Textural changes in ‘Hayward’ kiwifruit during and after storage in controlled atmospheres

Abstract

Storage of kiwifruit in controlled atmospheres (CA) is a common practice to extend the marketing window. An investigation into the softening of CA-stored ‘Hayward’ kiwifruit is described. Fruit softening during and after CA was recorded by standard penetrometer and also for specific tissue zones: outer pericarp, inner pericarp and core. In addition, when making standard penetrometer measurements, the degree of displacement of the fruit surface prior to penetration was recorded. The data have been used to describe the rate of post-CA softening and the relative softening of the outer pericarp, inner pericarp and core tissue zones.Results confirmed the benefit of CA storage in maintaining fruit firmness. Firmness retention in a 5% CO2 CA was better than in a 2% CO2 CA. The effect of 5% CO2 was maintained for a couple of weeks after transfer from CA- to air-storage. The rate of softening on transfer from CA- to air-storage increased to a rate equivalent to that of a fruit of similar firmness stored in air. The softening patterns of the inner and outer pericarp tissues were exponential whilst the core was closer to linear. Whilst the softening of all tissue zones was slowed by CA, the outer pericarp appeared to be slowed to a greater extent than the inner pericarp. A consequence of the differential effect of CA on the two pericarp tissue zones was that after CA storage the inner pericarp had become relatively softer than the outer pericarp when compared with air-stored fruit at the same fruit firmness value. This may account for the observed greater deformation of the fruit before tissue rupture for CA-stored fruit than air-stored fruit at the same firmness when making a penetrometer measurement.