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Mouton et al. 2021. Comparison of CA storage technologies using O2 values and fruit quality. CAMA21 Conference poster.
Abstract. Increasingly, apples are stored under low oxygen conditions, such as controlled atmosphere (CA) and dynamically controlled atmosphere (DCA), to suppress ripening and associated quality degradation. The reported extent of acclimatisation to low oxygen during the storage period and the safety margins employed often differs with the storage technology and experimental design, making direct comparisons between technologies and different studies impossible, as there are no standardized measures to do so. This work compares four different storage technologies - DCA regulating on chlorophyll florescence (CF), DCA-CF + ethylene scrubbing, DCA regulating on respiratory quotient (RQ), and extreme low oxygen (XLO) with ethylene scrubbing. Granny Smith’ apples were stored for 283 days at -0.5 °C. Quality indices (firmness, titratable acidity (TA), total soluble solids (TSS) and TSS:TA) were assessed thereafter. The cumulative O2, cumulative O2 above a selected threshold (0.5 kPa, 0.7 kPa & 1.0 kPa O2), and the cumulative O2:CO2 ratio values were calculated and compared to fruit quality parameters. Lower O2 concentrations were associated with improved quality preservation. Flesh firmness, TA and TSS:TA, had logarithmic regression coefficients (R²) of >0.66 with cumulative O2values of the storage containers. A baseline of 0.5% O2 slightly improved the regression (R²>0.70). Considering time above each threshold value, hours above 1.0% O2 had the strongest R² value (>0.83), emphasizing the importance of O2concentrations <1.0% in quality preservation during storage. Given the importance of CO2 in CA to preserve fruit quality, the cumulative O2:CO2 ratio values were also considered, however, the R2 values were weak (R²<0.54) compared to cumulative O2. Shortcomings and advantages for the use of such a standard measure for comparisons are briefly discussed.
