Plant phenolics as natural biocides in postharvest fungal disease

This research deals with the antifungal activity of naturally occurring phenolics, the metabolism of plant phenolics during the cold storage of fruits and vegetables in relation to fungal diseases, and the potential application of these natural substances as alternative fungicides. Changes in chlorogenic acid and flavonoids in the peel of Golden Delicious apples at harvest and during storage at 2 °C plus shelf-life at 20 °C have been investigated in relation to infections caused by Phlyctaena vagabunda. Chlorogenic acid was found to have inhibitory activity, while phloridzin showed no activity. Moreover, antifungal activity was observed in vitro when oxidized products of phloridzin were considered. Such an activity was increased by the simultaneous presence of chlorogenic acid. In addition 2,5-dimethoxybenzoic (DMB) acid was tested as an antifungal compound to control the postharvest decay pathogens of strawberry fruits. The effect of DMB acid treatments was investigated on the grey mould decay of strawberry fruits, stored at room temperature or at 3 °C plus a period of simulated shelf-life storage. A marked reduction in decay development was observed when commercially harvested strawberries were dipped or sprayed with 10-2 M DMB acid. Its practical use on berries in field conditions was tested. The best results were obtained when fruits were dipped for 1 minute in 10-2 DMB acid in combination with 0.05% (v/v) Tween 20.