Inhibition of Penicillium expansum by an oxidative treatment

Several oxidizing compounds such as sodium hypochlorite (NaClO) and hydrogen peroxide (H2O2) are used to control postharvest decay in fresh fruit due to their antimicrobial effects. Here, we applied these compounds in vitro, in the presence of CuSO4, against Penicillium expansum, causal agent of apple blue mold. MICs were 50 mg L−1 and 400 mmol L−1 for NaClO and H2O2, respectively, when these compounds were individually applied to conidia suspensions during 2 min. A combined oxidative treatment (OT) consisting on an incubation with 1 mg L−1 NaClO and 200 mmol L−1 H2O2, in the presence of 6 mmol L−1 CuSO4, inhibited growth, conidial germination and fungal infectivity on apple. The fractional inhibitory concentration index for the interaction between NaClO and H2O2 in the OT was 0.52 indicating a synergistic effect of the oxidizing compounds. These results suggest that the OT could be an interesting alternative for apple diseases postharvest control.