Maintaining postharvest quality of raspberries with natural volatile compounds

The postharvest quality of raspberries (Rubus idaeus L.) was evaluated after treatment with several natural volatile compounds and storage at 0, 10 or 20 degreesC. At high storage temperature (20 degreesC), raspberries deteriorated rapidly and none of the natural volatile compounds that were used were effective in extending storage life of the fruit. At low storage temperature (0 degreesC), little difference could be discerned among the various volatile treatments. However, at 10 degreesC storage, raspberries treated with methyl jasmonate (MJ), allyl isothiocyanate (AITC), tea tree oil (TTO), or absolute ethyl alcohol had less decay. MJ- and TTO-treated fruit also maintained higher levels of sugars, organic acids and oxygen radical absorbance capacity compared with untreated fruit. Samples treated with acetic acid or vinegar vapour did not differ from control fruit. Measurement of oxygen and carbon dioxide concentrations within the containers during storage revealed that none of the treatments caused accumulation or depletion of these gases to a level that would be harmful to raspberries. Colour measurements of the berries showed that all raspberry fruit became darker and less red after storage, but fruit treated with MJ were found to have the highest intensity of red colour while AITC application caused the berries to appear lighter in colour.