Control of Penicillium expansum in pears and apples by trans-2-hexenal vapours

The effects of trans-2-hexenal vapour treatment on Penicillium expansum, patulin content and fruit quality were evaluated in several cultivars of pears (“Abate Fetel”, “Bartlett” and “Kaiser”) and apples (“Golden Delicious” and “Royal Gala”). Fruit, wound-inoculated or non-inoculated, were treated at 20 °C with different concentrations of trans-2-hexenal over a 24 h period. Blue mould control, ranging from 50 to 98% (depending on cv), and reduction of patulin content were achieved when fruit were exposed to vapours from 12.5 μL L−1 of trans-2-hexenal 24 h after pathogen inoculation. In contrast, treatments applied 2 h after inoculation exhibited less efficacy or stimulated P. expansum infections. Trans-2-hexenal (12.5 μL L−1) did not affect fruit appearance, colour, firmness, soluble solids content or titratable acidity. Only in “Abate Fetel” pears phytotoxic symptoms developed within 3 days of treatment. Off-odours developed just after treatment, but the intensity decreased or disappeared during shelf-life. After 7 days at 20 °C following treatment (12.5 μL L−1) no significant differences in trans-2-hexenal content or in sensory traits were detected by a trained panel between untreated and treated “Golden Delicious” apples, while maintenance of off-flavours was perceived in “Bartlett”, “Abate Fetel” and “Royal Gala” fruit.