Abstract
The concept of dynamic controlled atmosphere storage (DCA) involves the reduction of the oxygen level in the storage atmosphere to the anaerobic compensation point (ACP), dynamically adjusting the atmosphere composition during storage according to the fruit's physiological demand. For this purpose DCA requires a reliable method for the detection of the ACP, which is based on sensing the fruit response to hypoxic conditions. The objective of the present work was to evaluate the respiratory quotient (RQ) compared to chlorophyll fluorescence (Fα) as a control parameter for the O2 concentration in DCA. The research work was conducted with the apple cultivars 'Red Delicious' and 'Granny Smith', selected for their differing behaviour under low oxygen atmosphere conditions. The O2 level at the ACP and the corresponding RQ value were influenced by cultivar and growing season, but not by the maturity stage at harvest. The two cultivars exhibited a differing response to hypoxic conditions: whereas the anaerobic pathway of carbon dioxide production was pronounced in 'Red Delicious', the activation of this pathway was limited in 'Granny Smith'.