A general method for the instrumental assessment of the colour of tomato fruit during ripening

Abstract

The colour of subjectively-chosen tomato fruit of three contrasting cultivars at each of five stages of ripeness were measured on a tri-stimulus colour difference meter. The values were introduced into a formula previously developed for calculating objective limits for each ripening stage, but satisfactory separations were not achieved. When the colour components for areas on the side-walls of tomatoes were introduced into a revised formula, good discrimination was achieved between classes of fruit from fairly ripe to fully ripe. Similar measurements carried out on areas near the stylar scar and used with an alternative formula led to efficient separation of less ripe fruit into distinct classes. It is suggested that the revised formula can be applied to any cultivated tomato line except colour mutants.

Prediction of Changes in Color of Tomatoes during Ripening at Different Constant Temperatures

“…Predictive models were developed for change in tomato color during ripening as affected by ripening treatment, temperature and duration. Although previous models have been developed (Thorne and Alvarez, 1982;Hobson et al, 1983;Dixon and Hobson, 1984) this is the first report to predict color components (value, hue, chroma) and the first report adapting these models to sensory perception. The equations developed reasonably estimate marketability for vine-ripened tomatoes but do not provide adequate estimates for ethylene-treated tomatoes.…”

“…An index for assessing ripening stage during postharvest maturation has been developed by Hobson et al (1983) and later refined (Dixon and Hobson, 1984). Mathematical models have been reported to predict changes in the a/b ratio as affected by temperature (Thorne and Alvarez, 1982) and gaseous composition in a modified atmosphere (Yang and Chinnan, 1987) during tomato ripening.…”

Differences in the Rate of Coloration in Tomato Fruit

“…Color is one of the principal factors which determines the degree of consumer acceptance of tomatoes. Important changes take place during ripening in the chlorophyll (green), lycopene (red) and beta-carotene (orange) contents of the fruit (Davies and Hobson 1981) and various stages of development can be differentiated according to the external color (Hobson et al 1983; Dixon and Hobson 1984;Riquelme 1995).…”

Quality Inspection of Bakery Products Using a Color‐based Machine Vision System

“…The perception of food commonly starts from visual observation, and its acceptance relies on its color (Francis 1977). Visual inspection of brown-muffins has been carried out by instrumental assessment of the top surface color using a difference meter that can spectrally approximate eye function in terms of "L", "a" and "b" values (Dixon and Hobson 1984). The desirable color of brown-muffins, as indicated by L, a and b values, falls in the range of 47.55 to 42.27, -6.93 to -8.67 and 19.17 to 17.27 respectively (Adam 1996).…”