A closer look at beer: yeast

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First Posted: 2/25/2014

Yeast is the true unsung hero of the brewing process; after all, without it, we wouldn’t have alcohol at all. Many of us are familiar with yeast in the baking world as, traditionally, baker’s yeast is used to make a wide variety of breads. However, for many home brewers who were attempting to make their own beer around 30 years ago, they were also forced to use baker’s yeast to make their beers.

Thankfully, things have come a long way in the yeast world for home brewers and commercial brewers alike, and we have all benefited from these advances greatly with a variety of tasty beers.

While many may have a faint understanding of yeast, many do not know what it does to the beer and how it actually works. Once a brewer has finished boiling his wort (unfinished beer), he pitches yeast into it and this is how it ferments and becomes alcoholic. The brewer knows it is working when a large foam begins to appear on the beer; this is CO2 coming to the surface.

In the crudest way of describing it, this happens by the yeast cells eating the sugar and pooping out alcohol. In ancient days, this was not fully understood and many viewed this process as “magical” and “God’s hand at work,” as brewers did not directly pitch in yeast; instead, the yeast was wild and blowing through the air and landed in the beer and started the fermentation process or was on a stirring stick, unbeknownst to the brewer.

Yeasts are broken down into two main categories: bottom fermenting and top fermenting. The differences are subtle, but very important. Bottom fermenting yeasts and those that take longer to ferment and are much more temperature-dependent, as they work best at colder temps (41 to 50 degrees Fahrenheit) and are traditionally used in many German beer styles.

Top fermenting yeasts are those traditionally used in ales and can ferment much faster, and while they are also temperature-dependent, they have a much wider range they can ferment within (59 degrees Fahrenheit and above).

Yeast strains are vitally important to beers and can impart a huge flavor profile to the beer. Many breweries also have distinctive house yeasts that they repeatedly use in their beers and this gives them their “house character.” Breweries such as Brewery Ommegang and the Cantillon Brewery are prime examples of breweries that have a distinct house character within their beers.

Examining beers with distinct yeast flavor profiles can be difficult for untrained drinkers, but rest assured, we have all had beers with a distinctive yeast flavor. There are some great styles to examine that truly showcase yeast flavors.

Saision/Farmhouse Ale: This style is a prime example of a beer deriving nearly its entire flavor strictly from the yeast. The saison yeast strain gives this beer its distinctive flavor, and many brewers simply stand back and let the yeast do the work when brewing. Some world-class examples of saisons are: Brasserie Dupont, Saison Dupont; Brewery Ommegang, Hennepin; Allagash Brewing Company, Allagash Interlude; and Boulevard Brewing Co., Tank 7.

Belgian Tripel: This slightly higher in alcohol (8 to 12 percent ABV) Belgian style ale has strong fruity notes that come directly from the yeast strain. This is a style that many confuse the tastes and aromas with added ingredients, when it is primarily derived just from the yeast strain. Some amazing takes on this style are: Unibroue, La Fin Du Monde; Allagash Brewing Co., Allagash Tripel Ale; Brouwerij Bosteels, Tripel Karmeliet; Brouwerij Westmalle, Westmalle Trappist Tripel; and Chimay, Chimay Tripel (White).

Many of the styles and beers recommended are also bottle-conditioned, meaning a small amount of yeast was added to each bottle so that the beer continues to ferment, slowly, in the bottle, thus enhancing the shelf life for the beer. However, the very bottom of the bottles should be left behind and not poured into a glass, as the intense flavors can be a bit off-putting to some.

Yeast is the workhorse of the beer and its hard labor pays off each time we enjoy one of these fantastic beers.