Tiny magic things, yeast adventures

I’ve talked to a fair few home brewers over the last two years. Pretty much all aspects of brewing have been discussed. One thing that comes up every now and then is the use, growth and reuse of yeast. Something I’ve mostly avoided, until now.

Since day one of homebrewing I’ve used dry yeast. And, up to only earlier this year I’ve pitched it into the wort dry. Since then I’ve done some rehydration of yeast. And even a couple basic yeast starters. Nothing serious.

Off the back of the Pseudo Lager I wanted to capture that yeast. It was a basic US-05 yeast that did what it shouldn’t have been able to do. It took a strong pale ale extract brew and brought it down to a low 1.006. That’s around the lowest I’ve ever got a final gravity. But what was exceptional was that it did it over a period of a month. All the while temperatures ranged from as high as 14°C down to 0°C, maybe lower. I remember one professional brewer saying that the beer was probably stuffed. Yeast being “turned on and off” is not a good thing, by all accounts.

So, these magical tiny organisms had not only survived, but produced some pretty good beer. Could I get them to make more?

I looked up how to reuse yeast. And there are a few ways. The simplest is to pour new wort directly onto the yeast cake, once bottling of the last beer is done. This is a crude method as you’ve got all the dead yeast and left over hops as well. That not-good stuff is called trube. I say not-good because I haven’t come across anything yet that says it’s specifically bad for the beer.

The next method is referred to as washing. Again, you need to get the yeast after bottling. But this time you don’t have to, and can’t, use it straight away. You’re suppose to pour in some pre-boiled then chilled to room temperature water into your fermentation vessel. Boiling is important because you want water without oxygen, or as little as possible, and the heat should kill anything bad. Then you want to chill because heat kills yeast. Once at temperature dissolve the whole lot in the water and pour into sanitised vessels. These should have some kind of air seal as you don’t want any more oxygen. Put in fridge and wait for the cloudy stuff to settle. At the end there should be clear-ish water/beer at the top, a thin white layer if yeast, then a thick bottom layer of tan/brown coloured trube.

There’s a bit more to it, as I came to realise when I did that with the yeast from the Pseudo Lager. Long story short, I had to throw it all out.

Pale Trial Zwei - empty carboys

Pale Trial Zwei to fill these empty carboys

And that brings me to the last brew a couple Sundays ago (31 August). The Pale Trial Zwei was almost the exact same as Pale Ale Ein, but with Galaxy hops replacing the Victoria Secret hops.

  • 14 litre boil
  • 1.5kg Golden LME @ 40 mins
  • 15 grams Galaxy hops @ 30 mins
  • 11 grams Galaxy hops @ 15 mins
  • 1.5kg Golden LME @ 5 mins
  • 12 grams Galaxy hops @ 0 mins

Gravity came in at 1.047, less than Pale Trial Ein. That’s somewhat expected a there was more water in this by the end to dilute the malt.

And then pitched the wort onto the yeast cakes of Pale Trail Ein.

So, this experiment is to see if this can work as a successful way to reuse yeast. Plus want to see if yeast characteristics from one brew can carry over to the next. This second part is going to be the most interesting as the five Pale Trial Ein beers are different in colour and flavour.

Bottling will be next weekend. Look forward to letting you know how it turned out.


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6 thoughts on “Tiny magic things, yeast adventures

  1. Nico Guba says:

    1.006 FG sounds great but what was your starting gravity? The term we are looking for here is apparent final attenuation. Apparent, because the alcohol created during fermentation will affect your reading (it’s not pure water).

    Irregularly propagate my yeast – but it’s liquid yeast. It’s more expensive (6.5 quid) but it’s ok to re-use it about 5 times for lager.

    I find the subject of yeast fascinating, the handling of which has a huge impact of my results.

    Why not try out a vial of liquid yeast? When Harvested at the right time it produces great results and there is a lot more choice available 🙂

    • mikey says:

      Thanks for the comment.

      Original Gravity was 1.049, and with US05 it should have god down to 1.006, and did. That’s a yeast attenuation of 75.

      The issue I was having prior to this, and still have, is that I wasn’t hitting the attenuation of any yeast I was using. Maybe I wasn’t pitching enough yeast, maybe not enough oxygen. I suspect it’s something to do with my water quality, but haven’t done any proper tests.

      Very tempted to start using liquid yeast. Will need to work out how to store it, as I’m mostly doing small batches and don’t need a full packet / vial of yeast.

      I might continue with this yeast harvesting and re-try washing next.

      • Nico Guba says:

        Vials are for 5Gal/20l batches – which are most common for home brewers. For lagers one needs to start with a little more when doing cold fermentation (I do them at 7C-8C).

        It’s really important that the yeast grows fast during the first phase of fermentation. For this it needs to have enough nutrients and the right amount of oxygen present. I regularly hit 80% attenuation but I could improve on the O2 side a bit… Attenuation levels of 83-85% are regularly achieved by pros…. For bright and full bodied Bavarian Helles, these attenuation levels are pretty important.

        I doubt the water quality matters too much in this case. Overpitching is not a good idea either. Chris White wrote a quite accessible book about this topic.

        Hope this helps && Happy brewing!

      • mikey says:

        Thanks Nico, that does help.
        Looks like I’ve got a lot more to try out. Looking forward to it!

        Got a bit of reading to do before I have another go. And have to set up a system to ferment at those low temperatures.


  2. thanks for an examination of the qualities of yeast.

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