CHANGES IN FIRMNESS OF THE OUTER PERICARP, INNER PERICARP, AND CORE OF ACTINIDIA SPECIES DURING RIPENING

Firmness of Actinidia deliciosa (kiwifruit), A. chinensis, and A. argu ta was measured using two methods. The first involved driving a 2 mm d iameter probe radially into the fruit using a materials testing machin e and recording the force-distance curve as the probe passed through t he different tissue zones. In the second method, puncture measurements (again using a 2 mm diameter probe) were made at a number of position s within tissues exposed by cutting equatorial or longitudinal slices of fruit (10 mm thick). The advantage of both methods is that they pro vide information on the firmness of all tissue zones within the flesh. By comparison, conventional penetrometer measurements mainly reflect the firmness of the outer pericarp. The results indicate that Actinidi a spp. generally undergo similar reductions in firmness, although the period between harvest and initiation of softening and the length of t he softening period may vary. In one of the selections of A. chinensis , the fruit did not soften. During the consumption of kiwifruit, compl ex texture attributes will relate to the composition of all edible tis sue zones (outer pericarp, inner pericarp, and core). Thus, we recomme nd that evaluation of firmness and softening of new Actinidia selectio ns requires assessment of all tissue zones.