In the normal way, wines clarify to brilliance without assistance of any sort, except periodic racking. This is because the method used, rather than the recipe or the type of ingredients, was the sort that does not allow for pectin or starch to appear in the must. These substances are the two most troublesome and most common causes of non-clarification.
As we have just seen, the larger particles of fruit pulp and the heavier yeast particles settle out in the early stages to form the initial heavy deposit. Even the lighter solids will settle out when the upsurge of carbon dioxide gas produced during fermentation ceases. Later, the almost weightless solids settle out. They are too light to settle out by themselves, but eventually they join up to form heavier particles and fall to the bottom of the jar. Thus wines made by methods that do not allow the presence of pectin or starch in the must will not present a clarifying problem.
When starch or pectin are present, they form a barrier which prevents the almost weightless solids from joining up to become heavier. In this way they prevent the solids from settling out. The problem is increased by the fact that the clarifiers used to clear wines not affected by starch or pectin will have no effect on these two substances except, in certain cases, to worsen matters.
The presence of pectin in a wine is almost certainly due to a faulty method of production. Pectin is found in all fruits in varying quantities. Heating the fruit releases acid which, in turn, releases the pectin. This is why the sulphiting process for fruit is so popular: it does not involve such problems. Wines produced by this method have the flavour of the raw fruit, which is most popular. But those who like wines with a stewed fruit flavour will use the pectin-destroying enzyme included in the methods to ensure a brilliantly clear wine.
Thus the sulphiting method and the boiling method will make distinctly different types of wines from the same ingredients.
Roots, of course, are a different matter. Potatoes, parsnips and carrots must be boiled in order to destroy soil bacteria. If we did nothing about this it would cloud the wine heavily in the same way as pectin, but we use a starch-destroying enzyme as included in the methods to ensure a brilliant wine. This enzyme is known as fungal amylase. If, however, you already happen to have some wine in store that is cloudy a simple test can be carried out to find whether pectin or starch is causing the trouble.
Take about 3 tbs (1 fl oz) of the wine and add three to four times the amount of methylated spirits. Shake well. If much pectin is present, jelly-like clots or strings will form almost immediately. If little pectin is present, some jellying will occur after about an hour. So keep the sample for a while if immediate clotting does not take place. If pectin is causing the trouble, a pectin-destroying enzyme must be employed; nothing else will do. When the pectin has been destroyed, the solids causing the clouding will join up and settle out.
Any of the pectin-destroying enzymes such as Pektolase — often call ‘pectin enzymes’ — are excellent and should be used according to the directions of the supplier.
As I mentioned before, starving the yeast of sugar in the early stages will often induce an enzyme in the yeast to convert starch to sugar. But this does not always happen so that starch causes the same kind of trouble as pectin. Root wines and those made with grains or apples are the offenders here.
To test for the presence of starch, take 2 or 3 tbs (about 1 fl oz) of the wine and add a few drops of tincture of iodine. The sample will turn dark blue or near black if starch is causing cloudiness in the wine. To test this reaction before using wine, you can see the effect if you drop a tiny amount of iodine on a slice of potato. If starch is causing the cloudiness use a starch-destroying enzyme as directed by the supplier. This takes care of the major problems which, as we have seen, should not arise if reliable methods are used. But what of hazes caused by neither pectin or starch? There are many proprietary clarifiers which will take care of these, and it would not be fair for me to recommend one against the other. All are reliable and all are supplied with directions for use.
However, if you want to try something quite handy, then egg-white should prove satisfactory. Up to 40 ltr (8 gall) can be cleared with one egg-white. When using this it is best to put the wine in an open vessel, such as a fermentation vessel. Whisk the white of an egg to a stiff froth and mix it thoroughly with the wine. Return the wine to its jar. After clarification has taken place, rack in the normal way.