Sabrina Nizet

Occurence of odorant polyfunctional thiols in the super alpha Tomahawk hop cultivar. Comparison with the thiol-rich Nelson Sauvin bitter variety

Tomahawk hop (Humulus lupulus) is a recently developed Super Alpha cultivar (14-18% α-acids w/w), already widely used by brewers to impart bitterness and a citrus-like aroma to beer. By comparison with two bitter varieties (Nelson Sauvin and Nugget) and two aromatic ones (Cascade and Saaz), the Tomahawk cultivar showed a very particular terpenoid profile, rich in both α- and β-selinenes (>600 mg/kg IST equiv in total), methyl geranate (>40 mg/kg IST equiv), and geraniol (>200 mg/kg). Tomahawk also proved to contain a wide variety of odorant polyfunctional thiols. The major β-sulfanyl acetate, 3-sulfanyl-2-ethylpropyl acetate, newly identified here, was found at similar levels in the famous Sauvignon-like Nelson Sauvin and Tomahawk varieties (15-44 μg/kg IST equiv). On the other hand, lower levels of total β-sulfanyl alcohols were measured in Tomahawk, although 3-sulfanylhexan-1-ol was found at a similar level and the 3-sulfanyl-4-methylpentan-1-ol previously claimed to be specific to the Nelson Sauvin variety was also evidenced in the Super Alpha cultivar (9-13 μg/kg IST equiv). As revealed by boiling and fermentation, Tomahawk hop also contains very interesting bound polyfunctional thiols that should be investigated for better use by brewers.

Quantitation of Selected Terpenoids and Mercaptans in the Dual-Purpose Hop Varieties Amarillo, Citra, Hallertau Blanc, Mosaic, and Sorachi Ace

Free terpenoids and both free and bound polyfunctional thiols were investigated in five selected dual-purpose hop cultivars. Surprisingly, the dual-purpose Sorachi Ace variety was found to contain higher amounts of farnesene (2101 mg/kg) than aromatic hops such as Saaz but only traces of 3-methylbutylisobutyrate, a compound that usually distinguishes all bitter varieties. All five cultivars investigated here showed an exceptional citrus-like potential explained by either monoterpenic alcohols or polyfunctional thiols. Among the monoterpenic alcohols, β-citronellol at concentrations above 7 mg/kg distinguished Amarillo, Citra, Hallertau Blanc, Mosaic, and Sorachi Ace from Nelson Sauvin and Tomahawk, two previously investigated dual-purpose hops, while linalool (312 mg/kg) and geraniol (211 mg/kg) remained good discriminating compounds for Nelson Sauvin and Tomahawk, respectively. Regarding polyfunctional thiols, higher amounts of 3-sulfanylhexyl acetate (27 μg/kg) characterized the Citra variety. Free 4-sulfanyl-4-methylpentan-2-one proved discriminant for Sorachi Ace, while the bound form is predominant in Nelson Sauvin. On the other hand, an S-conjugate of 3-sulfanylhexan-1-ol was found in Sorachi Ace at levels not far from those previously reported for Cascade, although the free form was undetected here. Both free and bound grapefruit-like 3-sulfanyl-4-methylpentan-1-ol (never evidenced before the present work) emerged as discriminating compounds for the Hallertau Blanc variety. The apotryptophanase assay also allowed us to evidence for the first time an S-conjugate of 2-sulfanylethan-1-ol.

Stilbenic Profile of Cocoa Liquors from Different Origins Determined by RP-HPLC-APCI(+)-MS/MS. Detection of a New Resveratrol Hexoside

trans-Resveratrol and trans-piceid were recently discovered in chocolate. In the present work, both were quantified by RP-HPLC-APCI(+)-MS/MS in 22 cocoa liquors from 11 different countries. A very large range of concentrations was observed for trans-piceid. The most concentrated sample (Arriba 06) reached 0.4 and 2.6 mg/kg of trans-resveratrol and trans-piceid, respectively, but in other cultivars stilbene levels were five times lower. Neither cis-resveratrol nor cis-piceid was found in cocoa liquors. An unknown compound eluting 0.5 min before trans-piceid and present at concentrations up to 0.8 mg/kg of trans-piceid equivalents in cocoa liquors was tentatively identified by HRMS as a trans-piceid-like hexoside.

Guaiacol and 4‑Methylphenol as Specific Markers of Torrefied Malts.Fate of Volatile Phenols in Special Beers through Aging

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.

Occurrence of Theaspirane and its Odorant Degradation Products in Hop and Beer

In model oxidized media, six theaspirane-derived compounds were identified by gas chromatography-high resolution mass spectrometry: 4-hydroxy-7,8-dihydro-β-ionone, 6-hydroxy-7,8-dihydro-α-ionone, dihydrodehydro-β-ionone, two monoepoxides, and a derived alcohol. Only 4-hydroxy-7,8-dihydro-β-ionone and dihydrodehydro-β-ionone have been described previously in the literature. Investigation of hop revealed five of these compounds in free form together with theaspirane (especially in the Mosaic variety), while the Citra and Amarillo hop varieties emerged as very interesting for the release of theaspirane, 4-hydroxy-7,8-dihydro-β-ionone, and dihydrodehydro-β-ionone from glucoside precursors. For the first time, theaspirane, 4-hydroxy-7,8-dihydro-β-ionone, 6-hydroxy-7,8-dihydro-α-ionone, and both monoepoxides were found in a fresh commercial top fermentation beer (only theaspirane, 4-hydroxy-7,8-dihydro-β-ionone, and dihydrodehydro-β-ionone have recently been mentioned as Gueuze constituents).

Key odorants of Jura Flor-Sherry wines : strong analogy with Gueuze beers

The analogy of “yellow wine” flavors with some Gueuze beers led us to compare their aroma profiles. Two different extractions were applied on three wines and two beers. By using GC-olfactometry (the AEDA method) and GC-MS, four oxidation-derived odorants (sotolon, abhexon, dihydrodehydro-β-ionone, and 4-hydroxy-7,8-dihydro-β-ionone) were evidenced in both matrixes. Isovaleric acid, 4-ethylguaiacol, and several oak ageing-derived compounds were also evidenced in both matrixes.The analogy of “yellow wine” flavors with some Gueuze beers led us to compare their aroma profiles. Two different extractions were applied on three wines and two beers. By using GC-olfactometry (the AEDA method) and GC-MS, four oxidation-derived odorants (sotolon, abhexon, dihydrodehydro-β-ionone, and 4-hydroxy-7,8-dihydro-β-ionone) were evidenced in both matrixes. Isovaleric acid, 4-ethylguaiacol, and several oak ageing-derived compounds were also evidenced in both matrixes.

Chapter 62 – Key Odorants of Jura Flor-Sherry Wines: Strong Analogy with Gueuze Beers

The analogy of “yellow wine” flavors with some Gueuze beers led us to compare their aroma profiles. Two different extractions were applied on three wines and two beers. By using GC-olfactometry (the AEDA method) and GC-MS, four oxidation-derived odorants (sotolon, abhexon, dihydrodehydro-β-ionone, and 4-hydroxy-7,8-dihydro-β-ionone) were evidenced in both matrixes. Isovaleric acid, 4-ethylguaiacol, and several oak ageing-derived compounds were also evidenced in both matrixes.The analogy of “yellow wine” flavors with some Gueuze beers led us to compare their aroma profiles. Two different extractions were applied on three wines and two beers. By using GC-olfactometry (the AEDA method) and GC-MS, four oxidation-derived odorants (sotolon, abhexon, dihydrodehydro-β-ionone, and 4-hydroxy-7,8-dihydro-β-ionone) were evidenced in both matrixes. Isovaleric acid, 4-ethylguaiacol, and several oak ageing-derived compounds were also evidenced in both matrixes.

Odorant Polyfunctional Thiols Issued from Bottle Beer Refermentation

Bottle refermentation which imparts beer effervescence and resistance against infection and oxidation is also known to improve flavor profile and stability. By this process, some stale off-flavors exhaled by aldehydes (trans-2-nonenal, 3-methylthiopropionaldehyde, 3- methylbutanal ..) are reduced into alcohols (1, 2). Unfortunately, yeast esterases can also strongly affect the beer fruity character by hydrolyzing isoamyl acetate, ethyl hexanoate and ethyl octanoate (1, 2). Thiols are known to have a strong impact on the overall aroma of fermented beverages (3). More than ten polyfunctional thiols were detected in fresh lager beers (4). The thiols profile of refermented beer has been little studied. In this work, the polyfunctional thiol contents of commercial and pilot beers submitted or not to bottle refermentation were compared. A strong organoleptic impact of the bottle refermentation process was evidenced in all samples by a training panel (70%). A specific pHMB thiols extraction (5) was applied and the extracts analyzed by GC-MS, GC-PFPD and GColfactometry (AEDA). A large number of sulfanylalcools, sulfanylacetates and sulfanylcarbonyles revealed produced during the refermentation process, especially after three weeks. Among them, 3-sulfanylpropanol reached a FD olfactometric values up to 32768. According to their beta-sulfanyl structures, hop cystein adducts are suspected to be hydrolyzed by refermentation yeast-derived lyases. Therefore, a better control of the refermentation process requires both an excellent control of yeast vitality and a strict selection of the hop varieties.