WINETECH Technical Yearbook 2021

OENOLOGY RESEARCH | JUNE 2021

Grape seed powder to improve heat stability in Sauvignon blanc wines – effectiveness and sensory impact

CARIEN COETZEE: Basic Wine, Stellenbosch KEYWORDS: Grape seed powder, heat stability, fining.

GRAPE SEEDS ARE NATURAL BY-PROD- UCTS of winemaking and are usually dis- carded after the separation of the solids from the juice. However, in a quest to find an effective bentonite replacement that is sustainable and environmentally friendly, researchers have turned to winery waste for possible solutions. INTRODUCTION The use of powdered grape seeds as an alternative to bentonite for the removal of haze-forming proteins have been demonstrated in small-scale preliminary studies (Romanini et al ., 2020). Results from these laboratory-scale tests showed that the addition of powdered seeds to Sauvignon blanc in the pre-fermentative phase was effective in reducing the haze- forming proteins resulting in heat-stable wines. However, even though the fining treatment was effective in improving the

heat stability, the sensory impact on the resulting wine was not investigated. In a follow-up investigation (Romanini et al ., 2021), researchers focussed on the sensory effects of grape seed powder fining to determine the viability of such a treatment for the practical use in the wine industry. MATERIALS AND METHODS Sauvignon blanc and Sémillon juices were fined with grape seed powder (GSP) isolated from unfermented frozen Chardonnay grape marc. The seeds were roasted (180°C for 10 minutes) before refinement using a mortar and pestle (Romanini et al ., 2020). The refined product was added to the juices (20 L lots done in triplicate) at 20°C at two dosages, 7.5 g/L and 15 g/L. The GSP was in contact with the medium by stirring for one hour before it was removed by racking. The juice was then fermented, and the wine filtered and bottled for analyses.

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