Premature fermentation of wine must. What to do?

Question

I recently took delivery of a five gallon pail of white wine juice. Supposedly, the juice had been refrigerated on its trip from California and stored in a cool warehouse here in my home town. However, when it was delivered it was actively fermenting. I don't know what the original gravity was, but the current gravity is around 1.045.

What should I do at this point? I have a packet of Lalvin K1V1116 that I was planning on rehydrating and pitching. Should I pitch this yeast, or is it now too late for to have much effect?

Should I add sulphite to try to knock down the wild yeasts? Or will this just interfere with the yeast I'm pitching?

Should I oxygenate or will that just oxidise the must?

Can this wine be saved, or am I out of luck?

Answer 1

First thing is to store it in a cool place to slow down the fermentation while you make your plan of attack.

If there is a specific yeast profile you are looking for, then it's probably best to knock out the existing yeast now - depending upon the OG, current SG of 1.045 could well be less than half way through the fermentation, so you still have plenty to go. You can add sulphites to knock out the yeast (such as 1 campden tablet per gallon), although you'll need to leave the must for at least 24 hours, loosely covered (no airlock) so that the sulphur dioxide can dissipate. (It's not like Potassium Sorbate, which is a permanent yeast inhibitor.) K1V1116 is tolerant to high levels of sulphur dioxide, so 24 hours should be plenty. Rehydrate the yeast first, as Lalvin describes, to get the maximum cell count and then pitch. Since the must is already partly fermented, your pitching cell count should be high enough, and aerating the must isn't necessary.

Take another hydrometer sample, and taste/smell to get an idea of the flavor profile of the wild yeasts. If they are not contributing any unpleasant flavors now, then the wine should be fine.