We recently had a conversation with professor and enologist Dr. Anna Katharine Mansfield on yeast assimilable nitrogen more commonly known as YAN and why understanding YAN levels is essential not only for winemakers but also for wine-grape growers. Below we recap five key things to know about YAN.
- Understanding YAN
YAN is made up of two key components – ammonium and amino acids. Nitrogen is essential for yeast during the fermentation process because it helps convert sugar into alcohol but is often overlooked. Many growers focus primarily on sugar, pH, and titratable acidity, but the relationship between nitrogen and yeast is just as important.
- YAN’s Role in Grape Growing
Understanding the level of YAN in grapes at harvest is crucial. The level of YAN can significantly impact the fermentation process. If YAN levels are too low, the yeast may not have enough nutrients to complete fermentation, leading to stuck or sluggish fermentations. If YAN levels are too high, this can also cause problems such as rapid fermentation, increased risk of microbial spoilage, and negative changes in wine flavor.
- Measuring YAN
Measuring YAN is not as easy as following one universal equation. The levels can vary between different vineyards, locations, and climates — and even within the same vineyard. It’s recommended that winemakers measure YAN levels annually to get an idea of what’s happening in their vineyard and how regional and seasonal conditions are affecting their grapes.
- Nitrogen’s Impact on Wine Quality
What happens during the fermentation process will affect the overall taste and quality of the wine. Therefore, it’s important that the nitrogen is measured correctly. Certain amino acids can be converted during fermentation into specific flavors. For instance, volatile thiols that give a wine its unique aroma come from amino acids. Therefore, a well-balanced nitrogen diet can result in a more flavorful wine.
- The Importance of Balancing Nitrogen
As with many things in viticulture and winemaking, balance is key when it comes to YAN. Both too high and too low YAN levels can cause issues. The goal is to understand the right amount of YAN for the specific type of wine you are producing and work towards achieving those desired YAN levels in the vineyard, but also knowing how and when to supplement YAN in the winery when needed. This balance is not only about adding nitrogen but also ensuring it’s available in the right forms (ammonium and amino acids) and at the right times for the wine yeast.
By monitoring and understanding YAN levels, growers and winemakers can improve the taste and quality of their wine. Listen to https://www.vineyardundergroundpodcast.com/vu027 to learn more about all things YAN.