Pre-fermentative addition of an enzymatic grape seed hydrolysate in warm climate winemaking. Effect on the differential colorimetry, copigmentation and polyphenolic profiles

• Seeds enzymatic hydrolyzate improves colour quality of warm-climate red wines.
• Wines show better pigments and copigments characteristics during stabilization.
• Lower loss of colour is observed in treated wines, without changes on tonality.
• High quantity of enzymatic hydrolyzate is detrimental to the colour of red wines.
• Colour changes provoked by high quantity of hydrolyzate are visually perceptible.

The effect of adding an enzymatic hydrolysate of grape seeds (EH-GS) during Syrah wine fermentation in a warm climate has been evaluated. We focused on the polyphenolic composition as well as the application of differential and tristimulus colorimetry to colour data. This is the first attempt at using this oenological alternative to avoid common colour losses of red wines elaborated in a warm climate. The addition of 250 g (simple dose, SW) of EH-GS to 120 kg of fermentation material promoted a significant (p < 0.05) increase in the polyphenolic content of stored wines, especially in benzoic acid, hydroxycinnamic acid derivative, flavonol and anthocyanin levels. This increase could promote a higher copigmentation percentage and maximum colour stabilization (C∗ab) without significantly changing the wine tonality. Unexpectedly, the use of a double quantity (DW) of EH-GS resulted in significantly less chroma than for control wines (CW), demonstrating visually perceptible colour changes (ΔE∗ab > 3 CIELAB units).