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Reusing yeast - the starter method


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Hi guys, 

Since Lusty is getting anxious about a pictorial walk through of the method I use to harvest and reuse my yeast, here it is ?

Today I made a 2L starter, of which I'll harvest about 800mL once it ferments out and keep for next time. I needed about 200bn cells for the batch it'll be pitched into, and 2L on the stir plate with the ~100 billion viable cells I started with nets 386 billion. The 800mL harvest takes about 150bn cells, leaving around 230bn to pitch. A little over the recommended rate but not a problem.

I boil my starter wort in its flask on the stove to reduce cleaning and sanitizing tasks. The stir bar gets boiled with the wort, as shown in these pictures:

IMG_20180608_133530.thumb.jpg.419d6050c90bca4c288af92aa45dfa5f.jpg

IMG_20180608_140704.thumb.jpg.af42425caa18ecb13d46a5996d3fb4ef.jpg

 

After it boiled for a few minutes I turned off the stove, fitted the foil cap and then brought to the boil again for 30 seconds or so to sanitize the foil. It was then left on the stove to cool down, sort of like no chilling.

IMG_20180608_141203.thumb.jpg.a3e95d9798a9ea713a834692970e093e.jpg

 

When I got home from work, the wort was cool enough for the yeast to be pitched. I took the jar out of the fridge, tipped most of the "beer" off the yeast, then swirled it up and pitched it. It's currently on the stir plate, which will run for the next 24 hours or so. The foam houses the temp probe although I can't get the heating function working for some reason ?

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I'll update the thread when the next part of the process happens.

Cheers

Kelsey

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Nice krausen on the starter after 12 hours. It actually began forming about 2-3 hours after pitching last night. I'll turn the stir plate off about 10 tonight, and leave it sit until Monday morning when it'll be stirred up again to be harvested.

IMG_20180609_104843.thumb.jpg.7f265181cf23fc86c946f29e17a621a2.jpg

Cheers

Kelsey

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I should add, it's probably not ideal boiling flasks on electric stoves. I use the gauze to disperse the heat more evenly to avoid hot spots from the rack thingy that it sits on. My bbq also has a side burner similar to the stove ones, so if the next place has a shitty electric stove at least I can still boil the starter in its flask.

Cheers

Kelsey

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Good stuff Kelsey!

Just one question.

What was the gravity of the wort you used, and does the concentration of fermentable sugars (wort gravity) have an effect on the final yeast cell count achieved?

Thanks for taking the time to take some pics & explain it. ?

Lusty.

Edited by Beerlust
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I used about 1.037 as the gravity; 100g DME per litre of water. Pretty standard for starters unless you're building up from a low cell count, in which case the first step is usually a 1.020 SG wort.

The SG does affect the final cell count, I figure the 1.037 figure is a good compromise between good cell count and good yeast health.

Cheers

Kelsey

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1 hour ago, Smitdog88 said:

Kelsey. 

Is the picture of the yeast jar with some of the beer on top. Is that the amount left after tipping some out. Or more to tip out then swirl up. 

Cheers. 

Andy. 

That's what I left behind to swirl it up, that yeast compacts well so it takes a bit of dislodging. Easier with a little more beer left behind. 

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On 6/9/2018 at 2:23 PM, Otto Von Blotto said:

I should add, it's probably not ideal boiling flasks on electric stoves. I use the gauze to disperse the heat more evenly to avoid hot spots from the rack thingy that it sits on. My bbq also has a side burner similar to the stove ones, so if the next place has a shitty electric stove at least I can still boil the starter in its flask.

Cheers

Kelsey

Hey Kesley

My Erlenmeyer works fine on my electric stove hot plate. I am not aware of any potential issues. 

 

Cheers

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They're not really designed for it. They're actually designed for Bunsen Burners. Direct heat like that can stress the glass and weaken it leading to it cracking. Thats why I have the  gauze for the gas burners. It's up to the individual if they decide to do it or not, I just wouldn't recommend it is all. Another some use is to put the flask in a pot of water and boil it that way. Not sure how effective it is though. 

Edited by Otto Von Blotto
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Jeez the edit window is short... Anyway, from a bit of reading it bssically depends on your stove. Straight onto coils isn't good, but you can use a frypan or something between the flask and the element to evenly disperse the heat. If you've got ceramic plates or glass covering the elements then you're sweet.

Cheers

Kelsey

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1 hour ago, Otto Von Blotto said:

Jeez the edit window is short... Anyway, from a bit of reading it bssically depends on your stove. Straight onto coils isn't good, but you can use a frypan or something between the flask and the element to evenly disperse the heat. If you've got ceramic plates or glass covering the elements then you're sweet.

Cheers

Kelsey

Yep, haven't got the shitty electric stove you speak of above, ceramic tops for me. I never thought that some would still have the relic coils, however I guess if your renting then you get what the landlord is prepared to install and therefore there are probably plenty of old school stove tops out there. 

Cheers 

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Today was harvesting day. The starter was re-stirred for a couple of hours, and the jar was soaked in perc then rinsed with hot water and drained. A short time later it was sprayed out with starsan along with the lid. 

From that point it's about as simple as you can get. I swirled the flask around a bit to knock some of the krausen back down, then simply filled the jar.

This was after stirring before I swirled it up.

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In this picture, the flask then goes into the brewing fridge (currently cold conditioning a batch) to crash chill for a couple of days. Tomorrow that batch will be kegged and the fermenter soaked overnight, fridge left on obviously, and on Wednesday the next batch will go in, and I'll decant most of the beer from the starter and swirl it up to pitch, the same as I did with the jar at the beginning of this thread. No warming up of the yeast takes place in either case, it's just pitched cold into the warmer wort.

As for the jar, it goes into the kitchen fridge and sits there until I use it again, when the whole process is repeated.

IMG_20180611_150245.thumb.jpg.2ee1e799e67253147ebfb1197725272a.jpg

Cheers

Kelsey

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  • 2 weeks later...

Question on the amount harvested.

To start each generation off with 100bn cells, drawing off 150bn cells would allow for deaths in the family and bring it down to 100bn by the time you use it next? Say two months time? Realise you may not kill off a third of the cells but might be something to consider?

Cheers

Captain

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I never aim for a certain amount of cells to begin with. I just work out how many I get in my 800mL harvest and run with that. From my stain testing I found it only dropped about 20% over two months as well, so I've been ignoring the calculator prediction and running with a 75% figure at that time to be a bit conservative. At one month I run with about 85%.

Titan, you're better off using foil on the flask than a stopper. There needs to be oxygen allowed to get in and gas exchange take place.

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