A model for firmness and low temperature-induced storage breakdown disorder of ‘Hayward’ kiwifruit in supply chain

Flesh softening and chilling injury related storage breakdown disorder (SBD) are the most important quality issues in the kiwifruit industry. This study was aimed at developing a mathematical model that could describe and predict evolution of storage breakdown disorder and firmness. A mechanistic modelling approach was adopted, with different concepts used to model the three phases of softening often observed in kiwifruit. The initial rapid softening phase was modelled as a function of starch breakdown, the slow softening phase was modelled as function of pectin degradation, while the final softening phase often characterised by tissue collapse, was modelled as a function of chilling injury related storage breakdown disorder. The model was calibrated using data collected from three seasons, across multiple maturity areas and subjected to different cooling and storage temperature regimes. 93 % of the total variance in the firmness data could be explained by the model. A mean absolute error of 0.2–2.2 % was obtained for SBD predictions. The developed model could be used by growers and postharvest managers to predict kiwifruit softening under different supply chain conditions.