A modelling approach to explain low apparent RQ-measurements of (D)CA stored Conference pear fruit
Recently, interest goes to the respiratory quotient (RQ), the ratio of the CO2 production rate and the O2 consumption rate of the fruit, as a bioresponse to detect low O2 stress to be used in dynamic controlled atmosphere storage (DCA). RQ shows a steep increase upon low O2 stress when fermentation becomes the dominant mode to metabolise sugars for providing energy. This makes RQ a good indicator for low O2 stress, which can be calculated by measuring the gas composition changes in the storage room. The technology has been shown to result in better post-storage quality for various apple cultivars. However, sometimes, low RQ values are observed during RQ-based DCA storage which remain poorly understood until now. In this work, the relation between non-steady-state gas conditions of the fruit-Hstorage environment system and RQ-values measured in the headspace of the storage environment is investigated. Dedicated jar experiments were conducted to evaluate the effect of non-equilibrium gas conditions on measured rates of O2-consumption and CO2-production by fruit respiration. A gas transport model was developed. The experimental scenarios were simulated and results were compared to the experimentally obtained measurements. The results indicate that non-steady-state between fruit-environment gas conditions has a significant effect on measured CO2 production rates, while little effect on measured O2 consumption rates was observed. An apparent measured RQ of 0.65 was related to an actual RQ-value of 1.0 inside the fruit cells by the model.
Bessemans, N., Verlinden, B.E., Janssens, M., Verboven, P., Hertog, M.L.A.T.M. and Nicolaï, B.M. (2021). A modelling approach to explain low apparent RQ-measurements of (D)CA stored Conference pear fruit. Acta Hortic. 1311, 249-256
dynamic controlled atmosphere, non-equilibrium, respiratory quotient, gas exchange, Pyrus communis L