Yeast – the black swan of brewing

"Yeasts are still living organisms and requires some TLC to perform optimally"

You might be asking yourself that if beer was brewed according to the Reinheitsgebot since 1516 until 1993, why is it even important to include yeast in this order? Although the amount (in terms of mass) of yeast required is the least of all the other ingredients of the ingredients listed, yeast defines the character and flavour of the final product.

During fermentation yeast consume sugars to produce energy in a metabolic pathway know as glycolysis, which culminates in the formation of ethanol, CO2 and various esters, phenols, and higher alcohols. Alcohol production is often top priority during fermentation; however, yeasts are still living organisms and requires some tender loving care (TLC) to perform optimally. If the fermentation is stressed, the yeast can produce various metabolic intermediates which have flavours and aromas ranging from medicinal to metallic and smoke. Besides being out of style, these flavours can ruin a perfectly brewed beer irrespective of the quality of the other ingredients.

Therefore, besides being essential for converting the sugars in beer, wine or other fermented products to ethanol, yeast also play a significant role in the quality of the final product. Considering the history of yeast in early brewing, this simple organism truly is the black swan of brewing.

Author: Dr.?Stefan Hayward