Beauty and The Yeast
Yeast is something of a black box to most beer lovers, and even to many amateur brewers.
Wednesday 06 December 2017
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Yeast is something of a black box to most beer lovers, and even to many amateur brewers. We know it’s the clever little sugar-loving micro-organism that excretes alcohol, and that a ‘Belgian’ yeast will impart a different character to a ‘US’ yeast, but quite where these naturally-occurring beasties come from (and why they’re so good at the specialised task we’ve given them) is a mystery to most.
Whatever you’re brewing, you will most likely be looking for one fundamental thing from your yeast: consistency. Brewers want their yeast to behave the same every time they brew, in terms of its efficiency, attenuation, and how it reacts to environmental factors such as acidity and temperature. And if there’s one thing that doesn’t generally lead to consistency, it’s mystery.
The challenge is that yeast is a living organism and can be sensitive; healthy yeast will perform quite differently to unhealthy yeast, and can even become stressed under the wrong conditions, with a noticeable impact on the finished beer. Many of the off-flavours so loathed by beer pundits are the result of yeast cells that, for whatever reason, are off their game.
In practice then, there is a truly phenomenal amount of work that goes into ensuring that little sachet or vial of beige microbiotic life reaches the wort in peak condition. This work is carried out by developers like Montreal-based Lallemand, which has an almost 100- year history in yeast and bacterial development for food, drink and nutrition products.
While its involvement in brewing only began in the ‘70s, with the production of ale yeast sachets for inclusion in homebrew kits, it now has a broad range of 12 dried yeasts, which range from a standard English ale yeast, through a classic Bavarian Heffeweizen yeast, right through to a champagne yeast for secondary fermentation. It’s currently diversifying into even more specialist and flavoursome strains though, starting with its newly-launched yeast for East Coast-style ales.
In 2002 it also acquired AB Vickers, a venerable producer of clarification agents and production aids, and later Chicago’s Siebel Institute, one of the most prestigious brewing schools in the US. Many commercial-scale breweries will maintain their own ‘house yeast’ – a culture that is kept fed, healthy and growing for pitching into brews as and when it is needed.
Such yeasts are generally robust and versatile strains, suitable for use across the core range. As the craft beer movement has matured though, and consumers’ tastes have broadened to styles such as wheat beers, saisons and west coast IPAs, brewers have had increasing need for specialist yeasts to achieve the required character. This is generally where they will turn to dried or liquid yeast, ready for pitching.
There’s no need to keep a live culture going for occasional brews; instead the supplier has essentially done the work of propagating the yeast for you, and packaged it in a form where it will perform perfectly as advertised, right off the shelf.
When purchasing their yeast, brewers have a choice between liquid or dried form. Dried yeast tends to be more stable, not requiring refrigeration, though historically liquid yeast has often been healthier and available in a wider range of strains.
Robert Percival, regional sales manager for Lallemand, says: “In the past there’s definitely been a stigma against dried yeasts as being inferior, because the drying process is quite aggressive and can be stressful on the yeast. But really that’s quite an outdated view and we’ve certainly seen that perception change among the craft brewers. Technology has moved on a lot, and the quality specifications we have for dried yeast are really tight – tighter than for liquid yeast in many cases. So we have a much greater range now; they’re not all easy to produce of course, but we can do it.”
But where do these yeasts come from? Generally they start out as part of an existing culture collection; repositories of hundreds or thousands of yeast cultures maintained by research institutions, independent microbiologists or companies like Lallemand. Through partnerships, these organisations give each other access to these collections, in exchange for a commercial consideration if any of the yeast samples eventually make it to commercial production.
Identifying a potentially successful strain is only the start of a development process that can take years though, as Robert explains: “Generally we’ll identify a strain that’s of interest and send it to our research and development lab in Montreal. First they’ll isolate just the specific strain they want – because sometimes it might be contaminated with other things – then they’ll grow it and bank it into a yeast bank. Genetic stability tests are very important to make sure the genetic profile is robust and won’t shift over time.
“Once that is confirmed, they’ll start doing various trials to look at how it performs under different conditions; they’ll do fermentation tests, to look at the performance and how it grows. They’ll essentially mimic what propagation would be like for production. Then once those tests are done and confirmed we’ll do some production trials with it. After production trials, we need to do a lot of quality control – as I said, brewers need to be able to rely on the consistency of this yeast absolutely. And then, as we’re currently doing with our forthcoming New England strain for instance, we’ll find commercial partners to work with.
The focus is very much on working intimately with brewers around their specific requirements
“As well as fermentations in the lab, we also do extensive test brews with the Siebel Institute, which give us a thorough analysis of how each strain will work on specific styles. That data gives us on the customer-facing side a really good idea of how it will behave in real-world brewing use, as well as allowing us to iron out any idiosyncrasies.”
Robert says this “real-world” testing and commercial collaboration are important elements of the yeast development business. The perception that many of us have – of white-coated lab geeks locked away in secretive development processes – isn’t accurate. Instead, the focus is very much on working intimately with brewers around their specific requirements and practices.
“I have a brewing background, like a lot of the guys you’ll find in technical sales, and I see a big part of our value as the ability to work with brewers to push the industry and products forward,” says Robert. “We’re really fortunate to have a lot of great breweries willing to work with us. I think that’s as much as anything to do with the collaborative, forward-thinking nature of craft in general. You say ‘does anyone want to trial this?’ and instantly get your hand bitten off.
“We also need to be out in the market, working closely with customers to find any new exciting things, and getting samples to the team in Montreal if we think there’s going to be any interest or value in that longer term. It’s really up to technical sales to get excited about the trends and what’s out there. With the craft brewing movement going at such a pace that’s quite difficult. We’ve been quite lucky that over the past 12-18 months we’ve invested a lot of R&D into areas that have turned out to be really hot.”
One of those areas is freeze-dried bacterial strains for sour beers. Robert recalls going to CBC in the US two years ago, and being astonished to see brewers sitting in the aisles for a presentation on souring bacteria from White Labs’ Kara Taylor.
“This was at a time when sour beers in the UK were really not taking off; we had Wild Beer Co and Chorlton starting to specialise, but it was nothing like it is today, and certainly nothing like America,” continues Robert. “I saw a thousand brewers hanging on Kara’s every word, and knew this was going to be a trend. We already had bacteria products for wine, probiotics and animal feed, so started developing a product aimed at brewing almost straight away.”
Lallemand’s first freeze-dried bacteria product, called ‘Sour Pitch’ is a strain of lactobacillus for kettle-soured beers. There are countless strains of this particular species of bacteria – generally known for its soft, fresh, clean sour character – each of which ferments at a different rate, producing subtly different characteristics under different conditions. After working closely with a clutch of UK breweries known for their kettle sour expertise, as well as conducting a full battery of empirical and sensory evaluations, Lallemand selected a strain called Lactobacillus Plantarum.
“A lot of these bacteria ferment very slowly, which isn’t ideal in a commercial brewing environment, so we looked at that and weighed it against other factors like lactic acid production versus acetic acid production,” he says. “For the majority of sour styles being produced in the UK, we wanted something that would be fast-fermenting, while keeping acetic acids very low, as these cause a pronounced vinegar character.”
Much of the effort now going into the development of brewing bacteria is focused on removing the perceived difficulty and unpredictability of sour beer production, through the same kind of intensive research and quality control that is applied to commercial yeast production. But this same work will also give brewers greater understanding and control of their bacteria, helping them develop new techniques and leading to greater nuance and complexity in their sour beers,” argues Robert. “If we look at some of the strains that didn’t sour very quickly or efficiently, we still start to see some really interesting complementary notes coming through. So, at 20 degrees you might see these green mango notes which in practice really complement hops.
“That’s how I see things going in terms of the wider project – we have these fast, efficient, reliable strains that will give you a good base for sour beer. But then we can start to add these more special characteristics from other strains that give the brewer a palette to work with. We don’t want to create a homogenised ‘sour’ flavour. We want to be able to combine x, y and z and allow brewers to be really creative.”
Then there’s the question of how different yeast strains interact with wort soured by different bacteria, and which combinations produce interesting and desirable results. And this is before you even get into ageing, spontaneous fermentation and other non-kettle souring techniques. Robert concludes: “Whether it’s yeast or bacteria, there’s still so much to learn. And it’s not just about developing new strains – it’s about characterising how the strains we already know about behave under different brewing conditions and how they interact with other ingredients. We’ve only just scratched the surface, but thanks to the craft movement there’s now a real appetite to ask these questions in search of new experiences for the drinker. I’m confident we can take a lot of the mystery and chance out of using specialist yeast and bacteria, while finding new, more complex flavours.”
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