Author Topic: Keeping Yeast Slurry Long Term  (Read 2394 times)

Offline pete b

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Keeping Yeast Slurry Long Term
« on: June 03, 2015, 01:21:48 PM »
I have not brewed since April and cannot brew anytime soon. I have a large kitchen renovation/addition project that unfortunately could not happen until spring when I had to get the garden in etc. and then my girlfriends brother died suddenly last week which of course brought emotional trauma and a lot of practical things we need to do to help the family.
I have a lot of yeast slurrys which I normally use successfully as is from the fridge within 3-6 weeks. I have a couple question about using and storing months old slurry. Should I feed them kind of like sourdough starter (but with wort) from time to time? I won't be trying to use them as is, I'll make a starter when I get to them: what's the best method in this case? Use a couple tablespoons and step up? Use all of it (maybe 300 ml) and make directly into a pitchable sized starter? Any other advice?
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Offline brewinhard

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Re: Keeping Yeast Slurry Long Term
« Reply #1 on: June 03, 2015, 01:23:47 PM »
How much yeast approximately do you have saved in each container?  Are these slurries saved from the primary fermenter of previous batches?

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Re: Keeping Yeast Slurry Long Term
« Reply #2 on: June 03, 2015, 03:28:59 PM »
You can store yeast under beer in a sealed container for years as long as your sanitation is good, although at this scale, if you have access to fresh yeast it's probably worth the $7.

Ideally you'd want the beer in question to be 2-3% ABV like from a starter. Don't feed the cultures - it's a contamination point and the whole idea of long-term storage is to keep the cells dormant. When you want to use the yeast just put a couple tablespoons in a starter. Unless it's a large (more than ~2 L) starter I wouldn't worry about stepping up. Some yeast nutrient in the starter can't hurt either.
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Offline Joe Sr.

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Re: Keeping Yeast Slurry Long Term
« Reply #3 on: June 03, 2015, 05:22:27 PM »
I agree with Sean.  I store my yeast in exactly the fashion you are describing and regularly use slurries that are months old.  When they get beyond a yearI will typically toss them but more because that means its a strain I'm not using much than because I worry about sanitation or viability.

Make a starter.  Use a small amount and use some yeast nutrient.

I've found this approach works much better than trying to wake up the entire slurry.

There is no need to feed the yeast during storage and I would not recommend doing that.
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Offline pete b

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Re: Keeping Yeast Slurry Long Term
« Reply #4 on: June 03, 2015, 05:27:21 PM »
How much yeast approximately do you have saved in each container?  Are these slurries saved from the primary fermenter of previous batches?
About 300m and yes.
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Offline pete b

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Re: Keeping Yeast Slurry Long Term
« Reply #5 on: June 03, 2015, 05:33:35 PM »
You can store yeast under beer in a sealed container for years as long as your sanitation is good, although at this scale, if you have access to fresh yeast it's probably worth the $7.

I save yeast so I have a variety around as much if not more than to save money. I don't live near a lhbs.
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Re: Keeping Yeast Slurry Long Term
« Reply #6 on: June 03, 2015, 05:58:13 PM »
I have been experimenting with using the double-drop technique to start slurries that are older than 5 weeks from the date that the batch was pitched.

Here's my process:

1.) Pitch the entire slurry (100 to 150ml of solids) into starter wort
2.) Separate the liquid fraction from the sediment when signs of low krausen appear
3.) Pitch the separated liquid fraction at high krausen 

This technique allows me to capture a large number of viable cells from the slurry while discarding the non-viable cells and all of the remaining break and organic matter.  I have yet to try it with a really old (> 6 months) slurry because it is just as easy to grow a new culture from slant.  A really old culture is going to have lysed cells in it.

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Re: Keeping Yeast Slurry Long Term
« Reply #7 on: June 03, 2015, 06:13:53 PM »
I save yeast so I have a variety around as much if not more than to save money. I don't live near a lhbs.

If I were you, I would look into maintaining a small bank of cultures on slant.  Aseptic technique is relatively easy to learn.

I started plating and slanting yeast back in 1993, so that I could have easy access to a variety of yeast strains as well as brewery strains that were not available via the home brew trade. 

Offline pete b

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Re: Keeping Yeast Slurry Long Term
« Reply #8 on: June 04, 2015, 10:40:30 AM »
I have been experimenting with using the double-drop technique to start slurries that are older than 5 weeks from the date that the batch was pitched.

Here's my process:

1.) Pitch the entire slurry (100 to 150ml of solids) into starter wort
2.) Separate the liquid fraction from the sediment when signs of low krausen appear
3.) Pitch the separated liquid fraction at high krausen 

This technique allows me to capture a large number of viable cells from the slurry while discarding the non-viable cells and all of the remaining break and organic matter.  I have yet to try it with a really old (> 6 months) slurry because it is just as easy to grow a new culture from slant.  A really old culture is going to have lysed cells in it.
how much wort? 1 litre? This seems sound.
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Offline pete b

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Re: Keeping Yeast Slurry Long Term
« Reply #9 on: June 04, 2015, 10:46:38 AM »
Mark, I have been interested in doing this since some of your early posts showing some of your collection. Right now I I'm in a phase of life where I need to carve out some time because I'm a bit too busy. I can picture doing this in a few years.
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Re: Keeping Yeast Slurry Long Term
« Reply #10 on: June 04, 2015, 01:16:42 PM »
how much wort? 1 litre? This seems sound.

I use 1 liter of 10% w/v (1.040) wort and my "shaken, not stirred" technique with a 5L media bottle; however, a 1-gallon glass jug will work.

Note: For those who live in the UK, a 1-gallon American jug is what you refer to as a 1-gallon demijohn.  A British jug is called a "pitcher" in the U.S.

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Re: Keeping Yeast Slurry Long Term
« Reply #11 on: June 04, 2015, 02:05:36 PM »
Mark, I have been interested in doing this since some of your early posts showing some of your collection. Right now I I'm in a phase of life where I need to carve out some time because I'm a bit too busy. I can picture doing this in a few years.

I had to quit brewing for several years due to demands on my time, so I know what you are up against.

With that said, once you get setup and start maintaining your own bank on slant, you will kick yourself for not doing it sooner.  The basic skills necessary to prepare absolutely sterile media and plate/slant yeast are high school-level biology.   

I was basically in the same situation that you are today when I first started to maintain a yeast bank.  At that point in time, anything other canned kits, questionable dry yeast, and oxidized hops was considered to be exotic.  White Labs did not exist, and the Wyeast catalog could be enumerated using two hands.  Many Wyeast strains were difficult to obtain due to the perishable nature of liquid yeast and the relative immaturity of the market.   

With that said, things changed rapidly after 1993.  However, the impetus for that change was not the AHA.  The driving force behind the rapid technological advancement within the hobby was a magazine called Brewing Techniques (compare Zymurgy articles from the same period with those published in Brewing Techniques, and you will see what I mean).  I did not bother to join the AHA during my first pass through the hobby because I did not care for Zymurgy (I still only scan the magazine). While the quality of the articles in Zymurgy has improved greatly over the years, it's still more of an entry level/brewing lifestyle magazine than a true nuts and bolts small-scale brewing magazine. The community needs a modern version of Brewing Techniques.  Neither BYO nor Zymurgy fills the void that was created when the publisher of Brewing Techniques shuttered its doors.  In my humble opinion, the BA/AHA should consider offering a subscription above and beyond the cost of membership technical journal much in the way that the Amateur Radio Relay League (ARRL) offers QEX (the ARRL's lifestyle magazine is called QST).  I would write for such a journal.
« Last Edit: June 04, 2015, 02:08:14 PM by S. cerevisiae »

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Re: Keeping Yeast Slurry Long Term
« Reply #12 on: June 04, 2015, 05:08:19 PM »
I save yeast so I have a variety around as much if not more than to save money. I don't live near a lhbs.

I'm in the same boat. 250 miles round-trip to my "local" homebrew shop. I tend to mail-order new cultures once every year or two, in either the spring or fall when shipping temperatures are reasonable.
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Offline erockrph

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Re: Keeping Yeast Slurry Long Term
« Reply #13 on: June 04, 2015, 05:14:26 PM »
I save yeast so I have a variety around as much if not more than to save money. I don't live near a lhbs.

I'm in the same boat. 250 miles round-trip to my "local" homebrew shop. I tend to mail-order new cultures once every year or two, in either the spring or fall when shipping temperatures are reasonable.
My LHBS is open hours that generally conflict with my work/family schedule, so I'm in the same boat. I keep a stash of dry yeast on hand for short-notice brews, and try to brew a couple of successive brews when I use liquid yeast. For strains I like but can't get a hold of easily, I keep a few mason jars of the yeast cake from a previous batch and store them in the fridge. I've had good luck with most strains just growing up a starter from these.
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Re: Keeping Yeast Slurry Long Term
« Reply #14 on: June 04, 2015, 05:23:29 PM »
I'm in the same boat. 250 miles round-trip to my "local" homebrew shop. I tend to mail-order new cultures once every year or two, in either the spring or fall when shipping temperatures are reasonable.

Two hundred and fifty miles to the nearest home brew supply store?  Man, that's hardcore.

I maintained several cultures in my original bank for over a decade.  I kick myself for allowing a few of the cultures in that bank to expire.  For example, I had the two major strains in real Ringwood isolated on different slants.  I kept Brewtek CL-170 and Brewtek CL-660 alive for most of the time that that bank was in existence much in the same way that Denny kept Brewtek CL-50 alive long enough to convince Wyeast to package it as Wyeast 1450.  I kept Brewtek CL-210 alive for a long time as well.