The color of wine: a historical perspective. II. Trichromatic methods

The trichromatic theory was applied to wines at the end of the 1930s. Trichromatic co‐ordinates, dominant wavelength, purity and luminance were determined. The Munsell system and the Lovibond method, which had industrial applicability, were compared with the simplified methods proposed by the L'office Internationale de la Vigne et du Vin (OIV). These methods are official in Spanish food regulations on wine analysis. The CIE recommendations, through the weighted ordinate method, set up the colorimetric parameters for wines, such as hue, lightness, purity or saturation, differences of color, perceptibility. Lately, attempts have been made to correlate the chromatic properties of wines with composition, origin, aging and sensory evaluation. Some authors have studied the reliability of the OIV methods versus the more rigid recent CIE methods. Improved formulae for the computation of dominant wavelength and outstanding correlations among sensorial scores, chromatic parameters and anthocyanins (polyphenols) content of wines have been established

The color of wine - a historical-perspective .I. Spectral evaluations

In the 1930s trade transactions required that the color of wine be more rigidly specified. The wine‐colorimeter was useful with this purpose. Intensity of color was the first property to be considered. From the beginning of this century visual comparisons of wines with standard mixtures of dyes or colored substances (potassium permanganate and dichromate) were made. Later photometric studies (absorption curves) were developed. Maxima and minima in the absorption curve were defined, as well as their relationships. Recently, it has been shown that absorbance values at given wavelengths and luminosity are well correlated

Estimation of Total Phenols, Flavanols and Extractability of Phenolic Compounds in Grape Seeds Using Vibrational Spectroscopy and Chemometric Tools

Near infrared hyperspectral data were collected for 200 Syrah and Tempranillo grape seed samples. Next, a sample selection was carried out and the phenolic content of these samples was determined. Then, quantitative (modified partial least square regressions) and qualitative (K-means and lineal discriminant analyses) chemometric tools were applied to obtain the best models for predicting the reference parameters. Quantitative models developed for the prediction of total phenolic and flavanolic contents have been successfully developed with standard errors of prediction (SEP) in external validation similar to those previously reported. For these parameters, SEPs were respectively, 11.23 mg g−1 of grape seed, expressed as gallic acid equivalents and 4.85 mg g−1 of grape seed, expressed as catechin equivalents. The application of these models to the whole sample set (selected and non-selected samples) has allowed knowing the distributions of total phenolic and flavanolic contents in this set. Moreover, a discriminant function has been calculated and applied to know the phenolic extractability level of the samples. On average, this discrimination function has allowed a 76.92% of samples correctly classified according their extractability level. In this way, the bases for the control of grape seeds phenolic state from their near infrared spectra have been stablished.España MINECO AGL2017-84793-C2España, Universidad de Sevilla VPPI-II.2, VPPI-II.

Valorization of American Barrel-Shoot Wastes: Effect of Post Fermentative Addition and Readdition on Phenolic Composition and Chromatic Quality of Syrah Red Wines

The influence of post fermentative addition of American barrel-shoot wastes on phenolic composition and chromatic quality of Syrah red wines has been evaluated as an environmentally sustainable alternative to the conventional winemaking for avoiding the common color loss of red wines elaborated in warm climates. American oak wood byproducts added were previously classified by hyperspectral image analysis according to the amount of phenolic compounds transferred to the extraction media. After that, wines were elaborated under different maceration conditions by applying only one proportion of wood (12 g L−1) and two different maceration procedures (simple and double addition) and were compared with a traditionally macerated Syrah red wine (CW, no wood addition). Results proved the effectiveness of the moderate postfermentative addition of oak wood byproducts to stabilize the color of wines and to provoke lower color modification along the time, producing color wines chromatically more stable for a better aging. In the case of double addition, the adsorption of the pigments during the maceration presents a stronger effect on the color than copigmentation and polymerization by cause of the copigments extracted from the woodEspaña, Ministerio de Economía y Competitividad AGL2017-84793-C

Aplicación de técnicas de imagen para la evaluación de la madurez fenólica de semillas de uva

Quality of wine depends fundamentally on the condition of the components of grapes at the moment of harvest. In this respect, their seeds directly affect to structure, astringency, stability, and indirectly to colour of wine. In this work, the grape seeds have been evaluated by techniques of image analysis. In all cases, the methodology was developed trying to entail the minimum sample preparation and maximum quickness of the method, and as far as possible, substitute the chemical analysis that usually involves long and tedious processes that hamper monitoring of ripening in a rapid way. The proposed methodology for measuring and evaluating colour and near infrared spectrum has yielded satisfactory results for estimating the ripening of grape seeds, and it has been useful for establishing stages of ripeness from their optical features.La calidad del vino depende en gran medida del estado en que se encuentren los diferentes componentes de la uva en el momento de la recolección y, en este sentido, las semillas afectan directamente a su astringencia, así como a la estructura y estabilidad del color del vino. En el presente trabajo se han evaluado semillas de uva de diferentes variedades aplicando distintas técnicas de análisis de imagen. En todos los casos se han desarrollado metodologías que implican la mínima preparación de muestra y la máxima rapidez del método, con el objeto de poder sustituir, en la medida de la posible, el análisis químico, que suele suponer largos y tediosos procesos que impiden un seguimiento rápido de la maduración. La metodología propuesta para la medición y evaluación del color y el espectro infrarrojo cercano ha dado resultados satisfactorios en la estimación del estado de madurez de las semillas de uva, y ha sido útil para establecer etapas de maduración a partir de sus propiedades ópticas.Ministerio de Economía y Competitividad AGL2008-05569-C02-02, AGL2011-30254-C02-02 y AGL2014-58486-C2-2-

Comparative study on the use of anthocyanin profile, color image analysis and near-infrared hyperspectral imaging as tools to discriminate between four autochthonous red grape cultivars from la Rioja (Spain)

Three independent methodologies were investigated to achieve the differentiation of red grapes from different grape varieties (Garnacha, Graciano, Mazuelo and Tempranillo) collected from five vineyards located in the D.O.Ca. Rioja. Anthocyanin chromatographic analysis, color image analysis and near infrared hyperspectral imaging were carried out for the grapes. Then, a Stepwise Linear Discriminant Analysis (SLDA) was developed for each data set in order to discriminate grapes according to their grape variety. As a result, using anthocyanin profile, color image analysis and near infrared hyperspectral imaging respectively, 88%, 54% and 100% of the samples were correctly classified in the internal validation process and 86%, 52% and 86% were correctly classified in the leave-one-out cross-validation proces

Potential use of new Colombian sources of betalains. Colorimetric study of red prickly pear (Opuntia dillenii) extracts under different technological conditions

A new source of betalains to be used as natural colorant (Opuntia dillenii) has been studied. The stability of O.dillenii extracts in different pHs and temperatures over time has been scrutinized. Our attention was focused on differential tristimulus colorimetry and betalain content related to the color, not previously conducted in con- junction in that raw material. On the basis of the results, cold storage conditions (4 °C) were optimal to maintain as possible the initial red color (hab), lightness (L*) and betalain content of the O. dillenii extracts, regardless of pH. Highly-acidic extracts (pH 4) manifested a significantly (p b 0.05) lower colorant intensity (C*ab) and betalain concentration (around 25% and 35%, respectively), with a clearer tendency toward yellowish tonalities (values of hab from 45° to 90°) over time. Furthermore, visually perceptible color changes (ΔE*ab N 3) were induced among very acid (pH 4) and low-acidic (pH 5 and 6) extracts at each temperature

The color of olive oils: The pigments and their likely health benefits and visual and instrumental methods of analysis

The color of olive oils, and of foods in general, can influence consumer choices to a large extent and can be related to the processing treatments they have undergone. Olive oil color is due to 2 types of pigments, chlorophylls and carotenoids, which are attracting the attention of the scientific community due to the probable health benefits they can provide. Appropriate methodologies for the meaningful definition of the color of olive oil are there-fore necessary for various reasons. In this review, we discuss the importance of olive oil color and the applicable legislation and regulation, including sections devoted to the pigments accounting for the growing importance as likely health-promoting substances. Furthermore, we review in depth the different approaches (visual and instrumental methods) used for color measurements in the last 50 y. Instrumental methods have been shown to be highly appropriate for objective assessments and also for the rapid determination of the pigments

Tristimulus weight functions to calculate musts color coordinates from 10-nm bandwidth spectral data

Color measurement of red musts is affected by errors due to the instrument architecture. The influence of bandwidth in color coordinates errors is studied and a set of weighting functions for the color coordinates calculation, from 10 nm spectral data, is proposed