Tannins grape skin extract

Grape skin extract (enocianina) is a purplish red liquid prepared by the aqueous extraction (steeping) of the fresh deseeded marc remaining after grapes have been pressed to produce grape juice or wine. It contains the common components of grape juice namely, anthocyanins, tartaric acid, tannins, sugars, minerals, etc, but not in the same proportions... 

In addition to anthocyanins, grape skin extract contains plant acids (mainly tartaric acid), tannins, sugars, amino acids, minerals. 

Fournand, D., Vicens, A., Sidhoum, L., Souquet, J.-M., Moutounet, M., Cheynier, V. (2006). Accumulation and extractability of grape skin tannins and anthocyanins at different advanced physiological stages. J. Agric. Food Chem., 54, 7331-7338. 

Analysis of polymeric pigments in parallel with tannin in wines or grape extracts required two 1.5 mL microfiige tubes for each sample. The first tube was made up by adding 1 mL of the acetic acid/NaCl buffer to the tube and then adding 500 pL of the diluted skin extract or wine. One mL of the mixture was transferred to a cuvette and the absorbance at 520 nm was determined (reading... 

Table 12.2 recapitulates the principal modifications of wine constitution caused by destem-nung. Despite the increase in total phenolic compounds in the presence of stems, color intensity diminishes. This long-observed fact is interpreted as the adsorption of grape skin anthocyanins on the ligneous surface of the stems. This interpretation has been confirmed in a model solution containing anthocyanins and tannins either a stem extract or the stems themselves is added, fir the first case, the tannin concentration increases considerably, while the... 

Enzymatic reactions, activated by grape enzymes, are involved in cell wall degradation. They favor the dissolution of their vacnolar contents (Section 11.7.3). Commercial enzymatic preparations have recently been developed to activate these phenomena they have pectinase, cellulase, hemi-cellulase and protease activities of diverse origins (Amrani-Joutei, 1993). These enzymes seem to favor the extraction of skin tannins over skin anthocyanins. They act on the tannins linked to the polysaccharides of the cell wall, giving the enzymatic wine a more full-bodied character than the control wine. 

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