expired yeast?

[Tomas Ramirez]

hey guys quick question, i pitched two pouches of yest that were about a month past its suggested use time just wondering what your thoughts are

the yeast is imperial yeast ale flagship A07

thanks

 

[Clint Yeastwood]

Wouldn't scare me, as long as fermentation looked good. I recently ate unopened sour cream that had been lost in my fridge since way back in 2022.

 

[Clint Yeastwood]

Sourer cream.

 

[Tomas Ramirez]

Wouldn't scare me, as long as fermentation looked good. I recently ate unopened sour cream that had been lost in my fridge since way back in 2022.

hahaha right on thanks for the impute i wish i could send you a glass when its ready because that was funny

 

[MaxStout]

In the future, with liquid yeast past its use-by date, it's a good idea to make up a starter to boost cell population. In your case now, I'm assuming with ~5 gal batch and Imperial starting out at 200B cells, pitching 2 packs should be fine, as long as the yeast had been stored in a cool place.

For dry yeast, if it's kept in the fridge, it can have plenty of viable cells long after its use-by. I have pitched dry yeast 2 years beyond the use-by and had a healthy fermentation.

 

[Northern_Brewer]

https://www.homebrewtalk.com/thread...quid-yeast-after-the-best-before-date.697114/

 

[odie]

I've direct pitched liquid yeast over a year expired. It made an excellent pub ale. that same yeast has since been harvested many times over and continues to produce good beer.

 

[Bobby_M]

Can it work? Yes, if there are any cells still alive in the pack, it will ferment wort into beer. It may be slow to start leaving more opportunity for stray bacteria to compete early on. If the yeast depletes oxygen prior to reaching a decent colony size, it may struggle the entire time and stall especially on higher gravity worts. You'll get more yeast character, aka esters at low pitch rates and sometimes that good or bad depending on what you want. Probably the worst case scenario is that it fizzles out before byproducts and intermediate compounds such as Acetaldehyde and Diacetyl are cleaned up.

Imperial yeast starts with about 200B cells per pack and at 7 months, would be approximately down to 10B each. A typical 5.5 gallon batch of 1.050 wort, fermented at ale temps should have about 190B cells but in this case would have gotten 20.

Even growing it up with a starter is a little out of ideal parameters. The inoculation rate is pretty low and the growth factor is over 10 (4 is more ideal).

 

[Brooothru]

Can it work? Yes, if there are any cells still alive in the pack, it will ferment wort into beer. It may be slow to start leaving more opportunity for stray bacteria to compete early on. If the yeast depletes oxygen prior to reaching a decent colony size, it may struggle the entire time and stall especially on higher gravity worts. You'll get more yeast character, aka esters at low pitch rates and sometimes that good or bad depending on what you want. Probably the worst case scenario is that it fizzles out before byproducts and intermediate compounds such as Acetaldehyde and Diacetyl are cleaned up.

Imperial yeast starts with about 200B cells per pack and at 7 months, would be approximately down to 10B each. A typical 5.5 gallon batch of 1.050 wort, fermented at ale temps should have about 190B cells but in this case would have gotten 20.


View attachment 840080

Even growing it up with a starter is a little out of ideal parameters. The inoculation rate is pretty low and the growth factor is over 10 (4 is more ideal).

View attachment 840081

Good analysis, Bobby. But isn't it also true that multiple step-up propagations of the 10B cell count 'nearly out of date' direct pitch will approach the desired 200B cell count after a 1.020/0.5L to 1.038/2.0L 2-step propagation? It's been a while since I messed around with pitch calculators since I don't have any means of accurately counting the original colony population. But when I have an out-of-date pitch, that's the methodology I use and have never had a stalled fermentation and almost always hit my FG numbers. That said, I almost never use out-of-date pitches. When a pitch gets close to its expiration date, I preemptively do a step-up propagation to 'reset' the use-by date.

 

[Bobby_M]

Good analysis, Bobby. But isn't it also true that multiple step-up propagations of the 10B cell count 'nearly out of date' direct pitch will approach the desired 200B cell count after a 1.020/0.5L to 1.038/2.0L 2-step propagation? It's been a while since I messed around with pitch calculators since I don't have any means of accurately counting the original colony population. But when I have an out-of-date pitch, that's the methodology I use and have never had a stalled fermentation and almost always hit my FG numbers. That said, I almost never use out-of-date pitches. When a pitch gets close to its expiration date, I preemptively do a step-up propagation to 'reset' the use-by date.

Based on the OP's general awareness, at least how I see it, I didn't think bringing up multi-step starter was really going to land. I think my point was really "no, that wasn't enough yeast. It's barely enough yeast to feed into a single step starter". There are some diminishing returns once yeast requires two steps, UNLESS there's yeast that is unavailable or you have no local shop.

 

[rizziot]

When in doubt, do a starter! I have restarted yeast that's over a year old before. It might take 2-3 days, but 90% of the time you will get a starter from expired yeast!

 

[OleBrewing]

I assume most dates put on packages are in terms of known viability done by the manufacturer (this is what we are selling but after this date we can't confirm results would be adequate). I remember when liquid yeast used to come in clear plastic tubes you could clearly see difference in dead brown yeast and still viable yeast.

 

[rizziot]

I assume most dates put on packages are in terms of known viability done by the manufacturer (this is what we are selling but after this date we can't confirm results would be adequate). I remember when liquid yeast used to come in clear plastic tubes you could clearly see difference in dead brown yeast and still viable yeast.

I think I still have one of those in the back of my fridge

 

[IslandLizard]

@Tomas Ramirez, our OP.
It's almost 2 months later, how did that beer turn out?
What beer was that?

 

[hottpeper13]

Just pitched a pack of Windsor with a use by date of 5/2019. Pulled 1200 ml from the BK after 10 min, chilled and rehydrated overnite.