Microscopic observation of mealiness in apples: A quantitative approach

Mealiness is a quality characteristic that is used to describe fruit which is soft and which causes a dry feeling in the mouth during mastication. The purpose of this work was to visualise the difference between fresh and mealy apples and to quantify those differences. Three commercially important Belgian apple cultivars, 'Jonagold', 'Cox's Orange Pippin' and 'Boskoop' apples (Malus domestica Borkh.) were used in the experiments. Mealy apples were produced by holding apples at 20 degrees C and 95% RH for periods of time depending on the cultivar and the required mealiness level. Images were made with a light microscope. Cell parameters such as area and perimeter, and two roundness parameters were measured. 'Cox's Orange Pippin' and 'Boskoop' apples could be separated into the two groups: fresh and mealy, using the four calculated cell parameters. The number of broken and intact cells at the rupture surface of a fractured tissue sample after tensile loading was also calculated. After one week's storage of fruit in mealiness-inducing conditions, the amount of broken cells at the surface of a fractured sample was significantly lower than in fresh apples. (C) 1998 Elsevier Science B.V. All rights reserved.