The brewery cellar at Gahan House (photo: Bryan Carver)

The yeast family

The key ingredient in the brewing process

The Brew | by Bryan Carver

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Last month we took a look at the brewing process and what a brewer does each brewday in order to create wort, the bittersweet liquid that brewers yeast ferments in order to create beer in the brewery cellar. Yeast is the creature that is responsible for the miraculous transformation, a necessity to create beer and a variety of other fermented foods and beverages.

For millennia people were uncertain of what caused this magical change in a liquid, an airy foam that appeared to boil at cool temperatures, changing grape juice to wine and sweet grain based liquid to beer. It wasn’t until the mid 19th century that the study of early biologists, utilizing the newly invented microscope, identified the single cell creature responsible for fermentation. These discoveries changed the way people produced beer, wine and bread, once a reliable source of a mass produced yeast was available assisting them in creating a consistent product day in, day out.

In the modern brewing tradition two families of yeast have been relied upon as the predominant choice for brewers—Saccharomyces Cerevisiae, a top fermenting ale yeast, and Saccharomyces Pastorianus, a bottom fermenting, cool temperature lager yeast. Within each of these families lay numerous separate branches or strains of yeast that produce a variety of beers. In the early part of the 20th century, ale yeast strains were used throughout the United Kingdom and Belgium, providing a slew of flavours and aromas from mild fruity esters, to pepper phenols, some creating crisp dry beers, others allowing a fuller body and pronounced maltiness. The isolation of lager yeast led to the development of the crisp, pale and refreshing beer. It soon gained tremendous traction rising to become the most consumed style of beer across the globe.

Yeast provides the alchemy required to create beer. A complex series of biochemical reactions occur over the course of days or weeks, where yeast consumes the fermentable sugars present in wort producing numerous by-products, such as alcohol and carbon dioxide. Adding yeast to wort does not necessarily mean a quality beer will be produced. It is up to the brewery staff to ensure that there is a sufficient amount of yeast present and that it is in good health. As yeast ferments, temperatures in the vessel must be regulated in order to ensure there are no undesired off flavours are created during the fermentation process.

Once fermentation is complete, the newly finished beer spends some time conditioning, which allows the flavours to even out leaving a refined and delicious beverage. From here, beer is packaged and makes its way out to thirsty beer drinkers and local establishments, ready to pour you a glass.

Bryan CarverThe Brew
Bryan Carver

Professional Brewer, Certified Cicerone® and Lover of All Things Beer. Joined The Buzz team in April 2018