RELATIONSHIPS BETWEEN PREHARVEST HORTICULTURAL OIL APPLICATION AND POSTHARVEST BEHAVIOUR OF ´GOLDEN DELICIOUS´ APPLES: EFFECT ON VOLATILE AROMA PRODUCTION

Abstract

Traditionally, petroleum-based horticultural oils are applied throughout the growing season to apples (Malus ×domestica Borkh.), although plant-based oils, like soybean oil, have shown to be just as effective. However, the influence of oil applications on fruit quality and storage behaviour of apples is not well understood. To study the effect of growing season-applied soybean oil on volatile aroma production, three single treatments (midseason, 21 days before harvest, 3 days before harvest) of soybean oil emulsion (1% food grade oil, 0.1% Latron surfactant) were administered. 'Golden Delicious' apples were harvested at commercial maturity and stored for up to 6 months at 0.5°C in air (RA) or under 2 kPa O 2 and 0.2 kPa CO 2 controlled atmosphere storage (CA). Application of soybean oil emulsion 21 days before harvest resulted in apples with consistently higher mean volatile production, mainly due to aldehyde (hexanal, 2-hexenal) levels higher than controls. The loss of alcohols (mainly butanol, 2-methylbutanol) due to prolonged CA storage was diminished by oil-treated fruit. More alcohols (butanol, 2-methyl butanol) were regenerated after 7 days of shelf-life. Compared with control fruit, only apples treated with soybean oil emulsion 3 days before harvest emitted higher amounts of esters (butyl acetate, 2-methyl butyl acetate) corresponding to the alcohol precursors. The application of soybean oils during the growing season may potentially improve the retention and regeneration capacity of important volatile compounds contributing to the aroma of 'Golden Delicious' apples.