Beer Aroma Compounds: Key Odorants, Off-Flavour Compounds and Improvement Proposals

Beer aroma is a critical quality attribute shaped by volatile compounds from malt, hops, and yeast metabolism; however, the appearance of off-flavours can compromise it. This review identifies and describes the main aroma-active compounds that define the beer's sensory profile, emphasising both key odorants and undesirable notes, such as diacetyl, dimethyl sulphide, acetaldehyde, and light-struck thiols. Based on recent literature, a troubleshooting guide was developed to link specific odours with their particular chemical compounds, origin, and corrective actions. The findings highlight how the composition of raw materials, processing and storage conditions, treatments, fermentation management, and even packaging play an important role in flavour stability. By identifying the sources of common defects and offering practical solutions, this work provides brewers with strategies to enhance aroma control and improve overall beer quality.