Harvesting Yeast From Bottles : An Illustrated Guide

In an attempt to make my brewing more efficient, continuous and economical I’ve been investigating how to harvest yeast from bottles. Here I explain how to do it.

harvesting yeast after aeration

Benefits of Harvesting Yeast From Bottles

There are several reasons to harvest yeast; perhaps to save money or to use a commercial brewery’s yeast in your home brew.

In general, when reusing your own yeast it’s better to take it straight from the fermenter, because that doesn’t necessarily require a yeast starter.

Harvesting from bottles is mainly useful if you forget to do that, or if you want to resurrect a special yeast from a particular beer. I’m planning to harvest some Belgian yeast later in the year, for example.

The technique works best with medium or weak beers, because high alcohol levels can damage yeast.

How To Do It

Equipment

You need:

  • bottle conditioned beer
  • sanitiser
  • saucepan
  • water
  • malt or malt extract
  • container for yeast (a 2 litre plastic bottle will do)

Process

The yeast in a typical bottle of beer are dormant and small in number. You need to wake them up and encourage them to multiply.

To do this you prepare a yeast starter, which is essentially a mini- batch of home brew.

One approach is to boil dry malt extract in water but if, like me, you enjoy the brew process in itself, you can carry out a mini-mash instead.

To begin, heat 1 litre of water to 63°C in a small pan and add 200g base malt.

yeast starter mash

Try to use a malt that’s similar to the ingredients in your planned recipe. For example, use pale ale malt if you’re going to use the yeast in a bitter.

After mashing (I leave it for one hour) remove the grains and drain, and bring the wort to the boil.

Boiling sterilises the wort so that you can add yeast without fear of infection.

After twenty minutes remove from the heat and put the pan in cold water to cool.

harvesting yeast chilling brew pot

While that’s happening, prepare the starter jar. I use a simple plastic bottle but any 1 – 2 litre, clean container is fine.

It’s essential to sanitise effectively for your yeast to have any chance of survival. Star San is effective.

harvesting yeast sanitising bottle

Now’s a good time to check your beer is to hand.

In their great book Yeast, Chris White and Jamil Zainasheff recommend storing the beer for a week before you need it.

This encourages the yeast to settle out of the beer and form a compact layer on the bottom of the bottle.

harvesting yeast from bottles

When the wort is cool carefully pour it into the sanitised bottle.

harvesting yeast pouring wort into yeast jar

The foam in the photo is from the Star San. You could use a funnel to make pouring easier, but I don’t.

harvesting yeast starter in bottle

Although the foam looks alarming, according to the Star San manufacturers this is harmless and can actually provide nutrients to the yeast.

harvesting yeast sanitising beer bottle

Open the beer. Immediately (before pouring) sanitise the neck and opening. A spray bottle is useful.

Pour the beer into a glass for drinking, leaving the yeast sediment and a little beer in the bottle. Swirl it up and tip it into the yeast starter.

harvesting yeast pouring yeast from bottle

Give it a good shake (with the lid on).

Remove the lid and lightly cover with film. If your fermenter airlock fits use that instead. Gas should be able to escape without letting air and bacteria in.

harvesting yeast finished starter

Leave the starter undisturbed to ferment.

harvesting yeast from bottles : first signs of fermentation

Because it’s such a small amount it should happen quickly.

harvesting yeast krausen

You’ll see a krausen layer build on top and then gradually die down.

The whole fermentation process takes around two days, plus a day for settling,  so you should harvest the yeast about three days before you plan to brew.

harvesting yeast : yeast have settled to bottom of bottle

John Palmer suggests putting the starter in the fridge the day before brewing so the yeast settle to the bottom. Depending on how tasty your starter wort is, you may want to pour it away and pitch the yeast alone into the beer, or just add everything.

With this batch I removed most of the starter, pitching just the yeasty slurry that was left.

harvesting yeast pouring starter into fermenter

The yeast will keep for a few days but after that it may need reinvigorating again with more starter.

You can keep harvesting forever, but most advice suggests that after 6 or so times it’s worth starting again.

This is an easy (and weirdly satisfying) brewing technique – give it a try.

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Comments...

  1. I have been curious about doing something like this. When I’m feeling adventurous, this will most certainly come in handy. Great tips!

    • John

      Thanks!

      I’d definitely recommend trying it out. You just have to be organised and remember to do it a few days before the main brew.

      It could be the yeast starter rather than the reharvested yeast themselves, but I’ve noticed a big improvement in fermentation since I started doing this. The beer now gets down to the expected final gravity much more often.

  2. Chris

    Would it make sense to culture the yeast once you’ve harvested it? It seems doing so would let you hang onto it long-term rather than having to reharvest over and over, and reduce the extremophile population – if you culture it right it could get you back to the original strain rather than primarily the one that survives fermentation.

    • John

      That would be a nice target. However, I haven’t got experience with yeast culturing so can’t comment in much detail.

      Having a pure sample ready for use would be better than reharvesting, for sure. I’m not sure bottled beer is the best place to find yeast though. I guess you’d have to somehow separate out the strains and isolate the good one, if it’s still there.

      If you know more, I’d be interested to hear about it.

  3. Brian

    Any thoughts on reharvesting yeast strictly for bottle conditioning your own homebrew? My concerns are with beers that lager a bit or that I rack; I’m always worried I’ll end up with flat beer.

    I’d like to make a saison using one of Wyeast’s saison culture, then I was thinking of reharvesting the Logsdon Seizoen Bretta when bottling. The Brett would eat some residual sugars and hopefully add a nice Co2 level.

    • John

      Brian,

      Thanks for the question.

      Not having tried that I can’t offer any advice based on experience I’m afraid.

      But I can’t see why it wouldn’t be worth giving it a go. If you make a yeast starter with the dregs from your beer, you’d know whether the Brett was viable or not before committing to a full batch.

      In any case, it’d be interesting to try it out to see how it goes. Personally I don’t mind if these things work out or not – it’s always fun testing.

      Sorry I can’t be more help though, and good luck!

  4. Dan

    I’m on a few day vacation and picked up a case of fresh Jolly Pumpkin. I want to use the dregs when I get home. Think there would be a problem with dumping the dregs in a sanitized swing top bottle and keeping it cold until I get home?

    • John

      That would probably be OK if you’re careful and quick, but it would be better to set aside a whole bottle.

  5. Martin

    Harvesting from bottles is something I’ve done successfully many times, it’s not difficult. The problem with commercial beers is that some add a specific sort of yeast (sometimes wine) for bottling and thus it may not be great for fermenting your batch of home-brew.

    • John

      Thanks!

  6. Kyle

    Thanks for the write up!! I just did this tonight with some wheat dry malt extract and yeast from Oberon ale. I’m trying to make an Oberon clone using this yeast. I was going to add more wort and another batch of yeast from another bottle. Maybe do that again. How will I know if I have enough yeast for my 5 gallon batch?

    • John

      Hi Kyle,

      If the yeast starter works, and shows good signs of fermentation, it is most likely that you have enough.

  7. Adrian Knox

    When fermentation is complete in the Primary,can I then bottle some of the yeast that has settled on the bottom of the fermenter..I suppose there would be dead and also live yeast there..Regards

    • John

      You can. The process is called yeast washing.

    • Adrian Knox

      Thanks John

      I’ll give it a go with my next A/G brew. Sounds good to me. Will certainly save some cost, especially when using the expensive Liquid Yeasts.