By Branden Hamby
When thinking about the aromas of wine, most people focus on the fruity or floral sensations that arise from a glass; esters, specifically the acetate esters formed during the fermentation process, are responsible for the expression of those complex aromatics in wine. These esters are formed not only from the nitrogen sources, such as ammonium and amino acids, within the must, but also from the nitrogen found in nutrients used in winemaking.
“The esters have a substantial impact on the aromatics, they add complexity and quality to the expression of aromas through the degradation of yeast-derived amino acids found in the nutrients,” says Marco Bertacinni, Country Manager at AEB USA.
Trials, conducted by AEB, were set up by testing amino acid nutrients against other common nitrogen based nutrients to determine their impact on the aromatics of the wine. Four wineries participated in the trials and found a quantitative increase from the use of amino acid based nutrients in at least one of the trials by using gas chromatography to measure aromatic levels. The other three wineries began the trials during the 2017 harvest and are awaiting GC analysis to determine quantitative results.
Amino acids nutrient supplementation is one way to successfully supplement must to produce desirable aromatics through ester production. This method involves the Ehrlich Mechanism which shows the degradation of amino acids to produce esters. This pathway is more energy intensive but produces favorable aromatic esters such as ethyl acetate which gives more fruity aromas reminiscent of bananas or pineapples when at low concentrations.
Sensory analysis and evaluation was done on all the samples, and says Bertacinni, “There really is a difference in the aromatics by using amino acid based nutrients over the traditional supplements such as DAP.”
Diammonium phosphate (DAP) supplementation during fermentation is the other way to supplement must and is common in every winemaker’s harvest playbook. It is used to help raise assimilable nitrogen levels in the must (YAN) as well as help speed along fermentation. Ammonia is the least energy-demanding form of nitrogen available to yeast, this allows for amino acid biosynthesis to take place when DAP is supplemented in the must. Esters form from the intermediates of this biosynthesis.
Bertacinni will be moderating a session on The Influence of Nutrients on Aromatics at the WIN Expo, and he will be joined by a panel of winemakers to showcase his findings on the topic. The effects of nutrients on wine are significant, especially when it comes to aromatics, and the panel will discuss the pros and cons of using DAP and/or amino acid based nutrients as well as present a tasting comparing different wines and how the aromatics were influenced by the different nutrients.
The WIN Expo Trade Show and Conference takes place at the Sonoma County Fairgrounds in Santa Rosa, CA on November 30. For more information and registration, go to wineindustryexpo.com.