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How Wine Yeast Benefits from NutrientsWhat are yeast nutrients?
| Why should I care about nutrients? 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 it. 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? 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:
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? Here's a short list of the various nutrients needed by wine yeast, and the benefits each provides:
Nutrient Dosage Rates and Timing A recent post on the Enologists web board by Ed Goist suggests the following dosage recipe:
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? If making wine from fresh or frozen juice (not processed - just
straight grape juice), here are the recommended doses of DAP and
Fermax™: If making wine from a wine kit*, the proper
doses would be: 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 Following our dosage recipe, we would add: 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 a Formol 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 temperature fermentations. 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 sell. Lallemand (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. Conclusion References Enologists
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