
Wild yeasts and acetic bacteria are the two enemies of successful homemade wine making. The acetic bacteria converts alcohol into acetic acid thereby turning wine to vinegar is ever present in the air. Similarly, the yeasts and spores of fungi which turn wine insipid and flat or turn it sour are also in the air. When using fresh fruit and other ingredients from the garden or from the shops, the bacteria, yeasts and fungi are also present, but fret no more because they are easily destroyed so they do no harm.
Most ingredients used in making wine are supplied in containers and they will not be contaminated by these causes of spoilage. But, the water that you might use can contain harmful bacteria that can spoil the wine or possibly the wild yeast can cause poor ferments and these ferments could give 'off' flavors such as sour tastes.
It is not usually known that the molds on cheese, half-empty pots of meat paste and jam are often yeasts growing there for it is the yeast floating about in the air that ruins the wines that you make. So, in order to beat these souring yeasts, you must keep the fermenting wines and finished wines covered closely. Treatment of such finished wines is covered under the heading 'storing' and it is important that you cover fermenting wines.
As soon as the prepared yeasts have been added to the prepared liquid, the top of the jar should be covered with a piece of polythene and this should be pressed down all around by hand and a strong string should be tied tightly around. Through this you can keep airborne diseases away from the wine. It is also a good idea if you use a Fermentation lock instead of polythene.
The whole idea of using fermentation locks is to keep airborne diseases from contaminating the wine, so make sure the bung and lock are airtight. If not, the gas leaking will prevent air from reaching the wine and slow down the outgoing stream of gas through the leakage holes.
Having fitted the lock to the bung and jar, remember to run a little sealing wax where the bungs enter the jar and where the lock enters the bung. Actually this precaution may not be necessary, but it's better to be on the safe side. You can now remove one piece of the lock and bung and insert a new bung when fermentation ceased. The wine during this process can then be put away to clear.
Excited!