Old Slope

[nallum]

I found a box of old yeast slopes. They’ve been stored at room temperature for at least 3 years by mistake and were meant to go in the bin. A couple had a few very large (old) surviving colonies. What a great natural experiment! What allowed these few colonies to survive? How are they different? Is it just the expected statistics of a few colonies surviving after all this time?

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I prepped an overnight culture and compared it with the same yeast stored for about the same period on cryobeads in the freezer. There was no growth from the cryobeads, but loads from the old slope.

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[IPA]

The ability of yeast to survive,despite us, is amazing. I have found viable yeast in old bottles many times. The record for me were some bottles from 1977 which had been stored in less than ideal conditions and moved several times in the UK and finally here to France. They were coaxed back to activity in 2010. Thirty three years later !!

[nallum]

Definitely, in the perfect medium, like beer, yeast can survive for many decades. But not so long on slopes, even though slopes are the best format in Brewer's time. I'm going to plate out and select some healthy-looking colonies for a starter then I'll make a half batch of Bitter to assess things.

[nallum]

Selected some healthy looking yeast colonies to inoculate an overnight culture for fresh slopes.

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[IPA]

Looks like my favourite yeast. Commercially available as WLP 037

[Cobnut]

It is a yeast I’d like to try, but brew schedule is full of other beers for several months, so little point in buying a pack of this yeast even if it were available ( I believe it is one of the seasonal releases).

[nallum]

Yes, got some WLP037 freshly prepped. One of my favourites too. Along with Harvey’s and WY1469. I got a bit bored playing with Verdant’s strain. It’s not bad but gets a bit too ‘peachy-vanilla’ for my taste/beers. I’m looking forward to getting back using these other strains. All much better, imo.

[nallum]

Decided to go with Harvey's first. I think it's been a while. I let the overnight mini (10ml) starter carry on culturing until finished and got a nice layer of sedimented yeast after a couple days. So got out some pre-prepped frozen starter wort to thaw. No hurry. Just left it sat there until at room temperature.

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Stepped up and let it do its thing.

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Done and now flocculating very well, which is a good sign it's behaving itself.

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Time to thaw some more starter wort...

[nallum]

Just let it thaw and come up to room temperature.

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It's only a yeast starter.

[nallum]

Now it just needs to be left alone for a couple days to do its thing.

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[nallum]

Good grow overnight. It still appears to be behaving like a good top cropper with yeast flocculating on top and bottom leaving relatively clear wort in between.

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Gave it a swirl to knock out excess CO2 and get yeast back in the starter wort.

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[nallum]

It’s winding down this morning with final flocculation in progress.

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Ideally, it should be pitched today without any chilling. Or certainly within a few days after being stored cold in the fridge. Regardless, at this stage, I’d let it carry on at least for the rest of the day day, until completely sedimented. Letting it sit there for 72h/3d isn’t a problem, but I’ve already got a mash going so it’s getting pitched today.

[nallum]

I pitched the 600ml high vitality starter into 20L, which is going to be plenty to fill my pin cask. Fermentation got delayed after my impatience late in the evening decided to pitch the yeast starter into wort that was over cooled by mistake. The difference (14*C vs room temperature) shocked the yeast a bit. But they recovered and were rocking well before 24 hours. Now starting to climb out of the FV:

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Smells great. So all looking good so far.

[nallum]

Turned out great.

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Fermentation took just over 4 days, probably because I pitched the yeast into cool wort. I missed the opportunity to cask it before it finished. It ended up staying in the FV for a few more days. Attenuation was 85%, but mash was @ 65*C. Could easily go up to 70*C with this yeast, but the aim of the brewer is to produce alcohol so can’t complain. Used inverted sugar to prime in keg. Got a tad too lively so conditioned for serving overnight. Tastes pretty good now it’s gone bright. The phenolic character has mellowed out into some nice complimentary complexity. I’d say it survived intact despite being left at room temperature for years.

Old WY1469 up next then.

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