Sample size to evaluate the flesh firmness and epidermis color in peach and apple

Abstract

The aim of this study was to determine the sample size required to asses flesh firmness and epidermis background color of ‘Eragil’ peaches and ‘Royal Gala’ apples. Two experiments were carried, one with peaches and another one with apples placed inside 0.23 m3 minichambers. The peaches were stored for eight weeks at -0.5 ºC, and then for four additional days at 20 °C, next eight kinds of storage where assessed (refrigerated, controlled atmosphere with different concentrations of O2 and CO2 and with or without ethylene absorption). The apples were kept at a refrigerated storage for four months at 0.5 °C, and then for seven additional days at 20 °C, the treatments were composed by doses of 1-methylcyclopropene combined with types of wooden planks. The number of assessed fruits ranged from 30 to 57 for peaches and from 78 to 101 for apples. In each fruit the flesh firmness was measured by a manual penetrometer and the background color of the epidermis (brightness, intensity and color tone) by an electronic colorimeter. Thereafter, the size sample needed to estimate to flesh firmness and the background color of the epidermis was determinate.  In peaches, 121 fruit are enough to estimate the average of the flesh firmness and epidermis background color with an estimation error of 5% on the average in a controlled atmosphere and 10% in cold storage. In apples, 24 fruits are enough to estimate the average of the flesh firmness and epidermis background color, with an estimation error of 5% on the average.