Yeast: Beer’s Least Talked About Ingredient


Shawn Meek, Chris McDonald Atlantic Canada Beer Blog

With all of the considerations that need to be made with the basic ingredients of malt, hops, and water, the job of changing it all into beer ultimately belongs to yeast. As someone once said, “brewers make wort, yeast makes beer.” This is by no means taking away from the importance of putting a recipe together for a brew day picking your malt bill, choosing your hops, and tweaking your water all play a significant role in brewing. But if you don’t include yeast, it’s all for nothing. And as any brewer can tell you, yeast can be a supremely wonderful and frustrating organism all at the same time.

People have been brewing beer for thousands of years, but the role of yeast was unknown until its discovery by Louis Pasteur in the late 1860s. Yeast is a type of fungus that converts the sugars of the pre-beer wort into alcohol and carbon dioxide, as well as many other substances (such as esters, phenols, and diacetyl) that give beer its aromas and flavours. Brewer’s yeast is typically known as Saccharomyces cerevisiae (“Sacc” for short), but there are hundreds of variants available to brewers, all of them providing their own unique taste profile to the beer they ferment.

When selecting a yeast strain, there are many factors that the brewer has to consider. For starters, Saccharomyces generally fall into two categories: ale or lager. Ale yeasts are known as “top-fermenting” and generally require warmer temperatures than lager yeast (“bottom- fermenting”). Even within the same family, the aroma and flavour characteristics can vary widely.

An American IPA is best fermented by a mostly-neutral strain, allowing the strong hop character to be the focus of the beer. A Belgian Tripel, however, benefits from a strain that exhibits plenty of fruity esters and spicy phenols, to add character to a beer brewed with a simple grist. Other factors such as how much sugar the yeast will consume during fermentation and the degree to which yeast will drop out of suspension after fermentation are also factors.

Halifax’s Garrison Brewing employs a handful of different yeasts in their beers, depending on the style. “There are a multitude of reasons for using a given yeast strain, but for me,” says Brewmaster Daniel Girard, “the most important factor is its impact on the flavour profile of the beer.”

They use the same British yeast strain for several of their beers, including their Irish Red and Nut Brown Ale, accentuating the malt character of the brew. While this high-flocculating yeast made life easier for their filtered beers, it was a problem for those that are not filtered.

“The issue is that highly flocculent strains tend to form clumps in the bottles over a longer period of time for unfiltered beers. Although there is no impact on the taste profile of the beer, clumps are not appealing visually.” In their Imperial IPA, an unfiltered beer, they’ve chosen a Californian Ale strain of yeast that is clean- fermenting, allowing the generous hopping to shine through, and if the yeast does settle out, will not bind together.

Yeast strains can be extremely finicky creatures, but their role is critical to the brewing process. When treated properly, taking into account aspects like pitch rates, aeration, temperature control and filtration, they can produce some truly spectacular beers.

The harmonious relationship between brewer and yeast benefits us all. 

Occasions Recommends
Garrison Imperial IPA, 650 ml $5.75
Garrison Irish Red Ale, 6 x 355 ml $13.49

Next Week
We put the spotlight on Boxing Rock, a South Shore brewery that has quickly become one of the province’s largest and most respected microbreweries.

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