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Acid

Acid is one of those wonderful areas of winemaking that permits large amounts of mucking about. Your only contribution to the topic of acid may be to simply waft a bottle of Jif lemon at each demijohn. However, if you are prepared to expend the time and effort, whole afternoons can be frittered away in the kitchen mixing together at least four differant types of acid and performing laboratory tests to convince yourself that you are not wasting time.

If you are new to the esoteric world of winemaking you may be puzzled as to what this acid business is all about. Acid is one of the attributes of wine that conspires with many other factors to produce the all encompassing concept of quality. We are all familiar with the concept of acidity. A drop of lemon juice on the tongue will remind you. Those of you with some knowledge of chemistry will be familiar with the phrases acid and alkali. Acid equalls lemon juice, alkali means bicarbonate of soda. Mix the two together and the resultant cocktail will fizz in a satisfying manner. Wine, be it homemade or 'real' will be acidic. This is good. It adds to the flavour. A perfect wine will be acidically well balanced. An under acid (alkali) wine will taste bland, and a wine which is overly acid will taste sharp, like orange juice. The art of attaining the correct acidity is all part of the fun of winemaking.

There exists a number of scales by which we measure acidity. The one used by most winemakers is somewhat literary. The scale consists of three stages.

  • Gosh thats sharp.
  • Thats about right.
  • How uninteresting.

These statments describe the finished wine. There is no inclination to make adjustments, all that is generated is a mental note to mix things up in a differant order next time.

The winemaker who has time on his hands will broadcast this fact by taking things a stage further. The universal winemaking measure of acidity is parts per thousand sulphuric acid (ppt). Sulphuric acid never gets near wine, and is thus logically (?) chosen as the scale. Wine ranges from 3.0 ppt for a dry light wine, to 4.5ppt for a sweet full bodied wine. The afore mentioned winemaker will go to considerable pains to measure the acidity until it lies within 0.1ppt of where he wants it. The judicious adding of acid and calcium carbonate will be employed to achieve this end.

You may also remember from your school days the use of pH to measure acidity. pH counts the number of bits of acid in the wine and can be measured by indicator paper, but this does not work very well. Either you guess, or you do things properly.

You may feel justified in thinking this is all a bit unnecessary. It is. Very much so. When you start winemaking it is only nessecary to add a couple of teaspoons of acid and forget about it. Only the more adventurous go on to buy the toys required to measure and adjust acidity.

So far in this lesson I have lightly tossed about the phrase 'add acid'. How does one achieve this? The ingredients that we make homemade wine from do not, as a rule, contain enough acid to produce a well balanced bottle of wine. We must add some. 'Some' means squeeze the juice of a couple of lemons into the must. Alternativly buy a tub of citric acid and chuck some of that in. This will allow you to make fairly consistant wines.

But, (why is there always a 'but'?) the story does not end here. The winemaker can get hold of malic, lactic, citric, tartaric and succinic acids. This is before you consider the mysteries of tannic acid, but that topic alone would fill a page.

Essentially, each acid imparts differant qualities. Many winemakers use a mix of citric, malic and tartaric, but most of us just rely solely on citric. One can also obtain precipitated chalk, this is calcium carbonate, and is added to the wine to reduce the acidity.

  • Citric Acid. The is the most popular acid, it has a characteristic fruity taste. It is found in things like lemons and oranges, which is why these fruits are often included in older recipes. Citric acid also imparts brilliance to wine.
  • Malic Acid. Found in things like apples. This acid is said to help speed fermentation. There also exists stuff called malolactic bacteria. This can be persuaded to start a small fermentation in bottled wine, where the malic acid is converted to the less acidic lactic acid in a process called malolactic fermentation. This is generally considered a good thing (alledgedly).
  • Tartaric Acid. The predominate acid in grapes. Imparts a vinous (pass that dictionary!) character to the wine, but is apt to crystalise out of the wine some time after bottling because it is rather unstable in solution. This can lead to a deposit in the bottom of a bottle of previously clear wine. This in turn gives an exallent excuse to muck about decanting the wine.
  • Succinic Acid.Never used it myself, but it is said to improve bouquet and the maturing processes

As you can see the topic of acids can be as involved as you want to make it, or avoided completely. Have fun!

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