Occurrence of Polyfunctional Thiols in Fresh Lager Beers

Abstract

Polyfunctional thiols are known to have a strong impact on the overall aroma of many fermented foods. Surprisingly, very little data is available on their occurrence in beer. A specific extraction with p-hydroxymercuribenzoic acid was performed on four different fresh light-protected lager beers. gas chromatography-olfactometry, gas chromatography-mass spectrometry, and gas chromatography-pulsed-flame photometer detector analyses of the extracts revealed the presence of more than 10 polyfunctional thiols. All of them were absent from wort, suggesting a key role of the H(2)S excreted by yeasts. 3-Methyl-2-buten-1-thiol, 2-mercapto-3-methylbutanol, 3-mercapto-3-methylbutanol seem to be created from hop allylic alcohols via four different mechanisms: nucleophilic substitution, addition-elimination, and radical anti-Markovnikov or electrophilic Markovnikov additions. 1,4 Addition of hydrogen sulfide to wort alpha,beta-unsaturated aldehydes or ketones may explain the synthesis of 1-mercapto-3-pentanol, 3-mercaptohexanol, and 4-mercapto-4-methyl-2-pentanone through fermentation. Finally, 2-mercaptoethanol, 3-mercaptopropanol, and their corresponding acetates may derive from Ehrlich degradation of sulfur amino acids, while 2-methyl-3-furanthiol should be logically issued from Maillard reactions.

Metabolomic profiling of beer reveals effect of temperature on non-volatile small molecules during short-term storage

“…Sulphur is often produced in stored beer due to Strecker degradation of methionine (Gijs, Chevance, Jerkovic, & Collin, 2002). The excess sulphur is a product of yeast fermentation and is typically found in volatile metabolites (Vermeulen, Lejeune, Tran, & Collin, 2006). The elevated quantities of 5-MTA in aged beer may be due to an interaction between purines and excess sulphur.…”

Engineering Saccharomyces cerevisiae To Release 3-Mercaptohexan-1-ol during Fermentation through Overexpression of an S. cerevisiae Gene, STR3 , for Improvement of Wine Aroma

“…They are found in a wide range of foods (39), including animal products such as yoghurt and cheese, fruits, vegetables, tea, coffee, and alcoholic beverages (2,4,33,35,38). Of particular interest in wine fermentation are the aromatic volatile thiols, 4-mercapto-4-methylpentan-2-one (4MMP), 3-mercaptohexan-1-ol (3MH), and 3-mercaptohexyl acetate.…”

Occurrence of the ribes odorant 3‐sulfanyl‐3‐methylbutyl formate in aged beers

“…In headspace gas chromatography of cat urine, 3-sulfanyl-3-methylbutan-1-ol and its formate have recently been identified as candidate felinine derivatives. [16] In a previous study dedicated to polyfunctional thiols in lager beers, [7] no sulfanyl formate was found. Only two sulfanyl acetates were found: 2-sulfanylethyl acetate and 3-sulfanylpropyl acetate, both characterized by empyreumatic descriptors.…”

“…[4] In beer, 2-sulfanyl-2-methyl-4-methoxybutane has never been detected. [7,8] It is even often used as an internal standard for beer thiol extraction. [9] With the aroma extract dilution analysis technique applied to an aged beer extract, Schieberle revealed the possible relevance of 3-sulfanyl-3-methylbutyl formate to the beer ribes note.…”