Comparison of analytical methods for measuring proanthocyanidins in wines and their relationship with perceived astringency

Abstract

Artículo de publicación ISIThe concentration of proanthocyanidins from twenty red wines from cv. Cabernet Sauvignon, five ros e wines from cv. Cabernet Sauvignon and five white wines from cv. Sauvignon Blanc was quantified using four analytical methodologies, and their relationship with the perceived astringency was investigated. Proanthocyanidin concentrations were determined by a methylcellulose precipitation assay, a protein precipitation assay and two colourimetric methods (Bate-Smith and vanillin assay). The four methodologies showed high repeatability but differed widely in proanthocyanidin concentrations. The methylcellulose and protein precipitation assays could not quantify proanthocyanidins in ros e and white wines. The protein precipitation assay gave the lowest concentration of proanthocyanidins in all of the red wines. The methylcellulose precipitation assay (r = 0.7725; r2 = 0.59) and the protein precipitation assay (r = 0.6828; r2 = 0.47) showed a strong correlation with the perceived astringency compared with the colourimetric methods. The strong correlation of the methylcellulose precipitation method with the perceived astringency could be a useful tool to estimate red wine astringency

The Role of UV-Visible Spectroscopy for Phenolic Compounds Quantification in Winemaking

“…On the other hand, the comparison of both precipitations based methods has shown that MCP tannin values are on average three time higher than those found for BSA. However, a strong correlation (0.8) between the values obtained with the two methods has also been reported [42], whereas no correlation was observed between these two methods and the tannin content obtained with the acid hydrolysis method [37]. Finally, despite the differences in absolute values, attributable to the differences in both procedures, it has also been stated that both precipitants (BSA and MCP) precipitate the same amount of tannins when tested under the same conditions [39,43].…”

“…The total tannin content is in this case estimated as epicatechin equivalents. In addition, one of the main benefits of precipitation based methods is that a theoretic positive correlation with astringency intensity is foreseen [37][38][39]. The hypothesis is based on the assumption that the method simulates the phenomena that naturally occurs in wine when it becomes in contact with the salivary proteins.…”

“…The accuracy of the method is based on obtaining the appropriate wine dilution as concentrated or very diluted samples tend to underestimate the tannin content. The BSA tannin assay, as part of the precipitation based methods for tannin analysis, has also been found to positively correlate with astringency intensities given by sensorial evaluation [37][38][39]. The total tannin content is in this assay calculated as catechin equivalents.…”

Flavan‐3‐ols and Condensed Tannin

“…• Classic tannin analyses rely on condensation reactions with aldehydes such as vanillin to yield a colored product [26]. These approaches will detect monomers as well, and are not often reported for wine analysis.…”

New Approaches to Tannin Characterization

“…Following precipitation, the phenolic content of the pellet or supernatant can be measured. These precipitation methods can achieve very high correlations between "astringency intensity" and "tannin" (r 2 > 0.8), likely because they mimic reactions that would occur between tannins and lubricating salivary proteins in the mouth [7]. …”