Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Microbiology, aroma, beer, yeast, hops, molecular biology, malt, HOP HUMULUS-LUPULUS, SAKE YEAST MUTANTS, BETA-PHENYLETHYL-ALCOHOL, ACETATE ESTER PRODUCTION, AMINO-ACID BIOSYNTHESIS, UNSATURATED FATTY-ACIDS, VOLATILE THIOL RELEASE, ODOR-ACTIVE COMPOUNDS, SACCHAROMYCES-CEREVISIAE, ISOAMYL ACETATE, Alcoholic Beverages, Beer, Food Microbiology, Humulus, Odorants, Proteins, Saccharomyces cerevisiae, Volatile Organic Compounds, 0605 Microbiology, 1108 Medical Microbiology, 3107 Microbiology

Abstract:

Aroma compounds provide attractiveness and variety to alcoholic beverages. We discuss the molecular biology of a major subset of beer aroma volatiles, fruity and floral compounds, originating from raw materials (malt and hops), or formed by yeast during fermentation. We introduce aroma perception, describe the most aroma-active, fruity and floral compounds in fruits and their presence and origin in beer. They are classified into categories based on their functional groups and biosynthesis pathways: (1) higher alcohols and esters, (2) polyfunctional thiols, (3) lactones and furanones, and (4) terpenoids. Yeast and hops are the main sources of fruity and flowery aroma compounds in beer. For yeast, the focus is on higher alcohols and esters, and particularly the complex regulation of the alcohol acetyl transferase ATF1 gene. We discuss the release of polyfunctional thiols and monoterpenoids from cysteine- and glutathione-S-conjugated compounds and glucosides, respectively, the primary biological functions of the yeast enzymes involved, their mode of action and mechanisms of regulation that control aroma compound production. Furthermore, we discuss biochemistry and genetics of terpenoid production and formation of non-volatile precursors in Humulus lupulus (hops). Insight in these pathways provides a toolbox for creating innovative products with a diversity of pleasant aromas.