Assessment of colour and tannin extraction in Tempranillo and Cabernet-Sauvignon using small-scale fermentation vessels

Researchers typically perform winemaking experiments using small volumes of grapes. This study examined which small-vessel volume (10, 25, 50 and 100 L) gives better repeatability during red winemaking extraction of colour and tannin in research studies. Few studies have actually evaluated the repeatability of small-scale fermentations using two varieties of different phenolic potential: Tempranillo and Cabernet-Sauvignon. We investigated how volume size may affect the composition of colour and tannins for these two varieties and result in potentially different phenolic contents. Furthermore, for each variety, we compared the small scale vessel with a commercial fermentation using a 2.500 L capacity. 50 L tanks resulted in optimum extraction of phenols and colour. High repeatability was observed for alcohol content, pH and total acidity, anthocyanins, and procyanidins for both varieties amongst vessel sizes. Kinetics of fermentation performed faster in big berry driven grapes (Tempranillo) regardless of the volume. Instead, for small berry grapes (Cabernet-Sauvignon), vessel size affected the kinetics or fermentation and therefore the extraction can be altered. Very high repeatability for the alcohol by volume, pH and total acidity (CV ≤ 7 %) as well as anthocyanins and procyanidins by HPLC (15 % ≤ CV ≤ 20 %) for both varieties in all volume sizes. This research provides a solid basis for validating the reproducibility of small-scale fermentations of two red grapevines with different phenolic potential and sheds new light on the potential and limitations of small-scale winemaking.