Technical Yearbook 2024

AUGUST

Towards a circular economy in winemaking – re-utilisation of yeast lees By Karien O’Kennedy

Environmental sustainability and the circular economy are gaining importance in agricultural industries globally. Consequently, South Africa Wine dedicates significant resources to funding research projects focused on these critical areas. Additionally, South Africa Wine prioritises the transfer of knowledge and technologies (local and international) related to environmental sustainability and the circular economy to enhance the effective implementation of advancements within the industry. Yeast lees as yeast nutrients The art of winemaking is steeped in tradition, yet innovation continues to push the boundaries of what is possible. One of the latest advancements comes from a team of Australian researchers who have turned a common by-product of winemaking, yeast lees, into a valuable resource that can enhance subsequent fermentations. Researchers explored the feasibility of using processed yeast lees generated during alcoholic fermentation as a nutrient supplement in subsequent fermentations. The addition of processed yeast lysates into grape juice was shown to improve fermentation

timeframes and influence the production of yeast-derived fermentation volatile compounds in a dose-dependent manner. This study demonstrates that recycling spent lees from winery waste is feasible and provides some strategies for extracting nutrients from winery waste. The role of nitrogen in fermentation Nitrogen is a critical nutrient for yeast during the fermentation process. It influences the growth and reproduction of yeast cells and the speed and efficiency of fermentation. Nitrogen is essential, because it supports the synthesis of proteins, nucleic acids and other cellular components within the yeast cells. Without enough nitrogen, yeast cells can become stressed, leading to incomplete fermentation and the production of undesirable compounds that can affect the flavour and aroma of the wine. Winemakers often supplement grape musts with nitrogen sources to ensure a healthy fermentation process. Common supplements include inorganic nitrogen salts like diammonium phosphate (DAP) and organic nitrogen compounds like yeast cell lysates. The untapped potential of yeast lees In addition to producing wine, the fermentation process generates a significant amount of nutrient-rich biomass known as lees. This sediment, which includes dead yeast cells, grape solids and other particulate matter, is typically discarded or used in low-value applications. However, this study explored the potential of recycling yeast lees as a nutrient source for subsequent fermentations.

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TECHNICAL YEARBOOK 2024