To follow up the introduction for how I go about yeast growing and blending, I wanted to give a worked example of how I handled blending in a more advanced scenario. It could certainly get much more complicated than this, but I think this is a good way to show my process and the potential value that yeast blending can add to brewing. As a warning, this is on the more technical/math side of things and this approach may not be what you're interested in. It's pretty dense but if you are really interested in blending yeast, and you want to do it in a controllable way, continue on. I try to break down the steps simply and repetitively so if you get it right away, excellent and sorry for the redundancy. And if you feel like you are missing something let me know. I probably wasn't clear enough and I though about this for a LONG time before actually doing the blending, so it took me a while to understand it. And it took me a while to work out the best way to do it. I think if you want to do yeast blending in a repeatable fashion you are going to want to think about blend ratios and total pitching rates. So here's how I do it in a more tricky situation...
The setup: I have been using a blend of Wyeast 3724 (Belgian Saison) and Wyeast 3711 (French Saison) for almost 2 years now and have been really happy with the results. I get a majority of the flavor profile from the 3724 combined with the reliable and excellent fermentation behavior of the 3711 and a nice complexity from additional flavor. So far this blend had been based on wanting that flavor balance with 3724 dominating, but I hadn't run any trials to find an optimal blend. So batch to batch blend ratios would swing from about 60%/40% Wyeast 3724/3711 to 90%/10% Wyeast 3724/3711 based on what I had available at the time and what splits worked best with the cell count splits I had of the individual yeasts. It was time to run some controlled yeast blend ratio trials to work out what the optimal blend is for what I want my saisons to be.
|The yeasts used in this blending
The Blending: Before I started any of the blending I got out the yeast I had and thought about the cell counts I had in each container. In the petite re-brew post I refer to 80/20and 60/40 blends, and I have also referred to these in the bottles I gave away. In my brewing notebook I refer to 85/15 and 70/30 blends, which were my actual target going into this. The 80/20 and 60/40 must have come out of what I thought I had done after the fact (as it turns out that was not the case).
Anyway, I made a table with my target blend ratios and the total number of cells I would need in each carboy based on the Mr. Malty calculator. I had jars of ~110 billion and ~150 billion cells of Wyeast 3724 and of ~65 billion cells of Wyeast 3711. Conveniently for the main two carboys the total desired pitch worked out to 100 billion cells each based on my OG and volume. I also knew full and empty weights of my jars (I approximated the empty with another jar of the same style/size). I blended the 150 billion cells of 3724 and the 65 billion cells of 3711, making a blend of roughly 70/30 with ~215 billion total cells.
|My Target Blends
Knowing the full weight of this jar and an approximated empty weight, I knew the weight of my blend slurry which was ~215 billion total cells (150 of 3724 and 60 of 3711). For a pitch of ~100 billion cells of my 70/30 blend I needed to add a bit under half of this slurry. After adding the appropriate pitch of this slurry I would have about 115 billion cells left in the 70/30 blend (210 to start - 100 needed, approximately 80 billion cells of 3724 and 35 billion of 3711 left).
To this I added the extra 110 billion cells of 3724 from the other jar, making an approximate total cell count of 225 billion cells composed of ~190 billion of 3724 and ~35 billion of 3711, a blend ratio of roughly 85/15. Knowing the new full mass of this blend and the same approximated empty jar mass I could add a bit less than half of what I had to add ~100 billion cells to the target 85/15 blend, leaving me with ~125 billion cells in 85/15 target blend left over.
Okay, so I've added the yeast to my first two carboys and it all worked out pretty smoothly. Now I have 2 carboys remaining: 85/15 blend plus brett and lact and the carboy with Yeast Bay Wallonian Farmhouse (which I'll call WF from here on out). For the WF blend I have a blend ratio of 62% 3724, 27% Wallonian Farmhouse and 11% 3711 in my notebook. I honestly don't remember my reasoning for such a precise and strange ratio. I had no reason to choose a specific amount of Yeast Bay yeast to add, except that I was happy with the character from using it in my Barrel Aged Saison. So the choice probably came from how many cells I needed and how much 3724 and 3711 I had left over. If I actually worked it out that exactly I must have been pretty sharp at that point in the process.
I had ~125 billion cells left and based on volumes and OG I would need ~85 billion cells total in the +brett and lacto (+BL) treatment and ~55 billion cells total in the WF treatment. I couldn't meet my desired pitch counts with the 3724 and 3711 I had left, but that's good because I would be adding other yeast/bacteria. I would slightly underpitch Saccharomyces to the +BL carboy and make up for this with brett and lacto to come to my target, while potentially overpitching total cells a bit. And I would underpitch 3724/3711 and add Wallonian Farmhouse to hit my target of 55 billion cells in the WF treatment. Back calculating based on those targets I wanted to add approximately 75% (~82 billion cells) of 125 billion remaining 85/15 blend to the +BL treatment, leaving ~43 billion cells of 3724 and 3711 for the WF treatment. Since that is a pretty even split, it must have determined the strangely specific 3724/3711/Wallonian Farmhouse ratio from above for the WF treatment.
I find it easier to think about the blending from this perspective after the fact and I would suggest carrying on like this, but during my actual blending I did the last 3 blends in the the opposite order (adding ~125 billion cells of the target 85/15 blend to a combination of WF and +BL treatments and leaving the rest for the normal 85/15 target blend).
I kept the Wallonian Farmhouse yeast separate, since it was only going into one carboy, to make up the difference in case I messed up on one of my pours. The same can be said for the brett and lacto. I didn't add known numbers of cells of those, but I could add more or less based on how much Saccharomyces I added. So with this target plan all thought through, I went ahead and did the blending. My actual blend ratios are shown in the table below. As it turns out, my Saccharomyces blends were 86/14 (Wyeast 3724/Wyeast 3711), 70/30 (Wyeast 3724/Wyeast 3711), and 69/12/19 (Wyeast 3724/ Wyeast 3711/Wallonian Farmhouse). So a pretty good job hitting my targets overall.
|My actual blends. Wallonian abbreviated Wall. Cells added from (slurry mass added) / (total slurry mass). Cells of each type added from (total cells) * (% of each type) /100. Total cells remaining determined from (initial counts) - (added).
Hopefully this approach made sense. Definitely ask if you're stuck on something. And hope it proves helpful to you if you decide to try your own yeast blending. It definitely doesn't have to be as complicated as this so don't feel scared away from doing your own blending if this seemed too much. It's something I had to work up to from doing a bit of more simple blending first but I think it is a valuable approach to optimize your blending and to controllably try out different yeasts.