. . . plays a vital part in determining wine quality. Lack of acid will mean a poor fermentation, and a "medicinal" taste in the finished wine, which will also lack character and seem insipid. In any wine it is essential that acidity, tannin content and degree of sweetness should be "in balance" according to the type of wine being made (a sweet wine will need more acid than a dry). A quarter of the original acidity of a must disappears during fermentation (so that tasting one's must affords some guide) and a finished wine should have between 5 parts per thousand (dry) and 7 parts per thousand (sweet). This, in most recipes, will be obtained by adding the juice of one, or two, lemons, or H—^ oz. citric acid.

A simple way of testing the acid content of a wine or must is to use B.D.H. Narrow Range pH indicator paper (aim at a colour reaction equivalent to between pH 3 and 4). This is not entirely accurate but it is probably enough for most of us.

Those wanting more precision should note that the desirable acidity of table wines, in terms of sulphuric acid, is from 4 to 6 grams per litre, according to type.

The only really satisfactory method of assessing acidity is by titration, and kits for this purpose can be bought for as little as £l. A graduated pipette is used to take in a given quantity of the wine to be tested and this is run into a beaker. A piece of blue Litmus paper is added and this is immediately turned red by the acid present. A commercially-prepared potassium hydroxide solution (11.43 grams of pure potassium hydroxide per litre, the equivalent of 10 grams per litre of sulphuric acid) is then carefully added, until the Litmus paper turns blue again. Note how much solution you have used and from the chart provided you can tell the acidity of the wine. Do three such tests. and take the average.

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