Cerevisia最新文献

Hydrophobins are exceptional proteins produced by fungi. Research over the last decade has led to a better understanding of their role in spontaneous self-assembly at hydrophobic/hydrophilic interfaces. This has resulted in many proposals for using hydrophobins in many important scientific and technological applications. Hydrophobins may become attractive as special biosurfactants, as foaming agents and for protein immobilization in the food industries and in biosensors. Moreover, they can be interesting as stabilizers for flavors, and as, encapsulating agents of trace ingredients in beverages. The use of hydrophobins in pharmaceutical formulations and in medicine is another interesting application as they cause an increased stabilization of drugs. The study of hydrophobins must also lead to a better understanding of the gushing phenomenon in beverages like beers, wines and ciders, which causes great economic losses in those fields. To recognize the positive and the negative aspects of hydrophobins these proteins should be commercially available at large scale which however is not the case. An overview of existing possibilities for applications may help to understand their behavior in different environmental conditions and to stimulate finding improved methods for isolation and purification, and possibly other unexpected applications.

Le suivi de tanks de garde d’une production industrielle montre que les arômes du houblon se solubilisent dans la bière dès les deux premières semaines du processus de houblonnage à cru (cas du linalool, du myrcène et de l’acide 3-méthylbutanoïque). Par contre, trois semaines sont nécessaires pour la production de molécules odorantes issues de glycosides du houblon (4-vinylsyringol, citronellol, béta-damascénone). De nombreux arômes soufrés (thiols polyfonctionnels) aux odeurs de fruits exotiques sont également libérés. Le procédé de houblonnage à cru se révèle donc bien plus complexe qu’une simple solubilisation des huiles essentielles du houblon, surtout si la période de maturation est prolongée.

Although hops are only added in relatively small amounts at particular stages of the brewing process, they have a high impact on the final beer flavor characteristics. The aroma of raw hops, caused by flavor-active constituents present in hop essential oil, clearly differs from the characteristic hoppy aroma of finished beer. Because of the very complex chemical composition of hop essential oil itself and insufficient knowledge on the many (bio)chemical conversions of hop oil components during the brewing process, the chemical background of hoppy aroma is still ill-defined. Since no reviews about the influence of yeast on hop oil-derived aroma compounds during the fermentation process – and thus the influence of fermentation on the hoppy aroma of final beer- have been spotted, this article was drawn up aiming at a clear overview of scientific research that has already been done in this field and of the current know-how, resulting thereof. Proposed flavor-active constituents for hoppy aroma (terpenes, sulfur compounds and oxygenated compounds) originating from hop essential oil and possible transformations of these compounds during fermentation will be discussed. In addition, the effect of yeast enzymes on hop glycosides will be reviewed, since several investigations point to their high potential as precursors of highly flavor-active aroma compounds that may contribute to the hoppy aroma of beer.