4 research outputs found
Formation of Flavanol-aldehyde Adducts in Barrel-aged White Wine - Possible Contribution of These Products to Colour
[EN] This paper describes the formation and diversity of new compounds resulting from the polymerisation of furanic and
phenolic flavanol-aldehydes with HPLC¿DAD and LC¿ES/MS analysis. Polymerisation, resulting from nucleophilic
reactions, formed dimers, trimers, soluble and insoluble polymers. Reactions in hydroalcoholic solution with pure
aldehydes (phenolic and furanic) and flavanols (catechin) were studied. The study was repeated with different
aldehydes in white wine. This research focused particularly on the colour properties of the released products and their
potential impact on the colour of white wine. Some products were purified and isolated; these were mainly catechinfurfuraldehyde,
catechin-methyl-5-furfuraldehyde, catechin-hydroxymethyl-furfuraldehyde, catechin-vanillin, and
catechin-syringaldehyde dimers. The most powerful coloured products resulted from furanic aldehydes. Over the
course of the experiment, the reaction produced dimers, trimers and oligomers. After 50 to 60 days, the colour of the
solution was mainly due to soluble polymeric forms. In addition, the role of SO2
, generally used during vinification
and ageing, was studied. The influence of SO2 on the kinetics of the reaction was limited.Vivas, N.; Nonier, MFB.; Absalon, C.; Lizama Abad, V.; Jamet, F.; De Gaulejac, NV.; Vitry, C.... (2008). Formation of Flavanol-aldehyde Adducts in Barrel-aged White Wine - Possible Contribution of These Products to Colour. South African journal of enology and viticulture. 29(2):98-108. http://hdl.handle.net/10251/105310S9810829
Occurrence and specificity of glucose oxidase (E.C: 1.1.3.4) in botrytized sweet white wine. Comparison with laccase (E.C: 1.10.3.2), considered as the main responsible factor for oxidation in this type of wine
Two types of oxidizing enzymes are present in botrytized white grapes and wines: laccase (PPO) and glucose oxidase (GOX). The evolution of these two enzymes is similar both during the over-ripening of grapes and during wine making. Yet, PPO is severely inhibited by the addition of SO2 following the alcoholic fermentation, and shows a marked instability in both the must and wine environments. GOX, however, remains free and active in solution and helps develop the main characteristics of the wine. In particular, as is to be expected from its activity, GOX oxidizes tartaric acid, ethanol and glycerol, the major components of must and wine, respectively to glyoxylic acid, acetaldehyde and glyceraldehyde. And then, by nucleophilic additions under acidic conditions, these products react with catechins and proanthocyanidins to form several new compounds, some of which appear in a colored form. These reactions can have an impact on the visual quality of the wine.