Les thiols polyfonctionnels de la bière : première mise en évidence d'adduits S-conjugués à la cystéine dans le houblon
(2012)
Files
DocThèseJacquesGros.pdf
Closed Access - Adobe PDF
- 13.7 MB
Details
- Authors
- Supervisors
- Collin, Sonia
- Abstract
- (en) Polyfunctional thiols are very odorant volatiles involved in many food matrix aroma aroma such as coffee, wine and beer. The use of hops in brewery reveals far more complex than has been thought, especially when new exotic and citrusy varieties called "dual" are used. By conducting a specific extraction with pHMB followed by GC-PFPD analysis, we were able to quantify 41 sulfanyl compounds throughout 5 hop varieties. A specific profile emerges for every cultivar (e.g. 3S2EPral, 3Shptal, and 3SOal in Tomahawk; 3S4MPol, 4S4M2Pone, and 3SOal in the Nelson Sauvin; 3Shol, and 3SHptol in Cascade). Saaz variety exhibits the poorest polyfunctional thiol profile. Analysis of pilote brewing products confirmed that these compounds are transferred from hops to the wort. However, the polyfunctional thiol profile of beer clearly differs from this of hop. 3SOol and 3SHptol constitute key odorant compounds of Tomahawk hopped beer. In beers hopped with Cascade variety, intense grapefruit aromas are imparted by 3SHol and 3SHptol. During fermentation, the generation of many thiols carrying a 3 carbon atoms distance between HS and oxygen function prompted us to search for cysteinyl adducts in hops. RP-HPLC-HRMS/MS analysis allowed us to identify for the first time the S-3-(1-hydroxyhexyl)-cysteine conjugate in the Cascade variéty. Hops ethanolic extracts were purified on cation exchange column and then treated with the apotryptophanase enzyme (beta-lyase activity). Six adducts were found, three of them have never been described in other matrices. The occurence of the adduct of the very odorant MBT in hop pellets leads to reconsider the origin of this molecule in beer. Increasing intensities of 20 olfactory polyfunctional thiols were measured after bottle refermentation. 4S4M2Pone and 3SHol exceed their odour threshold. By standard addition, we confirmed the hydrolysis of S-3-(1-hydroxyhexyl)-cysteine during bottle refermentation.
- Affiliations
Citations
Gros, J. (2012). Les thiols polyfonctionnels de la bière : première mise en évidence d’adduits S-conjugués à la cystéine dans le houblon. https://hdl.handle.net/2078.5/46226