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.