Technical Yearbook 2023

Highlights • Nitrogen is a key element necessary for the synthesis of amino acids, nucleic acids, vitamins, and proteins in living organisms. • During grape juice fermentation, yeasts mainly utilise sugars, but can also use amino acids and ammonium salts to produce compounds that contribute to the aroma profile of the wine. • While most aroma compounds arise from sugar metabolism, supplementing certain amino acids and ammonium salts can impact the production of certain aroma compounds, including esters, higher alcohols and fatty acids. • Winemaking conditions, including temperature, pH, oxygen and availability of nitrogen and other nutrients, all influence the production of aroma compounds from nitrogen sources. • The production of aroma compounds varies greatly between species and strains. • It is permissible to increase the YAN of grape must by using ammonium salts only or yeast derived products.  References https://www.wineland.co.za/nitrogen-sources and-their-impact-on-aroma-production-in-wine/

acids, peptides and proteins) is allowed and has shown evidence of affecting the production of aroma compounds positively. Nevertheless, while most metabolic pathways leading to aroma production are known, there is much that is not understood. Research is ongoing regarding the complex interactions between nitrogen sources, yeasts and other nutrients, and the impact thereof on the production of aromatic compounds in winemaking. Abstract Nitrogen is an essential element for yeast metabolism, including the production of aroma compounds. Wine yeasts mainly make use of ammonium and amino acids to meet their nitrogen requirements, but these two differ in their availability to the yeast and their impact on the production of specific aroma compounds. The source of nitrogen also plays a role in the production of aroma compounds, including esters, higher alcohols and fatty acids. The Ehrlich pathway significantly contributes to the formation of aroma compounds in wine. During the fermentation, environmental conditions, nitrogen levels, and the selection of yeast species and strains have a significant impact on the production of aroma compounds. Therefore, understanding the impact and differences of the nitrogen source during fermentation can help winemakers optimise their processes to produce high-quality wines with the desired aromatic profiles.

For more information, contact Benoit Divol at divol@sun.ac.za.

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TECHNICAL YEARBOOK 2023