Pre-harvest application of soybean oil alters epicuticular wax crystallisation patterns and resistance to weight loss in ‘Golden Delicious’ apples during storage

Abstract

SummaryThe effect of field-applied soybean oil emulsion on weight loss during storage, development of cuticular cracks, and epicuticular wax crystallisation patterns in apples was studied using three orchard locations in Washington State, USA. Three single treatments (mid-season, 21 d before harvest, and 3 d before harvest) of soybean oil emulsion [1% (v/v) food grade soybean oil; 0.1% (v/v) emulsifier Latron B-1956®] were administered to ‘Golden Delicious’ apples. Apples were harvested at commercial maturity and stored for up to 180 d at 0.5°C in refrigerated air or under controlled atmosphere storage conditions (2 kPa O2 and 0.2 kPa CO2).The rate of weight loss decreased in all soybean oil-treated apples. Orchard location and humidity conditions during storage also influenced the amount of weight loss seen for all oil-treatment timings. As observed by scanning electron microscopy, ‘Golden Delicious’ apples developed cracks that intensified with maturity. Crack development was also influenced by orchard location. Pre-harvest application of soybean oil emulsion decreased the occurrence and severity of cuticular cracks in susceptible cultivars such as ‘Golden Delicious’, with treatments applied closer to harvest being most beneficial. The rate of weight loss during storage was directly related to the development of cracks. All apples showed altered wax crystallisation patterns after the application of soybean oil.