A novel type of dynamic controlled atmosphere storage based on the respiratory quotient (RQ-DCA)

Abstract

A novel type of dynamic controlled atmosphere storage (RQ-DCA) was developed to control O2 and CO2 partial pressures in storage containers for apple fruit automatically, based on measurements of the stored fruit respiratory quotient (RQ). ‘Granny Smith’ apples were stored under RQ-DCA and the effect on fruit quality immediately after storage as well as during subsequent shelf life was investigated and compared to the effect of regular CA and regular CA storage with 1-MCP (SmartFreshSM) treatment. The RQ-DCA system managed to control O2 and CO2 partial pressures in the storage container in an autonomous way. During RQ-DCA storage, the RQ breakpoint was found to vary between 0.25kPa and 0.4kPa O2. However, difficulties to obtain a reliable RQ measurement were observed at very low oxygen levels due to reduced fruit respiration and when the pressure of the storage container increases due to increased atmosphere pressure due to leakiness of the storage container. Superficial scald was found to be controlled almost completely during storage with RQ-DCA and the effect remained visible during up to 14 days of shelf life. Magness-Taylor firmness and skin color (hue angle) were found to be significantly higher after RQ-DCA storage compared to conventional CA storage and were comparable to these of fruit stored with regular CA after 1-MCP treatment up to 7 days of shelf life at 18°C. In-fruit ethanol concentrations were found to be very low (<0.028gL−1), indicating the RQ-DCA system managed to store the fruit close to the anaerobic compensation point but the fruit metabolism did not shift from aerobic respiration to fermentation.