Yeast Inflections

Meet the many critters that give beers their unique voices

by Jason Foster

pints

pintsI love writing about good beer; what beer freak wouldn’t? Even writing about bad beer is often cool — if for no other reason than to warn other beer fans away from crap and suggest superior alternatives.

But sometimes it’s also good to take a step back and talk about the building blocks of beer, because knowing more about something you have a passion for only increases your love of it.

And one of the most common questions I get is, ‘what the hell does yeast do?’.

Most folks get that yeast is what turns the sweet barley juice (called “wort”) into beer. Without getting too science-y, yeast consumes sugar and produces alcohol and carbon dioxide. But not many people have a sense of how yeast contributes to the flavour and aroma of beer.

The first fun fact is that beer pre-dates the recognition that yeast is its active fermentation agent by a looong stretch. Louis Pasteur came to that realization in the 1800s but far before that, brewers thought a much higher power was involved. Earlier societies thought it was the hand of God — leading to the phrase “God is Goode” to describe the magical transformation.

Second, not just any yeast works. Beer yeast is the product of centuries of evolution and selective husbandry by brewers that have made it ideally suited for producing what we appreciate in beer.

Beer yeast is actually two species in a large genus that includes bread, wine and spirits yeasts. Those two species create the primary families of beer: ale and lager.

Ale yeast prefers warmer temperatures and produces more fruity esters and other flavour qualities to create a fuller body. Lager yeast prefers cooler temperatures and can eat more forms of sugar, producing a cleaner and crisper beer, all other things being equal.

Want to isolate the flavour and aroma effects of lager and ale yeast? Get a bottle of Hop City’s Barking Squirrel Lager and a bottle of Tree Brewing’s Thirsty Beaver. They have similar malt bills and hopping regimes, and both are malt-accented, amber-coloured beers, so the main flavour difference is due to the fact one is a lager and one is an ale. Here’s betting you’ll find the Squirrel cleaner and more direct in its malt sweetness, with a finish that quickly dissipates. The Beaver will seem more complex, with some fruitiness in addition to the sweetness, and its flavours will linger after it’s gone.

Most of those differences are due to the different species of yeast used. And within each of these species there are dozens of varieties, each producing their own combination of flavours and aromas. Some are clean and neutral; others produce silkier, sweeter beer. Still others accentuate bitterness, while still more bring out particular spicy or earthy flavours.

Are you a fan of Hoegaarden or Blanche de Chambly? These light, summery wheat ales are excellent examples of Witbier, a style defined in large part by its special strain of yeast. Sure, the wheat makes for a softer body and the tell-tale haze, but the yeast is the flavour workhorse. Wit yeasts draw in citrus, light spicing and a zesty flavour and aroma to the beer. It’s the yeast that separates them from North American wheat beers: the little critters produce esters that sharpen and accent the floral, citrusy character of the beer.

The same goes for your favourite Hefeweizen. Because they’re both wheat beer, a lot of people confuse the two styles, but the two different strains of yeast produce very different flavours. In the case of weizens, the yeast used produces clove, banana and even bubblegum flavours and aromas. The beer has a similarly soft wheat base, but the yeast takes it in a very different direction. (Take Blanche de Chambly and put it beside Erdinger Weisse, or even Maisels Weisse: the base beer is very similar, so the difference you taste is due almost exclusively to the yeast.)

The beers that are most defined by their choice of yeast are Belgian ales. These beers are famous for their funky, spicy flavours. Belgian ales start life as regular light or amber ales, but it’s the yeast that gives them the 90-degree turn into the amazing, complex beers that they end up as. Sure, they’re also higher in alcohol, but that isn’t what makes them special. Belgian strong ales have a distinct peppery, musty, medicinal note to them. What did your last La Fin Du Monde or Maudite taste like? Unibroue brews classic Belgian strong ales, and that funky complexity is solely due to the special yeast strain they use.

Yeast is more important than most beer drinkers appreciate. So the next time you tip a pint, give a cheers to the little single-celled microorganism that created it for you.

2014-05-15