This study indicates the repeatability of various structure indices of phenolic compounds (GLORIES Indices). It is excellent for the gelatine index, the HCl index and tanning ability, good for the ethanol index, total tannins and the DMACH index, but less satisfactory for the dialysis index. A relationship which is not directly proportional can be observed between the gelatine index and tanning ability, but also a certain relation between tanning ability on one hand and total tannins-TAI on the other. There is a good correlation between gustatory astringency, the gelatine index and tanning ability, and the latter measurement, being the most rapid (only 45 mn), turns out to be interesting for sorting wines before fine tasting sessions.
Different techniques of pre-fermentation (cold or hot maceration, bleeding), fermentation (submerged cap) or postfermentation (final hot maceration, maturing on the lees) are tested. The results are very variable according to the wines and their age. Favourable results with young wines are not always confirmed after a few months’ maturing. The choice of each technique should be made according to the characteristics of the grapes and the probable consumption dates.
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