Analysis of Tannins in Red Wine Using Multiple Methods: Correlation with Perceived Astringency

Abstract

The purpose of this study was to assess the relationship between astringency and tannin concentration in red wine using various analytical methods. Forty red wines were selected from a large commercial producer based on preliminary assessment of tannin variation and with selection intended to reflect potential variation in tannin amount. Tannin concentration was determined using previously published analytical methods, including absorption of light at 280 nm, reaction with 4-dimethylaminocinnamaldehyde, protein precipitation, phloroglucinolysis, and gel permeation chromatography. Results indicated that clear differences in tannin quantification existed in terms of the actual amount reported and in the relationship with perceived astringency in red wine. The analytical methods having the strongest correlations with perceived astringency were protein precipitation (r² = 0.82), phloroglucinolysis (r² = 0.73), and gel permeation chromatography (r² = 0.74). Given the equipment availability of most wineries, it was determined that protein precipitation was the most useful analytical method for astringency assessment. Because the protein precipitation method is similar to the physiological response to astringents, it could become an important in vitro tool for understanding how tannin structure modification leads to modification in astringency perception.