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Study of the impact of oenological processes on the phenolic composition and biological activities of Lebanese wines

Ghanem, Chantal. Study of the impact of oenological processes on the phenolic composition and biological activities of Lebanese wines. PhD, Génie des Procédés et de l'Environnement, Institut National Polytechnique de Toulouse, 2017

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Abstract

The aim of this study was to determine the influence of different winemaking techniques on phenolic composition and biological activities of musts and wines from grapes of Syrah and Cabernet sauvignon from two distinct Lebanese regions (Bekaa valley and Chouf district) and two consecutive vintages (2014 and 2015). Among these processes the impacts of pre-fermentative cold and heating maceration, enzymatic treatment, two different commercial yeast strains and fining agents were discussed in our study. Spectrophotometric and HPLC analysis of phenolic compounds showed that the pre-fermentative heating maceration leads to a better extraction of phenolic compounds than the pre-fermentative cold maceration. Tannins and total polyphenols extraction are favored by the temperature and the prolongation of maceration. Extraction of anthocyanins is also favored by the temperature with short duration since the extension of the maceration leads to a degradation of these compounds. Maceration enzymes addition at early stage of maceration, promoted higher concentration of total polyphenol and antioxidant activity compared to those macerated without added enzymes. Alcoholic fermentation results in a decrease of total polyphenols content which revealed differences between wines derived from X and Y strains. After alcoholic fermentation, almost all of the wine samples presented an increase of their percentage of inhibition with the occurrence of new types of biological activities which doesn‟t existed at must level. At the end, the results showed the importance of selecting a fining agent according to the type of wine and to minimize the dose of fining applied in order to conserve the content of phenolic compounds in wine.

Item Type:PhD Thesis
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Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
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Research Director:
Taillandier, Patricia and El Rayess, Youssef
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Deposited On:31 May 2017 14:29

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