Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
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SUMMER 2012
WINEMAKING
Conclusions
These studies reveal complex interactions between nitrogen supplementation and grape- and yeast-derived aroma compounds, which can, however, be exploited to modulate wine aroma and style. Low YAN fruit provides the greatest opportunity for managing the flavor profile.
In general, musts with low available nitrogen reduce yeast growth and metabolic activity, which result in lower production of yeast aroma compounds, with the exception of the higher alcohols, to give a low aromatic intensity of more complex but less fruity attributes. Such musts are also at greater risk of slow or stuck fermentation and wines acquiring “reductive” attributes.
Added nitrogen, whether organic or inorganic, stimulates yeast growth and the production of aroma compounds, which intensifies perceived aroma. This also increases the balance of fruity and floral esters relative to the more savory higher alcohols, thereby masking complex aromas and emphasizing a fruity profile. This experimental result suggests that moderate use of DAP might produce a similar aroma profile to that which results from grapes with naturally higher YAN content. Results from the Albariño study further suggest that moderate DAP use can enhance some varietal compounds.
Large additions of nitrogen should only be made with great caution; when inorganic nitrogen is used, such as DAP, there is an increased risk of high residual phosphate and a large risk of excessive acetate production. Ethyl acetate, in particular, produces an undesirable “perceived volatile acidity,” solvent character, thereby masking desirable aroma attributes.
Addition of a large amount of organic nitrogen (an experimental mixture of amino acids and ammonium) significantly intensifies the fruity aroma profile, but the risk of masking varietal character remains an open question. However, it is not yet technically feasible, or even desirable, to use such large concentrations of organic nitrogen (most commercial preparations of organic nutrients, such as those derived from inactivated yeast, have low YAN content), except that which results naturally from high vigor vineyards.
While the investigation with Albariño suggests that YAN can also increase the varietal impact of wine, at least for some combination of varieties and yeast strains,6 the impact should not be overestimated. Furthermore, it should be noted that some yeast strains, such as AWRI 796, are highly responsive to DAP addition and therefore, in young wines, the high ester production can partially mask varietal character. Winemaker feedback suggests that such wines maintain fruit and varietal character during ageing better, however.
In order to best manage wine flavor it is necessary to determine the assimilable nitrogen content and use
DAP according to the style of wine required; winery trials are essential to determine whether DAP supple-mentation is beneficial with particular combinations of grape variety and yeast strain. Broadly similar flavor affects are also achieved in red wine varieties.5,7
   
[This text was first published in the Australian & New Zealand Grapegrower & Winemaker, June, 2012, and is edited and reproduced here with kind permission of the publisher, Winetitles.com.au.]
Acknowledgements
The authors acknowledge financial support by grants from the Spanish Government. Research at The Australian Wine Research Institute is supported by Australia’s grapegrowers and winemakers through their investment agency the Grape and Wine Research and Development Corporation, with matching funds from the Australian Government. The AWRI is a member of the Wine Innovation Cluster. Paul Henschke may be reached at paul.henschke@awri.com.au
References
1. Albers, E., C. Larsson, G. Liden, C. Niklasson, L. Gustafsson. 1996 “Influence of the nitrogen source on Saccharomyces cerevisiae anaerobic growth and product formation.” Appl. Env. Microbiol. 62: 3187-3195.
2. AWRI publication #852. Francis, I.L., J.L. Newton. 2005 “Determining wine aroma from compositional data.” Aust. J. Grape Wine Res. 11 (2): 114-126.
3. AWRI publication #875. Bell, S.-J., P.A. Henschke. 2005 “Implications of nitrogen nutrition for grapes, fermentation and wine.” Aust. J. Grape Wine Res. 11: 242-295.
4. AWRI publication #1001. Vilanova, M., M. Ugliano, T. Siebert, I.J. Pretorius, P.A. Henschke. 2007 “Assimilable nitrogen utilization and production of volatile and nonvolatile compounds in chemically defined medium by Saccharomyces cerevisiae wine strains.” App. Microbiol. Biotechnol. 77: 145-157.
5. AWRI publication #1093. Ugliano, M., T. Siebert, M. Mercurio, D. Capone, P.A. Henschke. 2008 “Volatile and color composition of young and model-aged Shiraz wines as affected by diammonium phosphate supplementation before alcoholic fermentation.” J. Agric. Food Chem. 56 (19): 9175-9182.
6. AWRI publication #1122. Ugliano, M., P.A. Henschke. 2009 “Yeast and wine flavour.” Moreno-Arribas, V., Polo, M.C. (Eds.). In Wine Chemistry and Biochemistry. New York: Springer, Chapter 8D, pp. 313–392.
7. AWRI publication #1256. Ugliano, M., B. Travis, I.L. Francis, P.A. Henschke. 2010 “Volatile composition and sensory properties of Shiraz wines as affected by nitrogen supplementation and yeast species: rationalizing nitrogen modulation of wine aroma.” J. Agric. Food Chem. 58 (23): 12417-12425.
8. AWRI publication #1277. Torrea, D., C. Varela, M. Ugliano, C. Ancin-Azpilicueta, I. Francis, P.A. Henschke. 2011 “Comparison of inorganic and organic nitrogen supplementation of grape juice – effect on volatile composition and aroma profile of a Chardonnay wine fermented with Saccharomyces cerevisiae yeast.” Food Chem. 127: 1072–1083.
9. AWRI publication #1290. Schmidt, S.A., S. Dillon, R. Kolouchova, P.A. Henschke, P.J. Chambers, 2011 “Impacts of variations in elemental nutrient concentration of Chardonnay musts on Saccharomyces cerevisiae fermentation kinetics and wine composition.” Appl. Microbiol. Biotech. 91 (2): 365-375.
10. AWRI publication #1373. Carrau, F.M., K. Medina, L. Farina, E. Boido, P.A. Henschke, E. Dellacassa. 2008 “Production of fermentation aroma compounds by Saccharomyces cerevisiae wine yeasts: effects of yeast assimilable nitrogen on two model strains.” FEMS Yeast Res., 8 (7): 1196-1207.
11. AWRI publication # 1375. Vilanova, M., T.E. Siebert, C. Varela, I.S. Pretorius, P.A. Henschke. 2012 “Effect of ammonium nitrogen supplementation of grape juice on wine volatiles and non-volatiles composition of the aromatic grape variety Albariño.” Food Chem. 133: 124–131.
12. Fugelsang, K.C., C.G. Edwards. 2007 Wine microbiology. Practical applications and procedures. New York: Springer, p. 117.
13. Hernández-Orte, P., M. Bely, J. Cacho, V. Ferreira. 2006 “Impact of ammonium additions on volatile acidity, ethanol, and aromatic compounds production by different Saccharomyces cerevisiae strains during fermentation in controlled synthetic media.” Aust. J. Grape. Wine Res. 12: 150-160.
14. Mendes-Ferreira, A., C. Barbosa, A. Ines, A. Mendes-Faia. 2010 “The timing of diammonium phosphate supplementation of wine must affects subsequent H2S release during fermentation.” J. Appl. Microbiol. 108 (2): 540-549.
15. Miller, A.C., S.R. Wolff, L.F. Bisson, S.E. Ebeler. 2007 “Yeast strain and nitrogen supplementation: Dynamics of volatile ester production in Chardonnay juice fermentations.” Am. J. Enol. Vitic. 58 (4): 470-483.
16. Osborne, J.P., C.G. Edwards,. 2006 “Inhibition of malolactic fermentation by Saccharomyces during alcoholic fermentation under low- and high nitrogen conditions: a study in synthetic media.” Aust. J. Grape Wine Res. 12: 69-78.
17. Torrea, D., P. Fraile, T. Garde, C. Ancin. 2003 “Production of volatile compounds in the fermentation of chardonnay musts inoculated with two strains of Saccharomyces cerevisiae with different nitrogen demands.” Food Control 14: 565–571.