Development of aroma compounds and sensory quality of ‘Royal Gala’ apples during storage

The effect of 1-MCP and CA storage on aroma production and consumer acceptance were investigated during storage of ‘Royal Gala’ apples. Fruit was harvested 132 d (Harvest 1) and 144 d (Harvest 2) after full bloom (DAFB), and stored under refrigerated air (RA; 0ºC; 90 – 95% RH), or in a controlled atmosphere (CA; 2.0 – 2.5 kPa CO₂, 1.8 – 2.0 kPa O₂), or treated at harvest with 625 nl l–¹ 1-methylcyclopropene (1-MCP)) followed by RA storage. Ripening indices, aroma volatile production, and sensory quality were determined after 2, 4 and 6 months of storage, plus 7 d of simulated shelf-life. Butyl acetate and hexyl acetate were the most abundant esters produced by ‘Royal Gala’ apple, and hexanol, butanol, and 2-methyl butanol were the most abundant alcohols. Hexyl acetate, 2-methyl butyl acetate and butyl acetate were found to be major contributors to aroma. CA storage and 1-MCP-treatment reduced ethylene production, softening and acidity loss. Storage of apples under RA conditions gave the highest levels of volatiles, while CA and 1-MCP treatment depressed aromatic volatile production in the fruit. At harvest, volatile emission was higher in late-harvested apples than in fruit picked at commercial harvest. After RA storage, no improvement in volatile emission was observed in late-harvested fruit; however, under CA or 1-MCP treatment, late-harvested fruit retained higher odour values than fruit harvested earlier. There was a good correlation between volatile levels and aroma intensity perceived by taste panelists; similarly high correlations were found between ethylene levels and most of the odour-active compounds analysed. 1-MCP and CA-stored fruit were preferred by consumers in all trials, indicating that both treatments can ensure ‘Royal Gala’ apples maintain their preferred textural characteristics. Therefore, this technology could be used to retain the quality of ‘Royal’ Gala fruit, especially during long-term storage.