Comparison of softening-related changes during storage of 'Honeycrisp' apple, its parents, and 'delicious'

Many studies of apple (Malus xdomestica Borkh.) softening have been done using cultivars that eventually become mealy. We wanted to determine whether observations in these studies would be seen in a cultivar that maintains its crispness. In this paper, we compared the texture, ultrastructure, and some physiological parameters of Honeycrisp, an apple cultivar introduced in 1991 by the Minnesota Agricultural Experiment Station, with its parents and Delicious. Sensory evaluations and instrumental texture measurements showed that 'Honeycrisp' maintained a crisp texture from harvest through 6 months of cold storage, whereas its parents, 'Macoun' and 'Honeygold', softened over the same time period. Turgor potential, cell wall composition, and ultrastructural comparisons of the fruit were made. Cell turgor potentials of 'Honeycrisp' and 'Delicious' were similar and greater than those of 'Macoun' and 'Honeygold', and clearly correlated with firmness. There were no differences in cell wall neutral sugar composition, except for arabinose, which was not highly correlated with crispness. 'Honeycrisp' fruit maintained cell wall integrity after 6 months of storage, while cell walls of 'Macoun' and 'Honeygold' deteriorated. These data show that it is important to compare more than one cultivar when studying crispness. Honeycrisp is a cultivar that maintains its crispness through long storage without controlled atmosphere conditions. After 6 months of storage, this crispness can be attributed to a maintenance of high turgor potential and cell wall integrity.