Enhancing the color and astringency of red wines through white grape seeds addition: Repurposing wine production byproducts.

The clear juice fermentation technique for white wines suggests that white grape seeds, rich in flavan-3-ols and proanthocyanidins, are not effectively utilized in the winemaking process. This study incorporated 'Gewürztraminer' grape seeds into 'Cabernet Sauvignon' must before cold soak to investigate how the resultant red wines' phenolic compound profiles, color, and astringency were affected. The results showed that adding seeds primarily inhibited the leaching of flavan-3-ols from both skins and seeds. A significant increase in the levels of flavan-3-ols, tannins, and phenolic acids, as well as direct and aldehyde-bridged flavan-3-ol-anthocyanin polymers, were observed in the wines with additional seeds. This led to the improvement in the wine' red hue and its resistance to SO2 bleaching. Furthermore, the wine added with seeds exhibited stronger astringency compared to those without. The findings provide a promising winemaking strategy to improve color stability and intensify the astringency of red wines through the utilization of grape seeds.

Artificial saliva precipitation index (ASPI): An efficient evaluation method of wine astringency.

Astringency is one of the most important organoleptic characteristics of red wines, and its intensity evaluation method has been the focus of research in recent years. An artificial saliva system was developed to establish an accurate and reliable evaluation method for the astringency intensity of dry red wines based on saliva precipitation index (SPI). To achieve this, five key protein families, which presented high reactivities and sensitivities in protein-tannin binding reactions, were selected from human whole saliva. The concentrations of the five proteins (proline-rich protein, α-amylase, lactoferrin, lysozyme, and albumin) and pH were optimized using response surface methodology based on the human salivary conditions to simulate the real salivary environment. The artificial saliva precipitation index method was applied to 60 commercial dry red wines and it exhibited a high correlation (CoefASPI = 0.94) with the sensory scores, indicating better performance than the traditional SPI method and other analytical approaches.

Blending strategies for wine color modification â : Color improvement by blending wines of different phenolic profiles testified under extreme oxygen exposures.

Limited oxygenation and over-oxidation experiments were designed to compare the phenolic and chromatic characters of base wines Cabernet Franc (CF), Cabernet Sauvignon (CS), and their counterparts that blended with modifier wines Marselan (MA) and Petit Verdot (PV). In both limited oxygenation and over-oxidation conditions, all blend wines generally contained higher C*ab, a* and Red%, and lower hab, b* and Yellow% than their base wine counterparts, because MA contributed flavonols (copigments) and anthocyanins, and PV contributed flavanols (anthocyanin derived pigments precursors). Chromatic changes that can be perceived by human eye (ΔE*ab) in CF based blend wines were more obvious than that of CS based blend wines, which indicate that base wine with lower phenolic concentrations and weak phenolic profiles (CF) might be more prone to be chromatically modified than base wine with higher phenolic concentrations and distinct phenolic profiles (CS). Chemical influences of different blending strategies on anthocyanin derivatives' formations were depending on phenolic profiles of the modifier wines and base wines, and also on the oxygen exposure. The results suggest that the chromatic improvement of base wines could be realized by blending modifier wines under different oxygen exposures.