WW ASB 16-02
Status of yeast assimilable nitrogen (YAN) in South African grape musts. Impact of cultivar and area
Stellenbosch University. Department of Viticulture and Oenology
Nitrogen concentration and composition of the grape and must has significant implications or wine quality. Grapes contain a variety of nitrogen containing compounds. Among the nitrogen sources available for yeast nutrition in grape juice, ammonium and free amino acids (FAN) are definitely the most important. These compounds constitute together what is commonly referred to as yeast assimilable nitrogen (YAN).
These compounds promote cell growth of yeast and affect significantly the winemaking process (e.g. fermentation rate, alcohol yield, residual sugars) and the sensory quality of wine. The latter mainly through the final volatile products of the fermentation metabolism of yeasts.
The YAN deficiency threshold is defined at 140-150 mg/L for Saccharomyces, but there are differences in the ability of the yeast for taking up the various constituents of YAN. An investigation of YAN levels and its various constituents are important in the winemaking process. The winemaker needs accurate analysis to determine, the amount and nature of the additions for optimal fermentation and wine quality.
Buica, A S and Bieszczad, N. 2016. Surveying white wine cultivars for YAN and amino acids in South African viticultural areas of the Western Cape. Poster presented at the 38th South African Society for Enology and Viticulture Congress, 23-25 August, Somerset West, South Africa.
Biesczad, N and Buica, A. 2016. Amino acid profiles of South African grape wine white cultivars. Poster presented at Wine Active Compounds, March 2017, Beaune, France.
Biesczad, N and Buica, A. 2016 Surveying white wine cultivars for YAN and amino acids. Poster presented at the Focus on Chenin blanc, October 2016,Rawsonville, South Africa.