I give you credit for being so dogged in your desire to try fermenting! The great news about yeast is that, as I’ve often said in these columns, yeast live everywhere around us. They are naturally present on the skins of many fruits and vegetables and even in the air you’re breathing right now. The trick is to trap and encourage the right kinds of yeast that will do the kind of work you want them to do.
Bread yeast will indeed turn sugar into alcohol but only to a point. They are bred (no pun intended) to ferment only to low (think well under 10%) alcohol levels and will naturally peter out due to alcohol toxicity at higher levels. Because of this, bread yeast aren’t very well suited to fruit winemaking, where an alcohol level of at least 11% is desired.
I checked out some of the online “grow your own yeast” tutorials and some of them seem to have the right idea — to the extent that it will work. Most tutorials seem to me to be like trying to create a kind of sourdough starter. Because I’ve never tried making my own yeast culture per se, I’m not sure I want to give a step-by-step here. However, what I have actually done in the cellar is something that many winemakers do the world over: Ferment wine with naturally occurring, or “feral” yeast. As I suggested in an earlier question, more information that will help you with this is detailed in the story beginning on page 52 of this issue.
You may have heard this term called “native” or “natural” fermentation. I bristle at the latter term because all fermentations are natural whether they are conducted by an introduced yeast strain or by a strain (or strains) that just happened to wander by.
Here’s how I set myself up to optimize results with a feral fermentation:
• Start with clean, ripe grapes around 23-24 °Brix. Because you’re going to be relying on ambient yeast you don’t want any other microbes competing with them so make sure they are free of rot or molds.
• Destem them (or at least leave only about 20% grapes with stems)
• Put the grapes into a clean container, preferably one in a place where the temperature will remain around 55 to 75 °F (13 to 24 °C). In my winery, I use a temperature-controlled stainless steel tank, but a food-grade bucket in a climate-controlled room can work too, because the volume (and heat produced by fermentation) will be so low in the case of the latter.
• Add around 20 ppm sulfur dioxide. If the country you live in doesn’t sell winemaking supplies this may be hard to find. But since potassium metabisulfite powder has uses other than winemaking (like preserving dried fruits) you may be able to buy some. This is an important step because the sulfur dioxide will repress the bacteria and yeast that you don’t want; wine yeast tend to do fine with sulfur dioxide levels this low and are therefore naturally selected.
• Cover loosely with a tarp or lid. Mix up or “punch down” the floating cap down into the juice about three times a day. With a little bit of luck, within a day or two, you should begin to smell
I recommend starting small — perhaps with a bucket of grapes — and try to see what kind of wild yeast you can capture and grow. If you are successful, and ferment a must to dryness (when all sugar is gone) you know that you’ve got the right stuff and can branch into bigger batches. Good luck!
• Make wine anytime from grapes with must that has been frozen immediately after crushing. Here’s how: http://winemakermag.com/story1225
• Understanding wine yeast chemistry will help you make better wine. Here is what the home winemaker should know about the inner workings of yeasts and how it affects the wine: http://winemakermag.com/story1078