Assessing the colour of tomato fruit during ripening

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.