Use of Food Additives to Control Postharvest Citrus Blue Mold Disease

The aim of this study was to find an alternative to the chemical fungicide currently used in the control of postharvest citrus diseases. The antifungal activity of 10 salt compounds, considered as common food additives was assayed in in vitro and in vivo trials against Penicillium italicum, causal agent of citrus blue mold. Among the 10 tested salt compounds, sodium carbonate, ammonium carbonate, copper sulfate, sodium EDTA and sodium metabisulfite completely inhibited mycelial growth of Penicillium italicum at 20 mM. Colony growth of P. italicum on pH adjusted medium was evaluated. Results indicate that P. italicum can grow on both acidic and alkaline pH, with the optimum growth occurred in the range of 4.0 and 8.0. Results of the in vivo trials with tested salt compounds indicate that sodium metabisulfite (100 and 200 mM), boric acid (400 mM), sodium salicylate and sodium sulfite (200, 300 and 400 mM) completely inhibited blue mold development on citrus fruit. Boric acid (400 mM) and sodium metabisulfite (100 mM) gave the best results as they completely inhibited the fungus development without damaging fruit rind. Such healthy products therefore may represent a sustainable alternative to the use of chemical fungicides for controlling postharvest diseases of citrus fruit.