Effect of hot water treatment on postharvest control of Penicillium expansum and Botrytis cinerea of apples

A hot water treatment was used by dipping to evaluate its efficacy for the reduction of Botrytis cinerea and Penicillium expansum development on 'Golden Delicious' apples. Fruit were artificially wounded and inoculated with 30 µL of 1×10⁴ conidia mL^‑1 suspension of either P. expansum or B. cinerea. The inoculated apples were left to air dry at 24±1°C. After 2 h, the fruit were immersed in hot water for 50-75°C × 30-900 s. Control fruit were dipped in tap water (20°C) or were not treated. Treated fruit were subsequently stored at 25°C for seven days after which wounds were examined and the percentage of disease incidence was determined. The disease incidence of P. expansum was reduced by hot water treatments at 60°C for 60 s (40%), compared to the control fruit (100%), without causing any skin injuries. Furthermore, a hot-water dip at 60°C for 60-90 s, reduced grey mould development in inoculated wounds to 30% compared with control fruit treated with tap water (100%), without causing any skin injuries.