d ecay more than 90%. Sodium bicarbonate applied at room temperature at 2 to 4% reduced blue mold by more than 50%, while 1% was ineffective. In another set of experiments, treatments of sodium bicarbonate at room temperature, sodium carbonate at 45 degreesC, and hot water at 45 degreesC reduced blue mold incidence on artificially inoculated oranges to 6, 14, and 27%, respec tively, after 3 weeks of storage at 3 degreesC. These treatments reduced gr een mold incidence to 6, 1, and 12%, respectively, while incidence among co ntrols of both molds was about 100%. When reexamined 5 weeks later, the eff ectiveness of all, particularly hot water, declined. In conclusion, efficac y of hot water, sodium carbonate, and sodium bicarbonate treatments against blue mold compared to that against green mold was similar after storage at 20 degreesC but proved inferior during long-term cold storage.