Storage of sweet cherries in low oxygen and high carbon dioxide atmospheres

Acetaldehyde and ethanol are already present in detectable levels at the time of harvest, under aerobic conditions and in healthy, undamaged fruit. Both metabolites can be detected, at different concentrations, in all cultivars. Several hours after harvest, the levels of acetaldehyde in cultivars Summit, Techlovan and Kordia were 6.41, 9.78 and 22.00 mg/l, respectively. Both ethanol and acetaldehyde accumulate to significant levels in anaerobically stored cherries, particularly in atmospheres with high levels of CO2. The highest levels of ethanol observed, after 31 days of exposure to anaerobic conditions, were in the cultivars Techlovan (1,159 mg/l) and Summit (1,168 mg/l); both concentrations are are broadly similar. The metabolites decreased after a return to aerobic conditions, but remained higher than the levels first observed. Sweet cherries stored in anaerobic conditions are also sensitive to the development of off-flavours in the first 24 hours after opening the storage box. The very slow ripening of the fruit under anaerobic conditions was satisfactorily quantified by measuring the higher degree of fruit firmness, when the usual, visual attributes of ripeness were almost undetectable. Stems also remained green, in contrast to the usual browning that occurs under normal atmospheres. Discrimination analysis of various parameters observed gave a good resolution of different cultivars.