Bitterness in alcoholic beverages: The profiles of perception, constituents, and contributors

Bitterness is a basic flavor in alcoholic beverages (beer, wine, liquor, and rice wine) and has physiological significance, although excessive and disharmonious bitterness is unpleasant. Current research on flavor in alcoholic beverages is primarily focused on volatile constituents and distinctive flavor compounds. However, studies on the recognition, identification, and metabolic mechanism of bitter substances are still in the preliminary phase. This review provides an integrated account of the signal transduction and recognition, composition and sensory properties of bitterness in alcoholic beverages. Abiotic and biotic factors within fermentation systems that may influence the bitterness of the fermented beverages are summarized. Future research on the molecular characteristics, taste attributes, and metabolic pathways of bitterness are discussed herein. Polyphenol and iso-α-acid extracted from grapes and hops are the typical bitter substances in wine and beer. Microbial metabolites, including bitter peptides and higher alcohols, are the primary contributors to bitterness in liquor and rice wine. These compounds can activate one or more specific bitter taste receptors. Manufacturing processes and sensory interactions also influence the perception of bitterness. Establishing normative bitterness scoring methods and distinguishing acceptable and unacceptable bitterness based on sensory physiology will continue to be the goals of bitterness research. Further elucidation of the metabolic mechanism underlying bitterness through a combination of omics and synthetic microbiology will allow for taste characteristics of alcoholic beverages to be manipulated.