Original research articles

A S-cysteine conjugate, precursor of aroma of White Sauvignon

Abstract

4-mercapto-4-methylpentan-2-one (4-MMP), a strongly odorant compound responsible for the « boxtree » or « broom plant » odour of the Sauvignon wines, can be enzymaticaly released in vitro from an odourless must extract. The enzyme source used is a cell-free extract of the gastrointestinal bacterium Eubacterium limosum. This crude preparation exhibits a cysteine β-lyase activity which requires the presence of pyridoxal phosphate. The release of 4-MMP is inhibited when the substrate is previously treated with N-hydroxysuccimide acetate which reacts with a primary amine. The same bacterial extract is also able to release 4-MMP, pyruvic acid and ammonium, from S-(4-méthylpentan-2-one)-L-cysteine. On the other hand, the cleavage of S-(4-méthylpentan-2-one)D,L-homocysteine and S-(4-méthylpentan-2-one)- glutathione is very limited. These results suggest that the precursor of 4-MMP in Sauvignon must is a S-cysteine conjugate. Such an aroma precursor in grapes or in other fruits has never been round berore.

Authors


Takatoshi Tominaga

Affiliation : Faculté d'oenologie de Bordeaux, I.S.V.V., UMR OEnologie, 351 cours de la Libération, 33405 Talence cedex, France


Isabelle Masneuf-Pomarède

Affiliation : Université de Bordeaux, Unité de Recherche Œnologie EA 4577, USC 1366 INRA, ISVV, F-33140 Villenave d’Ornon, France; Bordeaux Sciences Agro, F-33175 Gradignan, France

I-masneuf@enitab.fr

Denis Dubourdieu

Affiliation : Faculté d’oenologie, UMR 1219 OEnologie, Université de Bordeaux, ISVV, 210, chemin de Leysotte, CS 50008, 33882 Villenave d'Ornon, France

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