red wine and fermentation

Posted: 3 years ago Quote #45
I recently started making my first wine. It has been in a demi john for some 4 weeks now but doesn't seem to be doing anything I expected to see bubbles in the airlock but it still looks the same as when I put it into the demi jonn. Someone gave me some of their grapes and although I said not to wash them he told me he had 'given them a good wash' would this be the cause    

Your advice would be appreciated

Posted: 3 years ago Quote #46
The whitish grey bloom on grapes is yeast which when it gets to the sugar in the juice will use it as food and turn it into alcohol and carbon di oxide making wine. If you are hoping to make wine in this straightforward way it is clearly not a good idea to wash off most of this yeast first. The first thing that yeast needs to do when it encounters a new food source is reproduce. While this happens there is always a lag time before the fermentation really gets under way. If there are insufficient yeast cells on the grapes it could take rather a long time before there’s a colony big enough to ferment your juice and in the meantime other naturally occurring organisms are going to get a look in.

I would not however recommend making wine with the wild yeasts on the skins, certainly not in this country. In winemaking regions even, winemaking yeast strains don’t tend to be found in the vineyards, but in the wineries. There a vineyard yeast may get a fermentation started but it’s the yeast that’s found its niche somewhere in the winery and developed a high tolerance to alcohol that is going to finish the job. That’s why it’s best to use a yeast that has been selected in the first place from just such an environment.

With your juice now I would suggest that you add campden tablets at a rate of one per gallon or 4.5 litres to suppress any microbiological activity that may be going on, wait 24 hours then add a good wine yeast. You have to hope that it has not come to too much harm while it has been waiting around to get started. A plea to the patron saint of winemakers, whoever that is, is probably appropriate.

I hope this helps. Anything else then let us know.