Dynamic controlled atmosphere (DCA): a chance for sustainable storage of fruit, maintaining quality and better volatile profile

The development of modern storage systems went from cold storage to CA-storage, to ULO-storage. Since a few years, DCA-storage has been examined in various fruit systems. The threshold for oxygen partial pressure was reduced when a new method is applied. Three different possibilities to control “oxygen stress” exist. Measurement of chlorophyll fluorescence (DCA-CF), anaerobic metabolism products (DCA-Eth) or respiratory quotient (DCA-RQ) that are based on a dynamical variation of oxygen levels, depending on stress signal occurring in case of anaerobic metabolism. Maintaining low oxygen concentrations in storage will result in a minimum respiration is running rate. Therefore, the ripening process is slowed down, and this is required for a long storability and maintenance of fruit quality. The lowest oxygen limit (LOL) is the level that apples can be stored without damage, changes according to the cultivar, storage period, temperature, maturity stage, etc., ranging between 0.05 and 0.8kPa O₂. If, for example, RQ is higher 1.0 then the oxygen level is below the anaerobic compensation point, and anaerobic metabolism occurs. This might result in off-flavour due to production of alcoholic compounds like ethanol, acetaldehyde and ethyl acetate. The inhibition of ripening, either by DCA-storage based on chlorophyll fluorescence (DCA-CF) or by respiratory quotient (DCA-RQ) will maintain the firmness as well as green color in ‘Elstar’ and ‘Nicoter’ apples. The Incidence of physiological disorders like superficial scald is reduced in ‘Nicoter’ apples as well as fungal diseases in ‘Elstar’ apples, by storage under DCA. The storage of ‘Elstar’ and ‘Nicoter’ apples under DCA-RQ resulted in a rise of compounds related to off-flavours, like acetaldehyde, ethanol and ethyl acetate, but their concentrations were below the odour thresholds. However, storage under DCA-RQ resulted in a higher concentration of butyl acetate, 2-methylbutyl acetate and hexyl acetate, which contribute positively to the apple aroma. Storage of ‘Elstar’ and ‘Nicoter’ apples in DCA-RQ maintain better overall quality and volatile profile as compared to CA storage. Thus, the adoption of DCA technologies in commercial cold storage rooms would be beneficial for both storage facilities holders and consumers.