Postharvest softening of apple (Malus domestica) fruit:: a review

Postharvest softening of apple (Malus domestica (Borkh.)) fruit is a serious problem for growers in many countries, including New Zealand. To reduce this problem considerable research has been undertaken to determine the biological causes of softening so that this process can be managed or controlled more effectively. This review describes the pattern of softening for harvested apple fruit, and how it is influenced by different preharvest, at-harvest, and postharvest factors. Information is also given on the likely physiological and biochemical causes of apple softening, such as fruit anatomy and cell packing, modification of the cell wall and membranes, changes in cell turgor, and the role of ethylene and other growth regulators. Despite many softening studies, there is still a poor understanding of what causes firmness variation in the marketplace. Until this understanding is improved, apple producers will continue to struggle to meet market requirements for texture.