Impact of adding white pomace to red grapes on the phenolic composition and color stability of Syrah wines from a warm climate.

The influence of the fermentative addition of Pedro Ximenez grape pomace (PXGP, white variety) on the phenolic composition and color of Syrah red wines from a warm climate was studied. Changes on phenolic composition (HPLC), copigmentation/polymerization (spectrophotometry), and color (tristimulus colorimetry) allowed differences among the maceration treatments to be established. PXGP additions at the rates studied increased the extraction of total phenolics, phenolic acids, and monomeric flavanols. However, the effect on the anthocyanins, copigmentation, and polymerization depended on the doses applied, with important consequences on the color. PXGP addition at 10% led to wines with higher polymerization, more stable colors, and bluish hues. in contrast, perceptibly lighter and less intense wines were obtained with PXGP addition at 20%. Thus, the use of white grape byproducts as wine additives at appropriate levels (10% w/w) could improve the phenolic potential of red young wines from a warm climate, contributing to preserve their color characteristic.

Influence of prefermentative cold maceration on the color and anthocyanic copigmentation of organic Tempranillo wines elaborated in a warm climate.

The stabilization of red wine color by the copigmentation phenomenon is a crucial process that does not always proceed favorably under natural conditions during the first stages of vinification. The impact of the prefermentative cold maceration technique on the phenolic composition and magnitude of the copigmentation level of organic Tempranillo wines elaborated in a warm climate have been studied as an enological alternative to the traditional maceration for obtaining highly colored wines. Tristimulus colorimetry was applied to study the color of wines during vinification, and a high-performance liquid chromatography (HPLC) procedure was used for the analysis of phenolic compounds. Spectrophotometric and colorimetric analyses were also performed to evaluate the copigmentation level of the wines. Significant chemical and color differences were found depending on the maceration technique applied. Prefermentative cold macerated wines were richer in those compounds accounting directly for the color of red wine (anthocyanins) and those involved in anthocyanin stabilization through copigmentation reactions (phenols), which was in accordance with the higher copigmentation degree and darker, more saturated and vivid bluish colors. The evaluation of the copigmentation based on colorimetric parameters in the CIELAB color space showed that prefermentative cold maceration caused greater effectiveness of copigmentation than traditional maceration since it induces more important and hence more easily perceptible color changes.