South Africa Wine Research Projects 2026

3. OENOLOGY RESEARCH NEW PROJECT

3.1 WINE IMPROVEMENT

JUICE OBTAINED FROM GRAPE LEES: EFFECTS ON WINE COMPOSITION

SAGWRI WdT 26-01 Prof Wessel du Toit, South African Grape and Wine Research Institute, Stellenbosch University Start date: 2026

AIM AND INDUSTRY RELEVANCE: White and rosé winemaking generates grape lees that still contain juice, which are often discarded or used inconsistently by wineries. Although some producers extract this remaining juice and add it to the final fermentation, the chemical and sensory contributions of this lees-derived juice remain poorly understood. Feedback from winemakers suggests it may enhance mouthfeel and specific aroma characteristics, yet the scientific literature provides limited insight into its actual impact. The project aims to investigate how juice obtained from grape lees affects the chemical composition and sensory profile of white and rosé wines. This research project aims to provide the wine industry with evidence-based guidance on an underexplored winemaking practice. By understanding the potential value of lees-derived juice, producers may identify a cost-effective method to enhance the aroma and flavour complexity of neutral juices. The findings could help wineries optimise juice recovery, reduce waste, and create more differentiated and higher-value products. The objectives of this project are:

• To determine the effect of juice from grape lees on wine composition, • To determine the effect of grape lees scraping on wine composition.

40

SOUTH AFRICA WINE RESEARCH 2026