Wine yeast have a high demand for nutrients, not only during rehydration, but throughout fermentation. Fermentation nutrients are a class of products specifically designed to help remedy deficiencies the juice/must may have.
What is Deficient?
This is always the first question to ask. Nitrogen deficiency is the most common and talked about issue with fermentation problems. Fortunately, it is relatively easy to analyze and remedied using additives such as diammonium phosphate (DAP).
Micro-nutrients refers to various compounds naturally occurring in grapes, including sterols, lipids, vitamins, and minerals. These are often deficient in juice/must, but very rarely identifiable prior to fermentation. Problems with can usually be guaranteed for grapes that have a history of deficiency or grapes that have been subject to poor growing conditions, such as mold or rot. Still, winemakers have a far more difficult time forecasting potential threats to successful fermentation and subsequent negative effects on wine quality.
Fermentation nutrients are specifically aimed to provide yeast with micro-nutrients. They can be classed in two different categories: complex yeast nutrients and vitamin supplements.
Complex yeast nutrients
These proprietary blends of nutrients include products such as Fermaid K/O, Bioactiv, and Superfood. They provide several nutrients at varying levels, primarily derived from autolyzed yeast cells.
- Many provide nitrogen, whether inorganic, organic, or a combination.
- Lipids, otherwise referred to as fatty acids.
- Vitamins which may include thiamine, biotin, and niacin.
The cell wall structures provided by the autolyzed yeast also play important roles during fermentation.
- Absorb medium-chain fatty acids that are toxic to yeast, helping prevent alcohol toxicity and yeast stress.
- Provide nucleation sites, helping keep the yeast in suspension throughout fermentation.
Winemakers have varying views on when, why, and how to use complex yeast nutrients. These decisions are often made using expense consideration.
- Only for juice/must destined for higher price-point finished products. This is particularly relevant in large-scale wine production.
- Only for ferments that already display problems, such as stuck ferments.
- Using a combination of two products. For example, Superfood is significantly less expensive than Bioactiv.
- Completing multiple additions at different stages of fermentation.
Some suppliers will purchase specialized individual vitamin supplements, while commercially available products include Cerevit and Vitamix. These provide an array of key nutrients such as thiamine, biotin, nicotinamide, magnesium sulphate, calcium panthothenate, and folic acid. Many of these micro-nutrients are contained in complex yeast nutrients, but can remain at deficient levels depending on the state of the juice/must.
Again, winemakers all have varying views on when, why, and how to use vitamin supplements. The primary concern to keep in mind is making sure that legal levels of certain micro-nutrients are not exceeded, particularly when using vitamin supplements in conjunction with out yeast nutrients. For example, Cerevit added at its recommended rate contains the legal limit of calcium panthothenate for most countries. Used in conjunction with Bioactiv, the resultant wine will be above legal limits.
I personally recommend using vitamin supplements as a safety precaution whenever there is a hint of a problem during higher-end wine production.
- Their cost will not make a significant increase to production expense.
- They do not directly effect aroma/flavor. Basically, they will only production of undesirable compounds due to yeast stress.
- Peace of mind. You won't regret using it, but you very well may regret not.