Extraction et Analyse de polyphénols de marcs de raisin

Abstract : After a preliminary study that leads to the production of a first panel of the adhesive particles made primarily of grape tannins, UNGDA and LERMAB decided to continue their collaboration to further optimize the extraction process, in order to increase the value of marks on an industrial scale. Different extraction conditions were tested. It was demonstrated that a substitution of Na2CO3 by NaOH is possible, and allows significant savings at the industry level. The addition of urea seems to have a negative effect on the reactivity of the extracts (high gel time). Results of Ultraviolet Spectrophotometry (UV) confirmed the correlation between the gel time observed (and thus the reactivity of the extracts) and the rate of polyphenols determined by UV assay. The 13C NMR spectrum of a fraction of lyophilized tannins, dissolved in deuterium oxide (D2O), showed characteristics consistent with those of procyanidin units. A method of analysis by size-exclusion chromatography was developed, using THF as eluent, and using standards. The dimer fraction was found to be the more important. In presence of carbonates, the concentration of monomers is greater than in presence of sodium hydroxide.
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Master thesis
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Youcef Kireche. Extraction et Analyse de polyphénols de marcs de raisin. Sciences de l'environnement. 2012. ⟨hal-01869754⟩

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