I’ve ordered liquid yeasts a few times and it really pisses me off when it arrives and its 3 months old according to the manufacturing date! Anybody else run into that? I just ordered WY1272 and if it comes more than a month and a half old I’m calling the store and complaining, they charge enough for it that they ought to keep better track of it… first in - first out method isn’t all that difficult and yeast viability is a huge issue when making starters! >:(
IME, viability isn’t as big a deal if you’re making starters. I’ve successfully used 3 1/2 year old smackpacks, although it’s nothing I recommend! Fresher is always better, but 3 months old isn’t a terrible problem. Although, if you’re ordering from a place that has a decent turnover, it is a bit baffling why they have packs that are 3 months old.
Three months is still ~40% viability, kind of a drag but not hard to deal with. It’s a bigger deal as a customer service issue than a brewing issue.
I always make a starter with smack packs. That said I found a smack pack under the vegetable drawer in the fridge a couple years ago that was 6 years past its mfg. date. I thought I would smack it and see if there was any activity, and after a week it had inflated itself. I made a starter and brewed the beer I usually make with this yeast, and it was virtually identical.
I routinely make starters from smack packs that have been in the fridge for 6 months or more as I buy all the ingredients and the best laid plans go astray…
In ten years I have only had one bad experience with a wyeast pack that inflated fast and popped, breaking the seal at the top of the foil bag. It produced an obviously infected beer with multiple weird flavor characteristics.
I’ve never had that problem, but if I did I’d contact the seller and ask for a replacement and/or a refund. 
My local shop sells yeast over 6 months old at 1/2 price. If I plan my beer far enough in advance I usually buy these. I’ve seen it take up to a week for the smack pack to inflate and then a couple more days for a starter. I never had a problem using one of these 6 month to 1 year old packs.
Maybe I’m misunderstanding the calculator on MrMalty? According to yeast viability determines the number of smackpacks or vials needed for the required size for the starter?
You can also reset the calculator to use a single pack and it will tell you how big a starter to make.
Rule of thumb.
If you make 2000ml starter at 1040 and pitched one vial into it, you will get about 2 vials of yeast.
If you need 4 vials (lagers) make 4000 ml starter and pitch one vial into it.
This goes for average beer (1050 or so) and 5 gal of wort.
If you have higher gravity beer or more wort you need more yeast.
Do you mean using the slider bar at the bottom to increase the “Growth Factor”?
This is a good question. Both that slider bar on Mr. Malty and the table in Palmer’s book indicate that the final yeast cell count in a starter is dependent on the amount of cells you start with. For example, using the table on page 69 of How to Brew if I pitched 50 billion cells into a 1.040 4 qt starter I’d end up with 206B cells. But if I pitched 100B cells into the same 4 qt starter I’d have 305B cells.
My initial question before I thought this through was: Why is that? Wouldn’t the yeast just keep growing to the same level no matter what the pitch cell count?
However on further reflection I get it. The yeast are going to keep eating and reproducing until the food is gone. A higher initial pitch rate means more cells reproducing and therefore a higher ending cell count using the available food.
My order from Midwest arrived yesterday, this is the freshest yeast (WY1272) I’ve bought yet, mf’d on 12/01/09!! ;D Maybe in the past its been the strain of yeast I’ve ordered? I’ve gotten old yeast from both NB and Midwest so thats about the only thing I can think that may be the reason?
I’m a bit tossed on what I want to make now, an ale or a stout. :D One or the other is about to be born, I may make both and use some S05. ;D
I don’t even bother letting them inflate. I smack it to get the nutrients from the pouch and just pitch. The starter is the proof.
Really interested to know if anyone has more info or experience of using old liquid yeast packs or old stored yeast slurry?
Out of intrigue I’m having a go at propagating from a 100 Billion (estimated!?) overbuild yeast slurry that has been sitting in the fridge since February 2019!? :o
For the experiment I’ve gone with an assumed 25 million remaining cell count for the 36 month old slurry using Homebrew Dad’s model “running” total - you lose 20% in one month, 20% of the remaining balance the next month, and so on.
Step 1 - 100 Fold - 0.016 litres of 1.040 wort with 1% yeast nutrient - 2 million/ml Inoculation Rate - 2-3 Days on stirplate = 2.5 Billion Cells
Step 2 - 10 Fold - 0.16 litres of 1.040 wort with 1% yeast nutrient - 15 million/ml Inoculation Rate - 2 Days on stirplate = 25 Billion Cells
Step 2 - 10 Fold - 1.6 litres of 1.040 wort with 1% yeast nutrient - 27 million/ml Inoculation Rate - 2 Days on stirplate = 250 Billion Cells
All steps calculated using yeastcalculator.com with K. Troester stirplate method.
Definitely something happening already with Step 1 after 20 hours!?
What are folks thoughts? Cheers! Dan.
I have revived a 3 1/2 year old smack pack of WY3787. Started with about 100 ml of 1.020 wort and stepped it up a few times. No stir plate. No thought of cell count. Ended up making a very nice tripel with it.
I keep a few cultures in my fridge that I feed fresh wort once or twice a year. No problem with viability making starters from them.
The longest I’ve gone with slurry has been about a year and a half before growing it back up, but I’ve been successful with growing up a pitch from bottle dregs that were aging in my basement for a few years.
The key with older, low-viability cultures is just to go slow and be meticulous with your sanitation. When I wake up an old slurry I keep the beer it was stored under and mix with an equal amount of normal strength starter wort. This gives a half strength starter to take it easy on the old yeast. It also starts off with some hops, alcohol, and reduced pH from the beer as protection from infection while the yeast wakes up.
Nice one Denny ;) Good to know it’s possible. I can’t seem to find much info at all on yeast counts of old yeast. I haven’t got a microscope… but it would be great to have some ball park figures of what’s actually still viable in old packs to start propagating with, just guessing at the mo. It’s WYI469 on the stir plate, colours changing nicely, will go to step 2 today. Also have a WY1187 Feb 19 smack pack which I’m waiting to swell up. Had one take a whole week previously. I have 8x Feb 2019 Wyeast packs that I’m very reluctant to bin. One of which is WY3787. What was the Tripel you made? 
Cheers! Dan.
Nice one Eric ;) I think I’ve kinda done the same thing? Because I was starting with just a tiny 16ml of 1.040 wort, I kept a little of the beer that the yeast was stored under, just enough for the stir plate bar to spin effectively in a 1L flask. Am wondering if this will effect my yeastcalculator.com figures? As like you say the 16ml 1.040 wort will have now been diluted. I’m hoping this won’t make too much difference as the beer has been fermented out and will maybe act as a familiar environment and protector medium for the yeasties to fool around and procreate in? My Step 1: 100 fold - 2 million/ml Inoculation Rate may be a problem, although I have read that a 50-100 fold first step is often used in breweries. Cheers! Dan.
Interesting! ;) How long have you had them? Do you just add fresh wort on top or do you decant then add fresh wort? What numbers do you go with for viability? Have you every counted under a microscope? Cheers! Dan.
I don’t worry about cell counts. My concern is yeast vitality. No need for the pack to swell. Just make your starter.