Yeast

Brewers don’t do hard work.

That is not to say brewing is not a physically and mentally demanding job, but our task as brewers is to herd our microbes of choice – and let them do the hardest work in the brewery, munching on sugars to produce the alcohol in our beer. In the video above, Beerblefish owner, James Atherton, shows us how different microbes do this job (while the video is generally accurate, it’s fair to say it might not be entirely serious…)

Most brewers choose to use a single culture of Brewer’s Yeast, often from the Saccharomyces genus, while some making sours will use Lactobacillus and Saccharomyces together; people who are gluttons for punishment, like us at Beerblefish, will use a varied mix of yeasts (and occasionally blends of bacteria). As you can imagine, herding one invisible fungus can be challenging, herding up to five in a single brew requires a little more attention to detail, but that’s what gives our heritage beers their distinctive flavour and character.

Different yeasts produce different flavours, work at different rates and will consume different sugars/dextrins. Saccharomyces will usually start consuming simple glucose before turning their attention to other monosaccharides or longer chain sugars. Lactobacillus will rapidly multiply and chew through glucose, fructose, sucrose, lactose and galactose in that order – but they are not able to metabolise long chain dextrins or starches. Brettanomyces tend to work a little more slowly than brewing strains of Saccharomyces in an aerobic environment then, slow down considerably to about half the metabolic rate in an anaerobic environment.

An interesting thing, if you are herding your microbes, is that placing saccharomyces and lactobacillus in the same environment causes Saccharomyces strains to abandon their usual preferences for simple sugars for more complex sugars. The presence of Lactobacillus in a Saccharomyces culture causes them to rapidly metabolise all the sugars they can pull in. This can lead to more off flavours and is why many brewers these days will kettle sour with Lactobacillus rather than allowing it into primary fermentation.