Colour Measurement of Foods

Colour profile analysis of Port wines by various instrumental and visual methods

“…The visual assessment results showed a better colour distinction at shallower depths (2.0, 3.2 and 4.0 mm) for both styles of Port wine (ruby and tawny). The relationship between measured and visually perceived colour has previously been described in the literature, for different wine types at different depths 1,14,19 In this work we obtained good linear correlations between the H* parameter and the perceived hue of ruby-style Port wines, particularly at higher depths, despite a high dispersion of the visual scores also being observed. In tawny-style wines, a curved pattern was obtained with increasing depth which could be partially related to contrast effects previously described in the literature such as the Bezold-Brücke shift or the Abney effect.…”

“…The visual assessment results showed a better colour distinction at shallower depths (2.0, 3.2 and 4.0 mm) for both styles of Port wine (ruby and tawny). The relationship between measured and visually perceived colour has previously been described in the literature, for different wine types at different depths…”

“…Being a translucent matrix, the colour of a wine is expected to be affected by the quality and direction of illumination, viewing geometry and the inclusion/exclusion of specular component. 1 In the case of colorimetric measurements, where the reflected radiation is measured at an angle near 0 ∘ (with the specular component included), some translucency errors can occur by light trapping, meaning that not all light reaches the detector. On the other hand, in the spectrophotometric method, a monochromatic beam of light passes (and is transmitted) through the sample, minimizing the effect of light trapping.…”

“…On the other hand, in the spectrophotometric method, a monochromatic beam of light passes (and is transmitted) through the sample, minimizing the effect of light trapping. 1 Since in the spectrophotometric method the results are extrapolated (using the Beer-Lambert-Bouguer law) from a path-length of 1.0 mm to higher path-lengths (2.0, 3.2, 4.0, 4.8 and 6.0 mm), possible refraction or reflection effects at these higher path-lengths are not taken into consideration by this approach. On the other hand, the colorimeter used (Konica Minolta CR-400) is designed so that the sample is illuminated almost equally from all directions (measuring the vertically reflected radiation from the wine sample), which creates more realistic illumination conditions, comparing to visual assessment of translucent liquids such as wine.…”

“…From a sensorial perspective, colour is the visual perception of the refracted or reflected radiation from an object under a specific light source. 1 Wine colour is normally assessed visually in a standard glass tilted at an approximate 45 ∘ angle, where the wine adopts an oval shape. Since wine is a translucent product, its colour perception depends on the observed depth in the glass.…”