Maturation of kiwifruit (Actinidia deliciosa cv. Hayward) from two orchards: differences in composition of the tissue zones

In a study on fruit maturation in kiwifruit (Actinidia deliciosa ( A Chev) Liang et Ferguson cv Hayward) fruit were harvested from orchards in two growing regions at fortnightly intervals from late March to early May. Soluble solids concentration (SCC) and flesh firmness of whole fruit were measured. Fruit samples were subdivided into three tissue zones: outer and inner cortex and core. Starch and the major sugars and acids in each zone were analysed. Other fruit were ripened with ethylene and evaluated for eating acceptability. There were major differences in carbohydrate and acid concentrations between the different tissue zones of the fruit, in particular in inositol, starch, and quinic and citric acid concentrations. The major differences between fruit from the two orchards were in total starch concentration and in the pattern of change in starch in the core. The citric/quinic ratio and malic/quinic ratio in the inner cortex and core also differed between fruit from the two orchards during the harvest period, although both followed the same trends with maturation. Both the sugar/starch and the sugar/acid ratios of the inner cortex differed between fruit from the two orchards at later stages of fruit maturation. The eating quality of the fruit from both orchards harvested in late March and early April at 4.5 and 4.8 % w/v SSC respectively was unacceptable, but all other fruit were found to be acceptable. Unacceptable fruit had a low flavour intensity, and a moderate level of off-flavours. The flesh texture was relatively mealy/grainy. The conditions under which fruit mature can cause differences both in the acid balance and the relative amounts of sugars and starch. The tissue zones also show different patterns of change during maturation. These differences may affect both the final eating quality of the fruit and the manner in which the fruit ripen after harvest.