Ask Wine Wizard

Wild Fermentations

TroubleShooting

Jack Kerr — Santa Fe, New Mexico asks,
Q

I tried to let a natural fermentation work on a 3-gallon (11-L) sample wine. At five days no discernible action was taking place and I added a cultured yeast. Should I have waited longer? When should a natural fermentation be expected to commence? What are the indicators?

A
Well, I would’ve inoculated right off the bat if I didn’t see anything happening within 24 to 48 hours. Contrary to popular belief, yeast cells that can carry out a complete alcoholic fermentation rarely come in on the fruit from the vineyard. The species that do are typically those kinds that can only ferment to about 5% alcohol. Especially if you are using frozen juice, must, or concentrate, don’t expect to be able to rely on any indigenous microbes from the raw material to get your fermentation going. The freezing or concentration process will have significantly knocked down the percentage of viable native yeast cells. The microbes that conduct so called “natural” or “feral” complete alcoholic fermentations usually come from the wineries themselves. This is why “well-seasoned” wineries, meaning those that have had a history of many successful fermentations over many harvests, are more able to have complete fermentations without having to inoculate. These yeast strains, ambient in the air and on equipment, are robust and have been selected over time as strains able to conduct a fermentation to dryness
Response by Alison Crowe.