Wine lees valorization: antioxidant activities


Wine lees are the dregs formed during the different fermentation steps in the vinification process.  These wine less constitute a novel source rich in polyphenols and other compound of high added value. Freeze-dried aging wine lees were, for the first time, exhaustively characterized in terms of antioxidant capacity with different assays: ORAC, HORAC, HOSC and FRAP. In order to develop this characterization, several solid-liquid extractions (5 min of stirring and 10 min of sonication) were performed with six different solvents. Furthermore, the terpene and sugar contents of the wine lees were analyzed.

The total polyphenol content (TPC) was measured using the Folin Ciocalteu reagent. The results showed in Figure 1 proved that the polyphenol contents depend strongly on the solvent used varying from 40 to 254 mgGAE/g. Also the flavonoid content (FLV) presents the same behavior as the TPC.

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Figure 1: Results of TPC (mgGAE/g) and FLV (mgCAT/g) for the different solvents extractions

According to these results the most promoting solvent for polyphenol extraction is a mixture of EtOH:H2O (75:25) (v/v).

The antioxidant activity results for the different activities assays are collected in the Figure 2.

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Figure 2: Results of ORAC (ÎĽmol TE/L), HORAC (ÎĽmol CAE/L), HOSC (ÎĽmol TE/L) and FRAP (ÎĽmol TE/L) for the different solvents extractions.

In these figure it can be seen the relationships between the different six extracts and the different antioxidant assays. EtOH:H2O (75:25) (v/v) mixture presents the best values for HORAC and HOSC activities, meanwhile those extracts obtained with MeOH are the most promising for the ORAC and FRAP assays.

In addition, other compounds were analyzed from wine lees.  Terpenes were studied applying a thin-layer chromatography (TLC) with the Liebermann-Burchard reagent was performed, but after all, it was possible to disclose that no terpenes were present in the wine lees. Some sugars were detected in the water-extracted fraction of wine lees; glucose is the most abundant sugar present in these wine lees (1740 ppm) but, also, there is a significant concentration of MGX which means Mannose, Gallactose or Xilose (297 ppm).

On the ongoing work, an statistical study it is been doing in order to correlate the contribution of the compounds analyzed with HPLC from the different extracts, with the different antioxidant activities.

Rut Romero – Project WineSense

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