Yeast Expiration Date Approaching

[jpr.edison]

Hi. In the next three weeks I have two packs of liquid yeast that will reach their "Use By" Date. I've had them since March and they have been stored in the vegetable crisper of my fridge. The earliest I can see myself using them would be mid-fall. Questions:
Is there anything I can do now to increase the shelf life?
Am I better off tossing them and purchasing new packs?

I always use a starter solution when I use liquid yeast.

Thanks
Jim

 

[VikeMan]

First, the "use by" dates are almost meaningless, as they are based on some "one size fits all" dumbed down assumptions. Not that you or anyone else is dumb, but the yeast manufacturers treat us as if we are.

Every day, there are less live cells than the day before. That's true both before and after the "use by" date.

The best thing to do is use a yeast calculator to figure out how much yeast you need, estimate how much you have, and compute what size starter (if any) is needed to bridge the gap.

 

[jpr.edison]

Thank you VikeMan

 

[odie]

I've used dry yeast close to 2 years expired and made great beer...then harvest that yeast and kept going with it...

Probably the same with liquid yeast too...store in fridge and forget the dates...

 

[MaxStout]

So many variables: conditions during storage at the store, conditions during shipment, conditions while stored by you, etc. The "use by" date is not a bright line.

Make a good starter.

 

[Golddiggie]

As mentioned, use a calculation tool and build starters for the batch you'll be using the yeast with. Go for either two or three starter steps. Chill/cold crash the starter between, decant spent starter wort and add fresh. Use a stirplate helps you make smaller starters that are also finished sooner.

If you're really concerned, make a starter sooner and store in a sanitized jar. Record what the tool says your end cell count will be (viable cells) and use that to base the starters you'll make closer to brew day.

 

[VikeMan]

Go for either two or three starter steps.

I would say go for two or three steps if needed. It's often not, and we know nothing about @jpr.edison's batch size or style, or his actual brew date. Which is where a calculator comes in.

 

[IslandLizard]

The best thing to do is use a yeast calculator to figure out how much yeast you need, estimate how much you have, and compute what size starter (if any) is needed to bridge the gap.

Exactly, and making starters is the only way to arrive at a well estimated, proper pitch rate.

Here's the tool/calc I use most often:
BrewUnited's Yeast Calculator
Note, certain cells are not editable while a few will adjust automatically depending on other cells' content, but can be reset to values you want. Keep an eye on that. It becomes 2nd nature after a few times.

Also, the yeast in WhiteLabs' Pure Pitch packs have a much better viability record than any other, due to the unique packaging method. The "use by date" is 6 months after manufacturing date. I'd estimate your yeast's viability to be 50-25%, depending on her history and storage temps.

But... 1-3 days in hot transit may kill more cells than 3 years of cold storage in the fridge.

 

[IslandLizard]

BTW, I'd start making those starters early, like 2 weeks before brewing, just in case you need to step up. Or make them ASAP, and store the slurries in the fridge. The viability count down starts ticking from then on, again.

I just revived a bunch of stored slurries, saved out from previous starters, that were made over 4 years ago (time flies...). It took a week to propagate, but they look great!

There was less than one drop worth of thick, gooey yeast slurry stuck to the bottom of one of the small 8 oz jelly jars. I added 4 oz of leftover starter wort to it. I left it on the counter. 5 days later it had fermented out, and precipitated 1/16" of slurry on the bottom! That's about 10-20 billion new cells already!

 

[Golddiggie]

I would say go for two or three steps if needed. It's often not, and we know nothing about @jpr.edison's batch size or style, or his actual brew date. Which is where a calculator comes in.

Often I was doing two starter steps so that I could use either my 2L or 3L flask. I used the Proper Starter canned wort to make them, so I would make them in 1L increments. There were a couple of times, in the past year or so, where I only needed a single starter step. The additional steps were typically when I bought yeast too far ahead and the reduced vitality made it a good idea to do the multiple steps. I would also do multiple steps when using yeast from my frozen bank.

 

[ScrewyBrewer]

If you figure on a 10% yeast cell count loss per month, only 40% of the yeast will be viable after six months. For me, it is easier just to cut my losses and buy fresh yeast. I say this because the cost for DME and the time it takes to step up the cell count is not worth it.

 

[Beermeister32]

I believe beer yeasts were a couple billion years old by the time the ancient Sumerians began making beer. They weren’t concerned about expiration date. Neither were the Neolithic hordes brewing 11,000 years ago brewing their half-baked bread loaves.

Then there are the 200 year-old bottles of beer with yeasts resurrected from the bottom of the ocean.

I say plow forward. Here is an interesting video from Carlsberg when they were re-creating 19th century beer using original yeast they had discovered:

 

[shoengine]

Anecdotally, I can say I used an Imperial pack that was six months past its pull date, and it about blew the top off my 5l flask in about a day.

 

[Chuckbergman]

I had a homebrew buddy give me a brick of SO4. I kept it sealed in the fridge but brewed with it for years. I have to admit near the end I had to use more grams to get fermentation going - but hey I had free yeast for like 4-5 years!

 

[RM-MN]

If you figure on a 10% yeast cell count loss per month, only 40% of the yeast will be viable after six months. For me, it is easier just to cut my losses and buy fresh yeast. I say this because the cost for DME and the time it takes to step up the cell count is not worth it.

Their are people who claim 10% yeast loss per month and people who claim it is only 1% per month (properly refrigerated). Guess which group of people sell yeast.

 

[Steveruch]

I've used dry yeast close to 2 years expired and made great beer...then harvest that yeast and kept going with it...

Probably the same with liquid yeast too...store in fridge and forget the dates...

My last batch of bitter was fermented with a pack of Muntons dated 11/16.

 

[ScrewyBrewer]

Their are people who claim 10% yeast loss per month and people who claim it is only 1% per month (properly refrigerated). Guess which group of people sell yeast.

I am not trying to promote my lazy man's method as being better suited to everyone. Over the years, I have managed to propagate and brew beer for a year using the same 'house' strain. But more recently, I have been using less expensive dry yeast instead of liquid yeast, which is a lot more costly and challenging for me to get during the Summer months.

 

[Upstate12866]

I am still using some yeast I bought in 2018 or perhaps earlier, airmailed from the UK during July heat. I recall being very anxious because I had to work and the dry yeast sat in my mailbox all day in 95 degree weather. Then a few packets sat in the fridge for years on end. They still do fine. I tore into a foil pack of Saison last month for instance, and it did fine. 1/2 a pack in a 2-3 gallon batch is my proportion. I have found the dry yeasts to be quite hardy--I don't typically make starters or oxygenate my wort or do much at all to help the yeast. I then save the slurry and reuse 3-7 times. My general outlook on brewing is close to the sentiment described in Brewmeister's comment, mainly because I have not been forced to change that assumption so far. Note that I do not make the best beer, but I do make beer almost every time.

 

[Brewski_59]

One of my favorite things to do is get yeast from the LHBS that's after the use by date at a discount. As long as you build it up with a starter its fine. As my partner always said, you just need one cell to rebuild.

 

[IslandLizard]

I am still using some yeast I bought in 2018 or perhaps earlier, airmailed from the UK during July heat. I recall being very anxious because I had to work and the dry yeast sat in my mailbox all day in 95 degree weather. Then a few packets sat in the fridge for years on end. They still do fine.

Dry yeast is much more resilient than liquid yeast. As long as the granules stay dry.

Unopened packets of dry (brewers) yeast can last many years (5+), especially when frozen or refrigerated. I keep (pound bricks) of baker's yeast stored in the freezer, well sealed after opening, for years without any negative effects.

Liquid yeast, however, is a whole different story...
But I've successfully revitalized liquid yeast that's over 5 years old, stored in the fridge.

 

[shoengine]

Dry yeast is much more resilient than liquid yeast. As long as the granules stay dry.

Unopened packets of dry (brewers) yeast can last many years (5+), especially when frozen or refrigerated. I keep (pound bricks) of baker's yeast stored in the freezer, well sealed after opening, for years without any negative effects.

Liquid yeast, however, is a whole different story...
But I've successfully revitalized liquid yeast that's over 5 years old, stored in the fridge.

It's funny that in the baking world they suggest tossing open yeast after merely months.

 

[deuc224]

I had a 6 month expired wlp 530, and for those who have worked with that yeast know its takes days to grow. This packet took 7 days to come alive but still worked perfectly. Yeast is some resilient stuff.

 

[IslandLizard]

It's funny that in the baking world they suggest tossing open yeast after merely months.

In that light it might be just as funny to note that last Friday I baked with dry yeast (from a previously opened and resealed pound brick, stored in the freezer since bought) that is over 7 years old (M June 22, 2014). This took place on an outdoor camp, heat for rising provided by... sunlight.

Confident it would be active as usual, I did not proof it beforehand. Just sprinkled the weighed amount into the wet batter, then mixed it in. No issues whatsoever, it performed as it always has, rising the dough quickly and perfectly with the right texture and later again after adding 40-50% of weight in raisins and some finely chopped up dried fruit.

The last time I used that yeast must be at least 3 years ago, and it had been opened well before that. Haven't baked with yeast since, come to think of it. I promise to be better with that in the next 3 years, I miss baking breads, pastries, and such.