Response of raspberry cultivars and selections to controlled atmosphere storage

Nine red raspberry (Rubus idaeus L.) cultivars and advanced selections from the Agriculture and Agri-Food Canada breeding program were assessed for their potential market-life when held at 1°C in air or controlled atmosphere (CA, 12.5 kPA CO₂/7.5 kPa O₂) with 95% RH over two seasons. At harvest, fruit were assessed for firmness, soluble solids, titratable acids as well as sugar, acid and volatile composition. Fruit in 16-fruit samples were individually assessed every 2-3 days for decay and physiological breakdown (PB). Decay and PB development were determined as the number of days (lag) before the first sign of deterioration. The rate of fruit loss was calculated as a linear rate of deterioration following the lag period. Fruit decay of all genotypes was strongly suppressed by CA storage with the lag period extended to >45 days compared to 19-29 days for genotypes stored in air. The lag of PB, which was expressed as juice leakage, ranged from 6 to 28 days in air-stored fruit and was increased by -1.0 to 9.7 days in CA-stored fruit depending on genotype. Fruit sugar content averaged 51% fructose, 26% glucose and 23% sucrose and acids averaged 75% citric, 13% quinic, 6% succinic and 6% malic acids, but varied among genotypes. Volatile composition was dominated by C13 norisoprenoid, which comprised 65-93% and monoterpenes, which comprised 2.6-20.2% of total volatiles. Initial firmness strongly correlated with PB resistance during storage but no relationship between sugar and acid content and fruit storage-life was found. Fruit of genotypes with the longest market-life when held in air or CA included 'AAC Eden', 'K03-9', 'Glen Ample' and 'K02-15' and those with the shortest market-life were 'Encore', 'Nova', 'K02-14', and 'K06-1'.