A fuzzy approach to the loss of green colour in lemon (Citrus lemon L. Burm. f.) rind during ripening

Abstract

This study describes the relationship between air temperature and the loss of greenness in lemon rind and the appearance of the typical yellow colour in the lemon varieties Eureka Frost on Citrus macrophylla rootstock. Lemon rind loses its green colour naturally in temperate climates when air temperatures fall. Greenness can be measured as the loss of “a” in reflection colorimetry. For each data recording session, while the mean air temperature is a certain fact, measurements of the coordinate a may show substantial variability despite the fact that they are made with an instrument of great accuracy. We propose a fuzzy methodology combining two elements: (a) possibilistic regression by means of trapezoidal fuzzy numbers, the estimate of which will provide a range of values that the variable in question could attain for a given mean temperature, and (b) the use of rules of the type if… then; this provides greater accuracy to the estimate because the degreening process only occurs between given temperatures. Until these temperatures fall below 11.5–16°C, degreening cannot be considered to have begun and the temperature will not influence the coordinate a. Finally, the aim of this kind of study is not to obtain one isolated estimate but rather a range of possible values that reflect reality.