Some Yeast Questions and Recommendations

[Yesfan]

I've been going through my inventory and found some old dry yeast in the back of my fridge. It's from 2018 (Lellamand Belle Saison, 2 packs). I found an unopened bag of light DME I had bought and forgot about from 2017. I made a small 2L of 1.020 wert, added some nutrient, and the yeast took off in just a few hours! After a couple of days I cold crashed, decanted, then added a litre of 1.040 wert to try to bump it up a little more. I cold crashed and decanted and then transferred to a 2L (cleaned/sanitized) bottle for storage. When transferring to the bottle the yeast smelled bready and sweet.

Have any of you all used a 2L Coke bottle for storing yeast? Seems 2L bottles (or smaller after decanting spent wert) would be a perfect vessel to use for storage. They're taller, non-breakable, and can handle pressure compared to mason jars. I know this may be crude to some but I'm just playing around and see what happens. I've thought about doing a simple smash beer with this yeast to see how it comes out. I'm leaning toward Munich and Centennial to use up some older inventory but open to other suggestions.

On another note, how long can you go on a yeast cake from batch to batch? A couple of months ago, I brewed a 10 gallon batch and pitched 2 packs of US-05. The fermenter was a 15 gallon corny keg. I've not opened it since transferring to kegs so was wondering how viable the yeast would be. That brew was just a small 4.5% pale ale if that matters. Again, I've thought about saving it to just see if I can.

Thanks and sorry for the winded post.

 

[Red over White]

Short term yeast storage in soda pet bottles is OKish. Pet bottles are not impervious to oxygen and they lose their ability to block oxygen with time. Major brands seem to be better than local brands or clear store brand bottles in my experience. Kegland oxebar bottles are currently the king of the hill for storage, but they have a shelf life too and are planned obsolescence, just 4x longer than regular soda bottles (the clock is always ticking). I use a fresh soda bottle once and recycle it.

 

[Jack Arandir]

Re: old yeast cakes:
If the yeast isn't refrigerated and handled well I wouldn't risk repitching. Safale 05 is so cheap it's best to just get a new pack. In the industry harvested yeast is usually repitched within 2 weeks with good handling. An awful lot of breweries aren't harvesting yeast at all and just buying fresh yeast each batch.

How viable is your yeast? Yeast is pretty durable so I'm sure you would get viable yeast cells. You'd also get mutations and stressed yeast that may give off flavors. Better not to risk it.

 

[HighVoltageMan!]

Yeast in storage should be kept away from oxygen as much as possible. When stored yeast comes in contact with oxygen it will force the cell into metabolism by using up it's glycine reserves. Once these reserves are used up, the cell is kaput. Although it may not be sexy, a mason jar with a nice layer of beer is one of the best ways available to homebrewers to store yeast.

The other thing that can be used to preserve yeast for longer periods is a buffer salt added to the yeast slurry. Potassium dihydrogen phosphate (AKA monopotassium phosphate) in a 2-3% solution works very well and can extend yeast storage several months.

Here's a paper written in the late 1940's by an Englishman, Dr. L. R. Bishop. He studied ways to preserve yeast in breweries with simple refrigeration.

https://onlinelibrary.wiley.com/doi/abs/10.1002/j.2050-0416.1955.tb06256.x
Here's a Master Brewers podcast on the same subject.

https://www.masterbrewerspodcast.com/189
I made a German Pils with Wyeast 2124 that was stored for 6-7 months with this method. The yeast just came to life in the starter and the beer turned out excellent.

 

[Yesfan]

Thanks for the replies. The US-05 is in a keg that I used for fermentation. It's currently two months old, at room temp, and hasn't been mishandled. The keg is still pressurized at 10psi. Since I have a couple of packs of US-05, I may just toss the cake, clean the keg, and start anew.

Here's a pic of the Belle Saison yeast. I didn't think of putting a carb cap on it, so when it cold crashed, the bottle imploded a little.




As I mentioned earlier, the yeast took off when I made a starter with it. It didn't smell bad either when I transferred to the 2L bottle. Smelled sweet and bready. The light and dark layers is interesting to see. Is the darker layer dead yeast? The yeast pack was 5 years old.

Truth be told, I have quite a bit of grains that have gotten old. I've thought about doing a batch to see how it comes out. I'm not going to use this older yeast in anything fresh in case you're wondering. I could throw all the older stuff away (probably best), but figured since I have it I could brew and see what happens.