Step 8: Add yeast
Any wine or beer grade yeast is good for this. You can add it straight into the juice, but if you have used sulphur dixide to sterilise your juice, you should allow 24 hours before adding the yeast. The wine yeast you add will quickly crowd out any traces of other natural yeasts. It will use up the oxygen in the juice to breed, and will start turning the natural sugars into alcohol.