Changes in firmness of the outer pericarp, inner pericarp, and core of Actinidia species during ripening

Abstract Firmness of Actinidia deliciosa (kiwifruit), A. chinensis , and A. arguta was measured using two methods. The first involved driving a 2 mm diameter probe radially into the fruit using a materials testing machine and recording the force‐distance curve as the probe passed through the different tissue zones. In the second method, puncture measurements (again using a 2 mm diameter probe) were made at a number of positions within tissues exposed by cutting equatorial or longitudinal slices of fruit (10 mm thick). The advantage of both methods is that they provide 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 Actinidia spp. generally undergo similar reductions in firmness, although the period between harvest and initiation of softening and the length of the softening period may vary. In one of the selections of A. chinensis , the fruit did not soften. During the consumption of kiwifruit, complex texture attributes will relate to the composition of all edible tissue zones (outer pericarp, inner pericarp, and core). Thus, we recommend that evaluation of firmness and softening of new Actinidia selections requires assessment of all tissue zones.