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Yeast Unleashed

Yeast Unleashed

By Greig McGill

Many of us as homebrewers can get locked into our ways. We can be slow to embrace new advances in technology, or new science which might shake up our conceptions of how we can or should do things. It’s understandable - we’ve made something delicious, why would we mess with it? That’s a perfectly valid response. After all, people have been making tasty beer for thousands of years without caring too much about the science behind how it all works.

Still, science can bring more tools to the toolshed. One of the coolest new tools available is the recent advance in genetic sequencing and experimentation with our single-celled beer-making friends, yeast.

We’ve long chosen yeast for their flavour profiles - a spicy and phenolic Belgian strain for our Tripel, a fruity little number for our English Best Bitter, a clean dry fermentation maven for our West Coast IPA, etc. New yeast strains are going above and beyond this though, producing flavours more typically associated with hops, and allowing acidification of wort without needing to apply a kettle-souring process. That’s a game changer, when you think of the possibilities!

I’ve been experimenting with a couple of these new yeasts at Brewaucracy lately, and it’s really opened my eyes to what is possible. I thought it might be helpful to share some of this experimentation with you in the hopes that it helps take your brewing to a new place, or shake you out of a brewing rut. Honestly, it’s like discovering a new colour to paint with!

LalBrew Verdant IPA yeast from Lallemand

Sourced from the Verdant Brewing brewery in Falmouth, Cornwall in England’s beautiful West Country, this house yeast began life as Wyeast’s London Ale III strain. That strain was itself sourced originally from Boddingtons from Manchester, not London at all!

Verdant Brewing are known for their hazy New England IPAs, and that is certainly what this yeast excels at producing. Indeed, try getting this yeast to NOT form a stable polyphenol haze! It’s almost a “cheater’s yeast” for the style. Here at Brewaucracy, we created the latest version of our NZ Pale Ale series, Panic Buy (Jade Sauvin) using no typical “tricks” used in the production of hazy beers. I used no adjunct grains, just the usual malted barley grist. I kept my sulfate:chloride ratio favouring sulfates, as I usually do for this beer, and I used my usual kettle fining regime. I did not use any other finings, and I only coarse filtered the beer, but I was still left with a stable suspended haze which is still defying gravity after five weeks now. It has some of the creamy mouthfeel often associated with high-adjunct hazies, and has that same slightly fruit-juice like character typical of the style also.

The initial stages of fermentation were when I realised this yeast was different! The smells thrown off during the extremely vigorous fermentation were amazing, kicking out loads of apricot, and peach fruity notes, as well as a subtle hint of vanilla. The finished beer, before ANY dry hop had been added, gave notes of apricot, with undertones of red apple, citrus, and tropical fruit. Note that almost all of this character was from esters produced by the yeast itself during fermentation.

Performance wise, the yeast is slightly less attenuative than Chico (US05, WLP001 etc) so leaves a little more body than these strains. This strain flocculates quite well, leaving a good amount of slurry for collection and repitch if desired. The people at Verdant say it also top-crops well, if that’s your jam! We’re not really set up to do that here at Brewaucracy, so I stuck to my usual cone harvest.

If, unlike me, you want to go all-in on a haze bomb with this, a low temp whirlpool combined with protein source like flaked oats will create an even more stable permanent haze which will have a much fuller effect on the already quite creamy mouthfeel. You would also probably want to use the typical higher chloride:sulfate ratio to accentuate the sweeter character of these styles, and add to the fullness of the mouthfeel.

Vicinyl Diketone (VDK) production is extremely low, and while I still highly recommend the usual diacetyl rest be undertaken after fermentation is nearing completion, this yeast is a lot more forgiving in that area! This also assists with minimising the effects of hop-creep, though again, I still recommend doing all you can to avoid this as you normally would.

Lallemand claims this is a very versatile yeast which will suit multiple styles, and while I agree in theory in terms of the flavour profile being good for both hop forward and more malty styles, the haze, fruity aspects, and fuller mouthfeel could be problematic in many styles. Experiment away though, I happen to know where you can buy some!

Wildbrew Philly Sour yeast from Lallemand

You really have to give it to Lallemand - they are really thinking outside the box when it comes to yeast. This one in particular has a very cool backstory, and if I’d been a bit more organised when writing this article, could have made a great Halloween story!

Developed by Dr. Matthew Farber at the University of the Sciences in Philadelphia, Pennsylvania, USA, this particular strain was actually sourced from a tree in a graveyard in West Philadelphia! Spooooooky! It’s also, unlike most brewing yeasts, not a part of the Saccharomyces family. Philly Sour is a species of Lachancea and is interesting because as well as fermenting sugars into alcohol and CO2, it also produces lactic acid, negating the need for kettle souring in beers like Berliner Weisse or Gose. What a neat trick!

It’s a little more finicky to use compared to most brewers yeasts, but I can confirm that it does produce a beautiful and complex sourness, more so than I’ve ever achieved by kettle souring alone. I was very impressed with this yeast, and am excited to see how other brewers use it in the future.

To get the most from Philly Sour, you’ll need a nice easily attenuated wort - mash low, between 64 and 66C. There’s no real need to target any specific mash pH beyond the usual 5.2-5.5 range, so do what you normally do depending on what you’re trying to achieve there. For optimum lactic acid production, you will want to add around 2% glucose/dextrose to the wort (you can do this in the kettle). You will also need to ferment quite warm - Lallemand recommends between 22 and 25 degrees Celsius.

This yeast does work more slowly than Saccharomyces strains, and most of the acid production is done over the first 4-5 days, and you’d expect to hit your lowest pH after that time, with fermentation completing fully after another 4-5 days. To give you an idea, I hit terminal pH of 3.2 (down from 4.9 at pitch) after 4 days, and fermentation was done after a further 4 days, at a pitch temperature of 23C rising to 25C terminal.

I highly recommend having a play around with this yeast, as it’s a truly innovative addition to your brewing arsenal, and yes, I know where you can get this one too!

What else is out there?

This is getting a bit wordy, but I am genuinely excited by the possibilities afforded to the brewer by advances in yeast technology. Yeast strains are already being developed which have all sorts of special traits. Some purely designed to optimise existing functions - bigger, better, faster, more - and some to do unique things like reduced VDK production, production of esters and other flavour compounds, breakdown of previously unfermentable starches, clarification of beer, and more. The future is bright and yeasty! Ain’t technology cool?