Dissecting the relationship of shrivel with firmness and weight loss in ‘Hayward’ kiwifruit

Shrivel detracts from kiwifruit quality. Water loss (approximate to weight loss (WL)) is considered to cause shrivel, although how much WL is required to cause shrivel may depend on fruit firmness. The association between WL, firmness and shrivel has been investigated in Actinidia chinensis var. deliciosa 'Hayward'. Fruit were stored at 0 degrees C until at similar to 6, 4, 2, and 1 kgf firmness (designated KG6, KG4, KG2 and KG1, respectively) when samples were transferred to chambers ventilated with dry air at 20 degrees C. WL was monitored until fruit shrivelled, at which time firmness was measured. All fruit had shrivelled by 14-16 days and most shrivelled fruit had WL >5.5%, and firmness <1.5 kgf, except in KG6 fruit (3.6 kgf), with no consistent association among or within treatments. WL rate decreased slightly with time at 20 degrees C for all treatments; KG6 fruit had the highest WL rate and KG1 fruit the lowest, suggesting a decrease in WL rate with time in storage, possibly associated with WL or softening. It is suggested that the association between WL and firmness in shrivel development is not simple. In firmer fruit, more WL may be required to cause distortion of rigid tissues, whereas in less rigid softer fruit, the effect of some degree of WL may be absorbed within the fruit before shrivel occurs. In both cases, the development of shrivel within the fruit depends on the rate of water loss and its re-equilibration within the fruit.