Fermenting Grape Must: Yeast Calculations

Hi. Normally, each year we crush grapes and let them self-ferment. Since we got a late start this year we missed out on the grape varieties we normally buy, so we are just going to purchase the pressed must, blend it and ferment it.

I am trying to figure out the correct amount of yeast to use for the 36 gallons of juice. Would I still use the 1.5 g/l rule? Do I need a starter?

Thanks for your help!

Hi, you are way overestimating the amount of yeast you need. Lallemand recommends 0.25 - 0.4 g per liter. For particularly difficult-to-ferment musts (from things other than grapes) I’ve gone as high as 0.5 g / l, but have never seen any need for more than that. So two or three 5 g packages of yeast will be more than enough for your needs.

Make sure you rehydrate first. You don’t need a starter; it wouldn’t hurt to have one, but there is no real need unless you only have one package of yeast and you would then have to build up the cell count before pitching.

[quote=“rebuiltcellars”]Hi, you are way overestimating the amount of yeast you need. Lallemand recommends 0.25 - 0.4 g per liter. For particularly difficult-to-ferment musts (from things other than grapes) I’ve gone as high as 0.5 g / l, but have never seen any need for more than that. So two or three 5 g packages of yeast will be more than enough for your needs.

Make sure you rehydrate first. You don’t need a starter; it wouldn’t hurt to have one, but there is no real need unless you only have one package of yeast and you would then have to build up the cell count before pitching.[/quote]

Awesome. Thanks so much!