title: Guaiacol and 4-methylphenol as specific markers of torrefied malts. Fate of volatile phenols in special beers through aging.
abstract: Phenol-specific extracts of 12 Belgian special beers were analyzed by gas chromatography hyphenated to olfactometry (AEDA procedure) and mass spectrometry (single ion monitoring mode). As guaiacol and 4-methylphenol were revealed to be more concentrated in brown beers (>3.5 and >1.1 μg/L, respectively), they are proposed as specific markers of the utilization of dark malts. Analysis of five differently colored malts (5, 50, 500, 900, and 1500 °EBC) allowed confirmation of high levels of guaiacol (>180 μg/L; values given in wort, for 100% specialty malt) and 4-methylphenol (>7 μg/L) for chocolate and black malts only (versus respectively <3 μg/L and undetected in all other worts). Monitoring of beer aging highlighted major differences between phenols. Guaiacol and 4-methylphenol appeared even more concentrated in dark beers after 14 months of aging, reaching levels not far from their sensory thresholds. 4-Vinylphenols and 4-ethylphenols, on the contrary, proved to be gradually degraded in POF(+)-yeast-derived beers. Vanillin exhibited an interesting pattern: in beers initially containing <25 μg/L, the vanillin concentration increased over a 14 month aging period to levels exceeding its sensory threshold (up to 160 μg/L). Beers initially showing an above-threshold level of vanillin displayed a decrease during aging.
authors.affiliation: Unité de Brasserie et des Industries Alimentaires, Earth and Life Institute (ELIM), Université catholique de Louvain , Croix du Sud 2, Box L7.05.07, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Scholtes
authors.forename: Sabrina
authors.initials: S
authors.lastname: Nizet
authors.forename: Sonia
authors.initials: S
authors.lastname: Collin
mesh_terms: D001515:Beer / Q000032:analysis*; D015415:Biomarkers / Q000737:chemistry; D003408:Cresols / Q000737:chemistry*; D002523:Edible Grain / Q000737:chemistry*; D005285:Fermentation; D005511:Food Handling; D008401:Gas Chromatography-Mass Spectrometry; D006139:Guaiacol / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D014835:Volatilization
chemical_list: D015415:Biomarkers; D003408:Cresols; D010636:Phenols; C032538:4-cresol; D006139:Guaiacol
keywords: beer aging; brown beers; phenols; special malts