Note. Visual and Instrumental Color Evaluation in Red Wines

Abstract

The color of 15 red wines from several wineries within the renowned wine-producing region Rioja (Northern Spain) was measured by spectrophotometric and spectroradiometric techniques and was visually assessed in a pair-comparison experiment by a panel of 10 experienced observers having normal color vision. Correlation between instrumental color measurements made by spectrophotometric and spectroradiometric techniques was very low, as expected from major differences in the experimental conditions employed (different illumination, path lengths and glass effects). Spectroradiometric measurements at the center of the wine sampler and at positions displaced 1 cm in the horizontal and vertical directions were quite different, mainly because of an increase of the lightness L*, the average color differences between them being high (3.5 and 2.6 CIELAB units, respectively). A 50% acceptance percentage resulted for a color difference of 2.8 CIELAB units, using a reference anchor-pair of wine samples with 4.0 CIELAB units. Thus, a value around 3.0 CIELAB units should be considered a preliminary estimate of the acceptable tolerance by the human eye for red wines poured in standard wine samplers.

Application of Differential Colorimetry To Evaluate Anthocyanin–Flavonol–Flavanol Ternary Copigmentation Interactions in Model Solutions

“…Specifically, MC+Q solutions showed significantly lower values of L* and hue but higher values of total color and C* ab than MC solution. In terms of detectable color variations 24 (Table 2), the highest color difference value was obtained between MC and MC+Q200 solutions (ΔE* ab = 20.6). The negative values of lightness and hue differences found among them (ΔL* = −14.2, Δh ab = −10.0°), but positive chroma difference (ΔC* ab = +13.3), means that MC +Q200 solutions had darker and more intense color with more bluish hue than MC solutions.…”

“…Also, in an attempt of understand the significance of the color changes, the absolute lightness, chroma, and hue differences (ΔL*, ΔC* ab , and Δh ab ) were calculated. According to Martinez et al, 24 ΔE* ab around 3 units indicates, approximately, color differences appreciable to the human eye (as an average observer). On the basis of this premise, the most perceptible color changes were produced when quercetin-3-β-D-glucoside was added to the MC solutions.…”

Impact of different wood chip species (oak, acacia and cherry) on evolution of individual anthocyanins, chromatic characteristics and antioxidant capacity in model wine solutions

“…4) showed that all mixture raised differences much higher than three CieLAB units. Thus, taking into account that E values of up to three CieLAB units indicates color differences appreciable to the human eyes [15], it could be affirmed that the contact between anthocyanin extract and wood chip extracts from different species led to color differences visually perceptible between in all model wine solutions. This result confirms the results already show for color intensity and the partial results obtained for CieLAB chromatic coordinates (Figs.…”

The influence of thermal treatments on the antioxidant activity and colour of chokeberry (aronia menocarpa) extract

“…Table 3 presents the overall difference in colour between the freshly prepared extract and those exposed to different thermal regimes and storage temperatures. For most treatments, except the ones involving temperatures of 80°C and 100°C, the colour was stable and was not modified significantly since the reported perceptibility threshold for CIELab colorimetric differences are ∆E * =0.8-1 (Gonnet, 2001) and ∆E * =3 (Martinez, Melgosa, Perez, Hita, & Negueruela, 2001). Higher ∆E * values were obtained for the extract exposed to 100°C for 2 min and the one kept at 25-30°C for two weeks, i.e.…”