Tannins enological

Sami-Manchado, P. et al.. Analysis and characterization of wine condensed tannins precipitated by proteins used as fining agent in enology. Am. J. Enol. Viticult., 50, 81, 1999. 

New enological technologies aim to lower volatile acidity, enhance sugar content in must in cool climates and vice versa reduce the alcohol content of wines from hot climates, modify pH, cations, anions and acidity to achieve tartrate stability, complement traditional ageing in oak barrels with the use of small oak wood particles and most recently, extract phenolic compounds by a countercurrent chromatography process from wine to diminish or enrich tannins in red wines. 

In conclusion, the characteristic properties of tannins (especially their enological properties) are related to their ability to bind protein—a quality directly related to the polymerization of tannin molecules which arise from two to 10 simple flavan molecules with molecular weights... 

The most commonly used fining agents in the wine industry are bentonites (mainly containing montmorillonite) and proteins associated to tannins or a mineral agent. Gelatin has also been used in enology since the nineteenth century, but due to the crisis of the mad cow disease in 1999, plant proteins have widely been experimented and are now more and more used on an industrial scale. For this reason, this chapter will essentially focus on bentonite as well as plant proteins. 

Sanz, M.L., Martmez-Castro, L, Moreno-Arribas M.V. (2008) Identification of the origin of commercial enological tannins by the analysis of monosaccharides and polyalcohols. Food Chem., Ill, 778-783. 

Bautista-Ortin, A. B., Martinez-Cutillas, A., Ros-Garcia, J. M., Lopez-Roca, J. M., Gomez-Plaza, E. (2005). Improving colour extraction and stabdity in red wines the use of maceration enzymes and enological tannins./nt. /. Food Sci. Technol., 40, 867-878. 

Practices that increase formation of aldehydes, such as microoxygenation, promote polymerization of anthocyanins and catechins or tannins, thereby improving color intensity and stability. The formation of yellow and red pigments from colorless compounds is a very recent concept in enology since... 

Figure 1. Parallel Determination of Tannins and Polymeric Pigments. The procedure shown in the rectangle (left) is a Somers assay performed at pH 4.9 and provides a measure of total pigments and total polymeric pigments (LPP + SPP) at that pH. The procedure shown in the polygon (right) is the Hagerman Butler assay for tannin. 2003 American Society for Enology and Viticulture.

Figure 2. Absence of a correlation between the background absorbance in the tannin assay and the amount of polymeric pigment in 12 wines as determined in the standard Somers assay at wine pH. The analysis was performed twice about eight months apart. 2003 American Society for Enology and Viticulture.

The addition of enological tannins only eliminates part of the proteins, and the new tannin-protein complexes in the wine are generally more heat sensitive than the original proteins. 

Hydrolyzable tannins are not naturally found in grapes. On the other hand, they are the main commercial tannins legally authorized as wine additives. Ellagic acid in wine originates either from wooden containers or from the addition of enological tannins. On the other hand, gallic acid from the skins and seeds is always present in wine. 

Secondly, colloids may be adsorbed. For example, enological charcoal removes most colloids from solntions. In wine, it acts on tannins, coloring matter and proteins. Bentonite fixes proteins by the same mechanism. 

As compared to normal standards, the recommendations in the enological codex specify gelatin s nitrogen content (above 14% by dry weight) and precipitation by tannin number. This number represents the quantity of tannins necessary to precipitate all of the gelatin . It is not very significant, in view of the diverse structures of tannins and the non-stoichiometric nature of tannin-protein reactions (Section 10.5.1). 

The official definition of tannin (acidum tannicum) given by the Enological Codex is as follows ... 

Enological tannin is whitish-yeUow or bnff-colored, with an astringent taste. It is solnble in water, and partially solnble in ethanol, glycerol. 

Table 10.5. Phenolic composition of some commercial enological tannins...

Tannins and anthocyanins are key wine component groups. Since the skins and seeds contain the most of the phenolics, red wine is a whole berry extract. In addition, because of the significant sensory effects of these substances on bitterness and astringency, they are controlled by winemakers. The methods of control involve the manipulation of extraction as well as fining with protein to precipitate and remove tannin from finished wine technological enological process as nano- or ultrafiltration is now seeing some use. While many studies have... 

Puech, J.-L., Feuillat, F. Mosedale, J.R. (1999a). The tannins of oak heartwood structure, properties and their influence on wine flavor. American Journal of Enology and Viticulture, 50, 469 78. 

The action of phenolic compounds on lactic acid bacteria growth remains relatively nnknown. Past results have shown that polyphenols tested alone or in a mixture had an inhibitory effect. Saraiva (1983) noticed, on the contrary, that gallic acid stimulates yeasts and lactic acid bacteria. Conversely, different phenolic acids (coumaric, pro-tocatechic acid, etc.) and condensed anthocyanins inhibited them. Enological tannins were found to have an antibacterial effect (Ribdreau-Gayon et al 1975). The effect of phenolic compounds on lactic acid bacteria growth remains unclear. 

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