Yeast Starters for Yeast Blends
TroubleShooting
Simon Ryr - Woluwé-Saint-Pierre, Belgium asks,
I’ve got a vial of White labs WLP670 (Farmhouse Blend), which contains a saison strain and a Brettanomyces strain and the “best before” date is slightly expired (less than a month). I guess I’d better make a starter to wake up my culture, but as the two strains have pretty different reproduction speeds and metabolisms, wouldn’t a “classic” starter change the balance between the strains?
If I had to choose between using an old mixed yeast culture that has the “correct” ratio of yeast cells that the yeast supplier used in the blend or using a vital culture with a different ratio of cells made from that old culture, I would always choose the vital culture. The thing about this question is that the first option is probably not quite what it appears to be because not all yeast strains lose viability and vitality to the same degree during storage. But like you state, these yeasts have different growth and fermentation rates and these differences are true during propagation and fermentation.
In mixed culture fermentations, especially when the organisms are not merely different yeast strains, there tends to be several phases of the fermentation where the various populations rise and fall in waves. In the case of a mixed Saccharomyces and Brettanomyces fermentation, the Saccharomyces fermentation rate will be faster than the Brettanomyces fermentation. The first wave of activity will result in the base beer and the second wave will see the development of the phenolic aromatics associated with Brettanomyces and further reduction in apparent extract as limit dextrins are consumed.
I really would not worry too much about changing the balance of the strains. By making a starter you will insure that you have a healthy cell population and you should expect to see a rapid first fermentation followed by a slow secondary that brings with it funkiness and dryness.
