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Re-using yeast from previous brew batch

peterlonz

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Sep 21, 2010
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Hi,
I am pretty sure this topic has arisen before but I can't find the thread so:
A couple of days ago I considered I had a low cost opportunity to check how well a re-use of yeast would work, sourced from a just bottled fermenter of Guiness style stout.
The reason for considering this in the first place was that I had two very old & well outdated dark ale kits. (Best before Nov 2006 !!!!!!)
I opened the kits & tasted the malt which seemed OK but a very rapid start would clearly be ideal here.

I managed to collect two 1.25 litre bottles of lees from my fermenter.
I knew the stout tasted as it should so no infection, everything is looking good.

Added one 1.25 bottle of lees direct onto my dark ale wort at 26 Deg C (had to cool with pre-cooled water - Australia !!!)
2.5 hours later we have the beginnings of rapid fermentation, which has proceeded for 24 hours now, overpowering the airlock which has needed cleaning every few hours.

I may not know for sure with a taste test in a few days, whether this has been a sensible act or heresy.
The very old malt extract is said to create a slight metallic taste, BTW, so that alone may mask the answer I seek.

I know that boutique breweries are meticulous about yeast sourcing, cleaning, & preservation but I have never been able to establish what they actually do.

May I ask for comment upon this whole subject, but specifically the pros & cons of doing what I just did & how it might be done better (with new extract of course).
 
Maybe some of our pro brewers will chime in here, But it sounds like your process was right. I regularly reuse yeast this way. Usually using the first beer as a starter for a really big beer. The outcome is you have enough yeast to do the job at hand. However if you have an infection you spread it to more than one batch.

As far as the yeast goes I'm an admittedly an amateur. For preservation (Up to 1 year), I have slants of some of my rare yeasts that I have proofed in petri dishes. It is really not that hard, just takes time and some simple equipment. I think I have about $50 in my equipment. I know that there is a yeast "wash" kit that uses some special acids and chemicals that you can buy, but that is for "LARGE" quantities of yeast. It was not cost effective for me as a home-brewer to use.

Let us know how that 4 year old malt tastes! I'm curious to hear your thoughts on the beer it produces!

Cheers
Preston
 
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