Higher alcohols and their derived acetyl esters are important flavour components in beer. They are by-products of amino acid metabolism in brewing yeast. Amino acids can either be taken up from the wort, or synthesized by the yeast itself. Yeast biosynthetic pathways leading to formation of the amino acids leucine, valine, isoleucine, methionine, and cysteine are important for beer flavour. Most of the genes encoding the enzymes involved in the synthesis of these amino acids have been identified and their regulation studied. Inactivation, mutation or over-expression of these genes may result in new yeast strains, producing beer with either higher or lower levels of certain aroma compounds. One example of a recent research project is the development of brewing yeasts with enhanced production of the flavor stabilizer, SO2.
