Postharvest challenges for the four main apple cultivars in Norway

The four main apple cultivars in Norway, ‘Discovery’, ‘Summerred’, ‘Red Gravenstein’, and ‘Red Aroma’, account for approximately 80% of the market volume. These cultivars provide good yields in a Nordic climate with a short growing season but have relatively limited storage and shelf life. The main challenges are the rapid loss of firmness and senescence-related disorders, both of which are connected to ripening and ethylene. Several projects investigated possible ways to secure fruit quality at the consumer level by improving conditions at the packinghouse. One of the factors to evaluate was ethylene levels in fruit storage rooms. Ethylene concentrations were measured in cold storage rooms with varying volumes of fruit using a portable instrument equipped with an electrocatalytic sensor for continuous, in-situ measurement of ethylene in the air. Ethylene concentrations between 10 and 35 ppm were measured in 18% of the rooms, whereas 82% had concentrations between 0 and 10 ppm. Fruit samples were assessed for ethylene production rates in their expected cold storage period. The values obtained were used to evaluate the risk of high ethylene levels in certain rooms before packaging, to recommend which cultivars could be kept in the same rooms, and for how long. Treatment with 1-methylcyclopropene (1-MCP) was also tested to improve fruit quality during storage further. The 1-MCP treatment revealed considerable potential for maintaining the postharvest quality of the tested Norwegian apples.