Sugar turns to alcohol...

Heres a photo of a hydrometer measuring the juice Brix levels. Brix is the measure of the soluble solids in the juice, effectively translating into the amount of sugar which in turn can tell us the amount of potential alcohol we will end up with once fully fermented. The basic equation is that yeasts consume the sugar and the result is ethanol and CO2 gas. Unfermented grape juice often has around 250g/L sugar which is sweet !, twice as sweet as Coke and sweeter than almost all other fruits by a long way. In this picture here our 2009 Pinot Gris juice prior to ferment is around 23 brix which may equate to around 13% percent alcohol give or take 0.5% juice to factors such as temperature. Once the juice is fermenting we need to monitor the drop in brix regularly as well as making sure the yeasts are well fed (otherwise they can start to produce off flavours) and keeping an eye on juice temperature and residual sugar levels too.