Jean-Paul Lepoutre

Wine flavor enhancement through the use of exogenous fungal glycosidases

Abstract The use of a pectinase enzyme preparation in winemaking containing relevant glycosidase activities for the hydrolysis of glycosidically bound aroma compounds allowed to increase the levels of volatiles, monoterpenes, C 13 -norisoprenoids, and benzene derivatives. The highest increase was for the wine obtained from the juice enriched by glycosides through the contact of juice with skin parts of grape berry. Enzyme treatment enhanced the attributes, honey, lime, and smoky. The enzyme-treated wines were highly significantly different from the control wines and preferred to control wines.

Enzymic production of oligosaccharides from corncob xylan

Abstract An endo-1,4-β-xylanase (E.C.3.2.1.8) fraction of high specific activity was isolated from a 180-l culture supernatant of Clostridium thermolacticum and partially purified by a one-step ion-exchange chromatography. This xylanase fraction, which contained 290 U mg −1 of protein, was used for the large-scale deploymerization of a xylan extracted from corncob meal. The oligosaccharides produced were absorbed on charcoal and eluted stepwise with ethanol to yield mainly xylobiose, xylotriose, and arabino-xylo-oligosaccharides .

Determination of trifluoroacetylated glycosides by gas chromatography coupled to methane negative chemical ionization mass spectrometry

Abstract Gas chromatography coupled to methane chemical ionization mass spectrometry was used for qualitative determination of trifluoroacetylated plant glycosides. The mass spectra obtained exhibited characteristic fragment ions of the sugar moiety and molecular or pseudo-molecular ions. The pattern of these chemical ionization spectra was influenced by source temperature. This method was applied to the structural determination of glycosides from purple passion fruit and muscat wine (Muscat of Frontignan) extracts obtained by adsorption on Amberlite XAD-2.

Biotransformation of C13-norisoprenoids and monoterpenes by a cell suspension culture of cv. Gamay (Vitis vinifera)

A cell suspension culture of cv. Gamay was studied for its ability to metabolize two different C13-norisoprenoidic volatiles, β-ionone and dehydrovomifoliol, together with monoterpenes, geraniol and linalool, biogenetically common pathways sharing compounds. β-Ionone was totally metabolized leading to fourteen norisoprenoidic volatiles oxygenated mainly at carbons 3 or 4 of the cyclohexane ring or reduced at side chain. The biotransformation of dehydrovomifoliol was at a lesser extent, giving rise to oxygenated and reduced derivatives. The norisoprenoidic metabolites were present both under free and glycosylated forms. Geraniol and linalool were also metabolized, leading to several free and glycosylated compounds.