How Wine Yeast Benefits from Nutrients
What are yeast nutrients?
| Why should I care about nutrients?
Nutrient dosage rates and timing | Conclusion
Imagine that you're about to participate in a great test of physical
endurance - the New York City Marathon. Would you attempt such a
feat knowing you hadn't eaten anything the night before? Of course
not! And yet, without realizing it, many home winemakers are asking
their yeast to perform a similar Herculean task without the benefit
of basic nourishment.
From the perspective of wine yeast, it takes a lot of energy to
fully ferment a quantity of grape juice into wine. As concerned
winemakers, we must do our utmost to ensure the fermentation environment
provides all the nutrients the wine yeast needs - when it needs
This winemaking article will explain the ins and outs of adding
nutrients to your wine - how much to add, and when to add it.
What are yeast nutrients?
For our purposes here, we'll broadly define a "nutrient"
as anything your wine yeast needs in order to survive, ranging from
food, vitamins, and chemicals to the air and everything in between.
Luckily, yeast nutrients are inexpensive and easy to obtain for
the home winemaker. They come packaged in a variety of formats.
The most common formats are described below:
- DAP (Diammonium Phosphate) - Contains fermentable nitrogen
(N) at 25g/HL = 50mg/L N and phosphorus. The chemical formula
for DAP is (NH4)2HPO4. For instance, a DAP
addition of 1 g/L (8.3 lb/1,000 gal) provides about 258 mg/L fermentable
- Fermax™ - contains diammonium phosphate, dipotassium
phosphate, magnesium sulfate, autolyzed yeast. Grapestompers.com
stocks this popular nutrient "cocktail".
- Fermaid - Also called Fermaid K. Contains a variety of
compounds such as amino acids, sterols, yeast hulls, and vitamins;
also contains a limited concentration of fermentable nitrogen
(25g/HL = 25 mg/L fermentable N)
- Yeast Hulls - The cell walls of the hulls absorb autotoxic
yeast byproducts that could inhibit alcoholic and malolactic fermentations.
You would use yeast hulls by themselves if you encountered a stuck
or sluggish alcoholic (normal) or malolactic fermentation.
Note: The rules allow an addition of 8 lbs of DAP per 1000 gallons
of wine, but in addition, the full amount of vender's recommendation
of proprietary mix (Fermax™, Fermaid, etc.) is also allowed.
Why should I care about yeast nutrients?
If your wine doesn't have enough nutrients in it for the yeast to
work, you might end up having a stuck
fermentation. Worse yet, you may even ruin your wine due to
hydrogen sulfide contamination
(a symptom of which is a "rotten egg" smell) caused by
a lack of nitrogen and a vitamin known as pantothenic acid.
Here's a short list of the various nutrients needed by wine yeast,
and the benefits each provides:
- Nitrogen - Nitrogen produces the protein needed to make
new yeast cells.
- Oxygen - Oxygen is required during the initial phase
of fermentation to help the yeast cells multiply rapidly, thus
giving your fermentation a good kick start. The yeast also needs
oxygen to produce lipids in their cell walls, to provide protection
against the alcohol toxicity near the end of fermentation. The
best way to accomplish the introduction of oxygen is to leave
off the airlock for the first couple of days.
- Micronutrients - The term given to various trace vitamins
and minerals needed in small quantities, such as phosphorus, urea,
amino acids, pantothenic acid, citric acid, biotin, yeast hulls,
Nutrient Dosage Rates and Timing
There's definitely a right way and a wrong way to add nutrients
to your must or wine. This is one time you don't want to
do a "dump and run" by throwing in the complete dose of
nutrients at one time at the start of your batch. Recent studies
show that spreading the nutrient doses out over time - that is,
properly spaced apart - can greatly benefit your wine. Moreover,
there is evidence that suggests when DAP should be added versus
Fermax™ or Fermaid K.
A recent post on the Enologists
web board by Ed Goist suggests the following dosage recipe:
- Before yeast addition: Add 50% of DAP dose and 33% of
- Once fermentation starts: Add 50% of DAP dose and 33%
of Fermax™ dose
- At 12-8° Brix: Add the final 33% of Fermax™
Dosage charts are shown below.
We add our doses in this way because one large initial dose of
DAP may delay or inhibit the uptake of amino acids by the yeast
cells. Also, if nitrogen is added too late, the cells can't uptake
the nitrogen due to the presence of alcohol. Adding nutrient supplements
such as Fermax™ or Fermaid K all at once can lead to too fast
of a fermentation rate and an imbalance in uptake and usage of nitrogen
compounds. Supplements added too late (after half the fermentation)
may not be used by the yeasts, partly because the alcohol prevents
their uptake. Thus, we spread out the doses over time it so the
wine gets what it needs when it needs it.
What is a proper dose of DAP and Fermax™ for a wine?
The answer largely depends upon the source and quality of your juice.
In general, if you press your own grapes or buy fresh or frozen
juice from a vineyard, your doses will be higher than if you make
your wine from a wine kit.
If making wine from fresh or frozen juice (not processed - just
straight grape juice), here are the recommended doses of DAP and
- 1 gram DAP / liter
- 1 gram Fermax™ / US gallon
If making wine from a wine kit*, the proper
doses would be:
- 0.2 to 0.4 grams DAP / liter
- 0.1 to 0.2 grams Fermax™ / US gallon
For example, let's say you have 6 US gallons of fresh grape juice
from your backyard that you want to make into wine. Based on the
chart above, your recommended doses would be calculated like this:
1 US gallon = 3.79 liters, so 6 gallons = 22.71 liters
Total DAP dose: 22.71 grams
Total Fermax™: 6 grams
Following our dosage recipe, we would add:
- 11.35 grams of DAP and 2 grams of Fermax™ before adding
- 11.35 grams of DAP and 2 grams of Fermax™ once fermentation
- 2 grams of Fermax™ at 12-8° Brix
During our research for this article, we've discovered that the
bare minimum level of fermentable nitrogen needed for fermentation
is 140 mg/liter; the normal range is considered to be between 225
and 275 mg/liter of fermentable nitrogen.
A more exact means to determine the proper amount of nitrogen (and
thus DAP) to add is to first measure the amount of nitrogen that
is available in your must. You can calculate this value by performing
titration. After you know how much nitrogen is in your must,
you can easily figure out how much more you might need.
*Some juice in cheaper wine kits can be
very low in nutrients and low in solid matter that usually assists
in keeping the yeast in suspension even during active fermentation.
Another factor to consider regarding juice from concentrate and
kits is the fact that there is usually very little to no insoluble,
particulate matter present. The absence of particulate matter allows
the yeast to settle rapidly during the period that there is very
little fermentation activity. This is especially true with cool
We've never experienced the problems described above with the
kits made by RJ Spagnols. Tom has spoken with their staff to ensure
the proper amounts of nutrients are present in each wine kit we
(a manufacturer of wine yeasts) recommends stirring the must several
times during the first 24 - 48 hours and again during the last days
of fermentation to keep the yeast up in suspension where all of
the action is.
Nutrients for wine yeasts - when added in the proper amount and
at the correct time - will go a long way towards preventing common
problems (such as stuck fermentations and hydrogen sulfide contamination)
and help ensure your wine ferments fully and without difficulty.
Nutrients are available in several formats and are inexpensive to
purchase; with a little knowledge and basic math skills, it's easy
to determine the proper dose of nutrients to add.
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