Assessing the colour of tomato fruit during ripening

Abstract

The use of colour to separate tomatoes into groups at distinct stages of ripeness is usually a subjective procedure. In an attempt to reduce variability, tomatoes previously sorted by eye into five categories from mature green to full red were reassessed using a tristimulus colour difference meter. Various methods of presenting the samples to the machine for colour testing and of transforming the results were compared, and a formula was developed so that objective limits for each ripening stage could be calculated. In order to obtain matched samples of fruit at any particular stage of ripeness, the instrument can be programmed to reject fruit falling outside the appropriate limits. The colour components of tomatoes of several cultivars chosen subjectively to be at the same stage of ripeness (orange-red) were shown to be related to fruit firmness.

Chemotaxonomical Classification of Red Table Grapes based on Anthocyanin Profile and External Colour

“…Grape varieties (Vitis vinifera) can be classified according to the colour of their skins into the following groups: green-yellow, pink, red, red-grey, red-dark violet, red-black and blue-black (1). In order to determine the external colour of fruits numerically the CIELAB parameters (2) are commonly used (3)(4)(5)(6)(7)(8), as well as colour indices calculated from them (9)(10)(11)(12)(13)(14). Anthocyanin content is one of the parameters used to carry out chemotaxonomic studies in grapes and to study anthocyanin metabolism (15)(16)(17)(18)(19)(20)(21)(22)(23).…”

Comparison of Ripening Processes in Intact Tomato Fruit and Excised Pericarp Discs

“…1). This change in reflectance, when recorded on the L*a*b* axes, can be represented as a path through the a*b* color chart or as change along the a* axis (18).…”

“…Since ripening has been more thoroughly characterized in tomato pericarp than in any other fruit or tissue (4,14), a detailed comparison is possible. Previous studies have shown that, during normal ripening ofpericarp in intact tomato fruit, tissue color changes from green through orange to red (10,18), ethylene biosynthesis and respiration undergo a climacteric rise (35), tissues decrease in firmness (21), extractable activities of specific hydrolytic enzymes increase (7,17,19,28,34), and various fractions of the cell wall change in composition (15,16). In this article, these characteristics of ripening in whole fruit, as described here or by others, are compared with similar processes in excised pericarp discs.…”

Dependence between apparent color and extractable color in paprika

“…[12][13][14][15] We also applied the CCI ϭ 1000a*/L*b* index, reported for citrus, 16 and the COL ϭ 2000a*/L*C* index defined for tomato fruits. [17][18] Of these three indices proved, the highest correlation was with the COL index (Fig. 1), although it was lower than 0.84.…”