Yeast Nutrition: Amino Acids Are Better Than Ammonia (DAP)
The importance of an organic source of nitrogen
Last updated: 9/2021
Applies to: winemakers who are supplementing yeast available nitrogen (YAN) during alcoholic fermentation.
WHAT FORMS OF NITROGEN CAN YEAST USE?
Nitrogen plays a critical role in yeast metabolism. Nitrogen-containing compounds that yeast can utilize are naturally found in grapes. Often, the levels of these compounds are not high enough to secure fermentation and their levels must be supplemented with winemaking nutrients.
Nitrogen that is available for yeast to utilize is called yeast assimilable nitrogen (YAN). YAN comes in two main forms, amino acids and ammonia. These are referred to as organic and inorganic nitrogen, respectively. This simply indicates whether the compound also contains carbon (inorganic = no carbon, organic = contains carbon). When talking about inorganic and organic nitrogen, we prefer to directly address the nitrogen source:
Organic Nitrogen = Amino Acids and Peptides
In winemaking, organic nitrogen is supplied as amino acids and some peptides. Common winemaking sources are nutrients derived from autolyzed yeast.
Inorganic Nitrogen = Ammonia (NH3)
In winemaking, inorganic nitrogen is supplied as ammonia (NH3). Common winemaking sources are diammonium phosphate (DAP) and other ammonia salts.
WHICH IS MORE EFFICIENT?
Historically, diammonium phosphate (DAP) has been the yeast nutrient of choice for winemaking. In fact, most academic recommendations for YAN supplementation are based on DAP addition. However, nitrogen supplied as ammonia (DAP) is taken up very quickly which can lead to uncontrolled cell growth and hot fermentations and does not necessarily give yeast the staying power to complete a fermentation.
Alternatively, when nitrogen is supplied in the form of amino acids, the fermentation profile is very different. Ferments do not get as hot, the yeast population is controlled, and the cells are healthier. Interestingly, both aroma and mouthfeel are also improved when DAP is avoided.
While yeast may show an affinity for ammonia, a yeast diet balanced with amino acids can produce healthier fermentations, better aromatics (e.g. terpenes and esters) and lower levels of undesirable compounds (e.g. ethyl acetate and hydrogen sulfide).
Supporting Data: FERMAID O™ vs. DAP
Data represented are from trials done by Lallemand Oenology and the Institut Coopératif du Vin (ICV) in collaboration with the National Agricultural Research Institute (INRA) Pech Rouge Research Station in the Languedoc region of France.
The data above compares the effects on fermentation kinetics when nourishing with ammonia vs. amino acids. DAP served as the source of ammonia while FERMAID O™ served as the source of amino acids.
The trial musts and fermentation protocols were identical. The only difference was that one lot received an addition of the equivalent of 16 ppm of YAN in the form of DAP while another received a similar YAN addition from FERMAID O. This addition was split into two for both treatments, with the first addition added at the onset of fermentation and the second addition added at 1/3 sugar depletion. The control received no addition of nitrogen. The addition of YAN from FERMAID O resulted in a complete fermentation (Figure 2) in approximately 10 days (Figure 1). Further, the fermentation involving only DAP had a significantly slower conclusion and higher final residual sugars than the wine made with FERMAID O (Figure 2).
These trials support that nitrogen supplied as amino acids produce more efficient fermentations that are more likely to finish vs. nitrogen supplied as ammonia.
Creating a Yeast Nutrition Plan
As previously addressed, diammonium phosphate (DAP) has long been the yeast nutrient of choice for winemaking as well as research surrounding fermentation nutrition. Though, with better information about the impacts of DAP on fermentation kinetics, increasingly sophisticated autolyzed yeast nutrients have been coming to market. Furthermore, our understanding of creating a holistic nutrition regime has evolved to include:
To conduct a healthy and complete fermentation, yeast not only require nitrogen, but minerals, vitamins, fatty acids, and sterols. Minerals, vitamins, fatty acids and sterols can be provided by a rehydration nutrient (GO-FERM PROTECT EVOLUTION™).
Beyond fermentation kinetics and security, certain yeast nutrients have the ability to also stimulate specific metabolic pathways resulting in increased wine aroma. The STIMULA™ range of nutrients both supplies nitrogen (as amino acids) and stimulates metabolic pathways to increase aromas and flavors. We recommend using STIMULA in combination with FERMAID O™ for complete fermentation nutrition.