So I'm planning on brewing a 10 gallon batch of a chocolate oatmeal stout next Saturday or Sunday. However, i was only able to obtain one vial of WLP013 for the beer. The yeast was manufactured on April 16, 2016. According to Beersmith, the yeast viability is 50%. It also recommends to make a starter of 2600 mL with 2 vials to achieve the cell count needed. Mrmalty.com says my yeast'a viability is 10%, Brewcipher says it's 26%, and Brewersfriend says it's 0%....I know it isn't ideal to only have 1 vial but I'd like to make it work with what I have. I was planning on making a 2,000 mL starter of 1.03 gravity to get it started. I then wanted to make an additional 2,000 mL but of 1.04 this time. According to Brewersfriend, I would achieve a proper pitching rate for the beer. What do you guys think? Would a third step be necessary? I have a 5,000 mL and a 2,000 mL flask that I can use. I will mention that the intended OG will be 1.068. I planned on making the starter tomorrow.
Brewersfriend says viability is 0% and also says that a two-step starter (starting with 0 yeast) will net you an appropriate pitch rate? Fascinating. Assuming you don't have the means to count cells, my recommendation would be to use whatever calculator you trust the most, i.e. the one that has given you good finished results in the past. Too bad your WLP013 didn't come in one of the new squeeze tubes. Then you could assume full strength after 6 months. </sarcasm>
Did you miss this part?... If anyone gives you advice that seems more definite than what I said there, I'd say they are blowing smoke. Nobody knows how much viable yeast is in your vial.
I tend to speculate that the die-off rate is projected to be linear over time, but actual results may not be linear. And that the yeast strain may have an impact, yet not all are tested. Perhaps only one. And that the storage quality may have an impact (medium as well as temperature stability over time). I would like to hope that the die off rates are based on a previous study. Perhaps the rates vary because there were multiple studies done. And who would have sponsored such a study? I would think it was the yeast lab themselves. Because of all of this uncertainty, I would use the 10% figure. I assume the 0% is an arithmetic error and I would toss out the 26% because it isn't in your best interest to under pitch. But there is only one way to know with any precision - http://www.whitelabs.com/beer/cell-counting-viability-testing-0 Actually, if it were me - I would consider a step starter and delay the brewday accordingly.
Thanks. My plan was to make the initial 1.03 starter and let it ride for 2 days, then make the second at 1.04 and possibly a third. You don't thing that's enough time for next Sunday?
What @VikeMan was saying is that no one can give you advice on how much yeast is in there. The reason you're getting multiple calculations from different sources is that yeast that old are going to be rather limited...the exact amount unknown. If you're going to try an use that yeast vial (I wouldn't, especially not for 10 gallons) you need to assume very low numbers, and your first step of the starter should be in the range of ~1.020: In general, starter wort should be between 1.030 and 1.040 (7 - 10°P). If you're trying to revive a stressed yeast, like culturing up yeast from a bottle conditioned beer or from an old slant, use a lower gravity starter wort around 1.020 (5°P). Lower gravity starters are easier on the yeast, but result in less growth. High gravity starters result in more growth, but are more stressful for the yeast. Exceeding the higher end of the range is stressful on the yeast and should be avoided. Logsdon says, "Generally, you'd use the lower end of that range [1.020 SG, 5°P] for coming off a plate or slant or very old yeast. Yeast don't get used to a high gravity environment, and the high osmotic pressure can really stress the yeast. Don't forget, you want to increase healthy cells in a starter more than you want to increase the number of unhealthy cells." http://www.mrmalty.com/starter_faq.php Anyway, good luck...but my honest opinion would be to get different yeast, or find more vials.
I'll bet the 50% viability is about right, assuming good storage conditions. I'd recommend a two step starter, first just 1 liter then step up to a gallon. Or just do a single step one gallon and hope for the best -- I think it would most likely work.
Make a one gallon batch of your stout, hoy that lot in on your full brewday Actually if it's that old, do something like 350ml then 3.5l or similar
Even a fresh 100% viable vial into a one gallon starter wouldn't yield enough yeast for this batch (going by most peoples' typical desired pitch rates). And that's a best case that we know is not the case. The basic problem, as @JohnSnowNW pointed out is that you're trying to stretch an unknown, but likely pretty low, cell count for a 10 gallon batch of 1.068 wort. Again, I'd say go with the calculator that has given you the best results in the past. Or if that's worrisome, start with a modest, low gravity starter, and then when it's done, eyeball the yeast cake volume and make an educated guess about how many cells there are. Then use your favorite calculator from there. But honestly, unless this is a hard to get strain, I'd start with fresh yeast, possibly two vials, and build an appropriate starter from there.
So after making a starter of 1L at 1.02, I saw some little fermentation occurring. On the second day, I threw in a 1L at 1.04 and that had a nice little krausen after a day. Yesterday, I pitched roughly a 3L at 1.04 and it has some great activity going. My LHBS was able to get me an extra vial of the WLP013 today for me to pick up. Would it be *necessary* to pitch in this vial as well? According to Brewers friend, I'll have roughly 800 billion cells and only 500 or less is needed for 1.068 OG 10 gallon batch. Would I be risking over-pitching if I throw in this extra vial?
At this point, I'd recommend letting the yeast in your starter settle out and then estimate the volume (in mililiters) of the yeastcake. Then use BrewCipher or Mr. Malty (there may be others) to find out if that volume likely has enough cells (whatever your target is). BrewCipher has some slurry parameters you can play around with. I think Mr. malty does too. Or just trust that you probably have enough, given your assumptions and starter step sizes. I wouldn't throw in the extra vial, unless you have good reason to believe your count is low. Overpitching is generally more benign than underpitching, but I wouldn't do it if I was pretty sure it would cause an overpitch.
Thanks, the plan was to let this final starter go until 5 or so and then put in the fridge to crash it. Then asses the thickness of the slurry tomorrow and decant. Will 12-18 hours be enough time for the yeast to flocculate?
If you said you were using WLP002, I would have said definitely enough time. Not sure about WLP013...I don't have a lot of experience with it. But it's a pretty popular strain, so I'm sure someone will know.
