Hydrolysable tannins can react among themselves to form large polymeric complexes. Gallotannins produce a sugar molecule and gallic acid, whilst ellagitannins yield the same reaction products and additionally a molecule of ellagic acid (Smeriglio et al., 2017). Hydrolysable tannins are divided into gallotannins and ellagitannins, which yield different products under acid hydrolysis. On the other hand, hydrolysable tannins are molecules that are easily decomposed in the presence of a weak acid and/or high temperatures to yield pyrogallol. Condensed tannins originate in the grape berry, where they are found both in skin and seeds (Harbertson et al., 2002). Tannins, which are known to be the main contributors to astringency in red wine, are secondary metabolites of plants and are usually classified as condensed tannins or proanthocyanidins, and hydrolysable tannins (Sarneckis et al., 2006).Ĭondensed tannins are flavan-3-ol polymers composed by different isomeric forms of catechin and gallocatechin (Aron & Kennedy, 2008 Kuhnle, 2018) and they are usually linked by C4-C8 and C4-C6 bonds giving rise to varying degrees of polymerization (Pascal et al., 2007 Vidal et al., 2004), expressed as mean degree of polymerization (mdP). Within the multiple parameters that are used to characterize red wines, astringency is one of the factors that is important in assessing their quality (Brossard et al., 2016 García-Estévez et al., 2017). Keywords: Tannin content, Bate Smith, acid hydrolysis, Adams Harbertson, BSA tannin assay, methyl cellulose precipitation, astringency, red wines The purpose of this article is to present the main advantages and disadvantages of the three spectrophotometric methods acid hydrolysis, BSA assay and MCP methods for tannin determination in red wine, in order to review their efficacy, group of tannins each method can determine, and their suitability for astringency prediction. These methods differ on the principle upon which they are based, as well as on the kind of tannin that they can determine. This article focuses on the three methods most frequently used by the wine industry: Bate Smith or acid hydrolysis method, Adams Harbertson assay or BSA tannin assay, and methylcellulose precipitation (MCP) method. These molecules in wine can be determined and analysed by spectrophotometric, analytical and recently electrochemical methodologies. The astringent sensation inside the mouth is caused by a group of molecules called tannins. Brossard *ĭepartment of Fruit Production and Enology, School of Agricultural and Forest Sciences, Pontificia Universidad Católica de ChileĪstringency is an important sensory attribute that influences red wine quality. A Review of Tannin Determination Methods Using Spectro-photometric Detection in Red Wines and Their Ability to Predict AstringencyĬ.
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