Obtención de espectros metámeros con varios iluminantes para una muestra dada

Reciben el nombre de espectros metámeros aquellos que, aún siendo diferentes, proporcionan el mismo color bajo un iluminante y un observador dados. Sin embargo, si calculamos sus coordenadas colorimétricas con un iluminante diferente, éstas serán distintas y, en algunos casos, muy distintas. Un método de obtener espectros de reflectancia metámeros con otro dado consiste en reconstruir este espectro a partir de los vectores propios, obtenidos mediante PCA, de un amplio conjunto de espectros, como pueden ser las muestras del Atlas Munsell. En este trabajo se presenta un método para obtener espectros de reflectancia que sean metámeros bajo dos, o más, iluminantes. Este resultado es posible si conocemos los suficientes vectores propios de la base utilizada y los valores triestímulo del espectro original calculados con los respectivos iluminantes. Debido al método matemático usado en la obtención de los espectros, éstos son metámeros perfectos de la muestra original

Obtención de espectros metámeros que se cortan en longitudes de onda elegidas arbitrariamente

En trabajos anteriores hemos comprobado que se pueden utilizar técnicas de PCA sobre una amplia base de espectros de reflexión para obtener diferentes metámeros de un color dado para un observador e iluminante determinados. En ocasiones, puede resultar interesante que todos esos espectros tengan el mismo valor para una longitud de onda determinada. En este trabajo presentamos un método para obtener espectros metámeros que tengan el mismo valor de reflectancia en una o varias longitudes de onda determinadas

Pigment composition and color parameters of commercial Spanish red wine samples: Linkage to quality perception

Anthocyanins play a crucial role in wine color. Thus, their analysis results essential for evaluating their contribution to perceived color in wines, attribute directly linked to quality judgements. In this context, this study was aimed at: (1) defining the color space of a relative large number of commercial oaked Spanish red wines and (2) establishing a linkage between wine coloring, anthocyanic composition, and quality perception of this set of wines. Therefore, CIELab parameters (a10*, b10*, L10*), monomeric anthocyanin contents analyzed by HPLC with ultraviolet and mass detection, and polymeric pigment content estimated by a protein precipitation assay combined with bisulfite bleaching were evaluated in a total of 58 wine samples. Principal component analysis was performed on color variables, and their correlations were discussed. The results have evidenced the important role played by the pyranoanthocyanic compounds since they seem to be the main contributors to the red color of these aged wines, and they have been demonstrated not to increase their yellow nuances. On the other hand, results highlight that, regardless of the time of aging, wines presenting more red (higher values for a10* and for low molecular weighted anthocyanins) and lower yellow nuances (lower values for b10* and T) as well as a darker color (lower in L10* and higher in CI) are in general evaluated with higher quality scores by wine experts. © 2011 Springer-Verlag.The authors thank the Instituto de Estudios Riojano, and Consejería de Educación, Cultura y Deportes del Gobierno de La Rioja (FOMENTA 2008/07 project), MEC/FEDER (AGL2007-65139 project) for their financial support. MPSN thanks the University of La Rioja for her FPI grant.Peer Reviewe

Evolución del color y la composición antocianica de vinos tintos durante la etapa de envejecimiento en botella. Efecto de distintas concentraciones de oxígeno

Trabajo presentado en el XI Congreso Nacional del Color, celebrado en Orense del 19 al 22 de julio de 2016.Peer Reviewe

Evaluation of the impact of initial red wine composition on changes in color and anthocyanin content during bottle storage

Sixteen commercial red wines, selected to cover a different range of color and total polyphenols index (TPI), were stored at 25 °C during 6 months under controlled and different oxygen additions (0, 1.1, 3.1, 10.6 and 30.4 mg L) during the bottling process. Changes in color and the anthocyanic composition were evaluated using transmittance spectra and UPLC-MS-UV/Vis respectively. Results reveal a general pattern in the evolution of wines. However, different patterns of evolution related to initial wine composition, especially to TPI, were observed. Wines with higher TPI had a lower evolution, whereas wines with lower TPI showed a higher evolution and greater variability in behavior. In general, oxygen seemed to accelerate all changes observed during aging although the oxygen effect was more limited than the effect of the storage time. These results are relevant for wine experts and help explain the evolution of wine at the bottling stage.This work was funded by the Spanish Ministry of Economy and Competitiveness with the (Proyects AGL2010-22355 and AGL2014-59840) J.M.A. acknowledges the Government of Navarra for his predoctoral (FPI) fellowship and M.P.S.N. the Spanish Ministry of Economy and Competitiveness (M.E.C.) for her postdoctoral fellowship (Formación Posdoctoral 2013, former Juan de la Cierva).Peer Reviewe

Evolución del color y de la composición antociánica de vinos de crianza durante la etapa de envejecimiento en botella. Efecto de distintas concentraciones de oxígeno

Póster presentado en la XI Reunión Nacional de Óptica (Día de la Luz), celebrada en Salamanca del 1 al 4 de septiembre de 2015.Peer Reviewe

Understanding quality judgements of red wines by experts: Effect of evaluation condition

© 2015 Elsevier Ltd. The effect of evaluation condition on quality judgements of wine experts was evaluated. Quality perceived by wine experts was investigated under the assumption that this construct is built from multimodal sensory inputs. Twenty-one wine experts from Rioja (Spain) scored the intrinsic quality of 16 Spanish red wines under four conditions: (i) visual stimulation only, (ii) orthonasal olfaction alone, (iii) in-mouth sensations only (wearing a nose clip) and (iv) global tasting. Agreement among judges and the effect of evaluation condition were evaluated by principal component analysis (PCA) and ANOVA, respectively. In parallel, a trained panel described aroma, taste and in-mouth sensory properties such as astringency, global intensity and persistence. CIELab colour coordinates were also obtained. These descriptive data were submitted to regression analyses to explore their relationship with quality scores derived from the four evaluation conditions. Common mental representations of wine quality under visual, olfactory and global conditions were confirmed, while there was not a clear quality construct based exclusively on taste and mouthfeel properties. Wine taste and mouth-feel quality concept is suggested to be built only in combination with aroma and/or colour stimuli, and thus within a wine context. Global quality judgement integrated information provided by visual and olfactory cues, even if olfactory stimuli were suggested to have more importance on the construction of the global quality concept of wine experts. Significant interactions between wine and evaluation condition revealed significant differences in quality scores dependent on the stimuli received during tasting and on the wine judged. Sensory cues driving quality, especially visual and in-mouth properties varied depending on the evaluation condition, which suggested that global wine quality concept would be the result of the integration of perceptual and cognitive information rather than a collection of independent stimuli.This work was funded by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) with the AGL2010-22355-C02 and AGL2014-59840 projects. J.M.A. acknowledges the Government of Navarra for his predoctoral (FPI) fellowship and M.P.S.N. the Spanish Ministry of Economy and Competitiveness (MINECO) for her postdoctoral fellowship (Formación Posdoctoral 2013). L.A.A.E. acknowledges the continuous support of Diputación General de Aragón (T53) and European Social Fund.Peer Reviewe