Volatile phenols: Emergence of specific profiles among Belgian specialty beers

Sensory Session
Caroline Scholtes, Université catholique de Louvain, Earth and Life Institute (ELIM), Louvain-la-Neuve, Belgium
Co-author(s): Masatatsu Shiba, Asahi Breweries Ltd., Ibaraki, Japan; Thomas Haube, Sabrina Nizet, and Sonia Collin, Université Catholique de Louvain, Earth and Life Institute (ELIM), Louvain-la-Neuve, Belgium

ABSTRACT: Volatile phenols are responsible for spicy notes in a large range of beverages. Various flavor active phenolic compounds have been detected in beer. Among them, 4-vinylguaiacol and 4-vinylphenol are well known to release clove-like flavor in Belgian white beers made with unmalted wheat. In many other top fermented blond, amber, and brown beers, phenols also determine the overall flavor perception. In the present work, phenol-specific extracts of 14 Belgian special beers were investigated by gas chromatography-olfactometry (GC-O/AEDA methodology) and gas chromatography-mass spectrometry (GC-MS). Different profiles were highlighted according to the raw materials used (special malt, organic malt, wheat), yeast strain, or maturation vessel. 4-Vinylphenol, 4-vinylguaiacol, and vanillin were found well above their respective thresholds in beers produced with highly Pof+ yeast. On the other hand, a low ethyl/vinyl ratio was found in brands where Brettanomyces strains are used for secondary fermentation, bottle refermentation, or cask maturation. Finally, two original phenols emerged as interesting markers, allowing us to authenticate the use of torrefied/chocolate malts.

Graduating in 2007 as a bio-engineer from Catholic University of Louvain (Belgium), Caroline Scholtes completed her education in 2008 with a master’s degree in brewing science. In 2010, she started a Ph.D. program at the same university. Her research focuses on aging of Belgian special beers with regard to raw materials, brewing process, and storage conditions and correlates this to modification of organoleptic profile, especially Madeira off-flavor and volatile phenols. She is also a teaching assistant in beer chemistry at the same university.