What is Biotransformation?
Biotransformation refers to the transformation of compounds present in unfermented wort into altered, or altogether new compounds, through the metabolism of brewer’s yeast. Fermentation itself is a form of biotransformation whereby the yeast converts sugar into alcohol and CO₂.
Brewer’s yeasts are complex metabolic powerhouses which have adapted to produce a wide range of metabolites from a wide range of substrates. A number of these metabolites contribute to the characteristic sensory profile of both historic and modern beer styles. For example, yeast will metabolize malt sugars and precursors to produce fusel alcohols, esters, phenolic compounds, and organic acids as part of normal metabolism.
Yeast Interaction with Hops
Usually when brewers use the term biotransformation, they are referring specifically to hop biotransformation – the ability of yeast to interact with and modify flavor compounds derived from hops. When active yeast interacts with hops in the fermenter, it can increase aroma by releasing highly sensory active compounds from sensory inactive precursors, or change the flavor characteristics by modifying specific hop-derived flavor compounds.
Most of the discussion around biotransformation has focused specifically on terpenes, and polyfunctional thiols, both of which can contribute floral, fruity, and tropical flavours and aromas that form an important part of the flavor profile of many modern IPA styles. Other flavor compounds such as lactones and hop-derived esters may also play a supporting role in biotransformation sensory attributes.
Optimizing Biotransformation
Biotransformation can have a real impact on the flavor of the finished beer. The goal of this Biotransformation Resource Center is to help brewers to understanding the mechanisms involved in biotransformation to achieve specific flavor outcomes. Optimal biotransformation is achieved through careful consideration of yeast strain, hop variety, and brewing process.
Discover how different yeast strains interact with terpenes, thiols, and other flavor compounds, and how you can optimize your brewing process to increase biotransformation. You will also find information about our current biotransformation research projects and other technical resources.