A mechanistic model to describe the effects of time, temperature and exogenous ethylene levels on softening of kiwifruit

• Kinetic model of kiwifruit softening was developed.
• Effect of exogenous ethylene on softening was modelled.
• Model could discriminate between batches of kiwifruit.
• Some at-harvest attributes show potential to predict batch-dependent parameter.

Early harvested kiwifruit (Actinidia deliciosa (A Chev) Liang et Ferguson cv ‘Hayward’), from 14 growers and two seasons were stored under a wide range of storage temperatures (0–10 °C) and exogenous ethylene levels (0–200 μL L−1) followed by an ethylene free shelf life period at 0–20 °C. Firmness levels were monitored using a non-destructive compression technique. A mechanistic model, based on a simplified representation of the physiology underlying fruit softening, explained 97% of the observed variation.The kinetic model parameters appeared to be generic for the 14 grower lines studied. Differences between the grower lines could be explained based on differences in the initial firmness levels and the initial amounts of active enzyme system present.The model was validated with independent experimental data on the softening of 70 batches of main harvest kiwifruit stored at 0 °C, with more than 99% of the variation explained for each of the 70 grower lines. A further validation was done using literature data on shipping of “Kiwistart” fruit under dynamic temperature and ethylene conditions.