Advanced Nutrients in Meadmaking

Travis Blount-Elliott

[Last Edited: 11/13/2021]

Questions or Comments:

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Quick Link to Spreadsheet

Preface

        I’m writing this because I spent many good hours on the Internet looking at forum posts, Reddit, PDFs, and manufacturer data sheets in the name of finding definitive answers about yeast nutrition. Every step of the way I was frustrated by the lack of actionable information compiled in one location. So, hopefully, here it is! Everything you need to know to answer the oft-repeated question, “How much nutrient should I add to my mead?”

When most people start making mead, they follow a set of instructions to add nutrients to their musts. This is usually learned by rote and accepted. That’s fine; it works! You can make an inexact science of nutrient additions, and the yeast will chug right along. There may come a time, however, when - for the purpose of going commercial, experimentation, or simply being very serious about the hobby - a mead maker will desire to gain a better understanding of how much nutrition to add to his must, what type, and when. This white paper is an attempt to bridge the gap from rote repetition to understanding the simple principles behind deciding how much of a given nutrient to add to one’s must.

Lastly, I add the caveat that I have examined this question primarily from the perspective of nitrogen requirements and nearly ignored the necessity of micronutrients. This is partially because I understand micronutrients to a much lesser degree, and partially because if you have enough nitrogen from the right sources, you’re probably okay in terms of micronutrients, too. If you want to quibble about the “advanced” in the title, you’re probably right. There’s much more to get into beyond this. It is certainly a relative term.

I am updating this document as I obtain new information. If something sticks out to you as incorrect or incomplete, please message me on Reddit; my username is at the top of this document. (And seriously, report the typos!)

Definitions

        There are a few terms I should define before I get started. Please read these, as I make some notes on my usage.

YAN: Yeast Assimilable Nitrogen. This refers to nitrogen in a must that yeast can use to metabolize sugars into alcohols.

Nutrient: nutrient, energizer, booster, etc. I will only use the word “nutrient” when I’m talking about an additive designed to add YAN and/or micronutrients to a must.

Micronutrients: Trace vitamins and minerals that yeast absorb, consume, etc for healthy growth and development.

PPM or mg/L: Parts Per Million or Milligrams Per Liter. These two terms are interchangeable. You can read why this is true, below.

Organic: I’m going to use this term exclusively in the scientific sense unless specifically noted otherwise: “of, relating to, or derived from living matter.” (thefreedictionary.org, Dec 2013)

Gravity: In this paper, whenever I refer to gravity, unless otherwise specified, I am referring to a must’s original/starting specific gravity.

PPM - Parts Per Million

This works just like it sounds – it is a comparative unit of measurement that refers to how many parts of Substance X are contained in one million parts of a composite Substance Y. For us, Substance X is YAN and Substance Y is our mead must. It is important to realize that we’re not (in our case) counting atoms; PPM is discussed in terms of unit per unit, where both units measure the same quality (volume, weight, etc). For our purposes, we deal only with weight.

PPM can be most intuitively understood with a couple of examples. The blogger from ElectroMeadSmith.blogspot.com wrote just such examples in April 2012, which I reproduce here, edited, and regrettably without permission, as the blog appears to be defunct. Please see the original pxost for more examples.

In the context of water at least, all this [PPM] is the same as saying milligrams(mg) per Liter(L). Let me show you how I got there:

• 1 ml of water weighs ~1 gram. This is a fact. Water has a Specific Gravity of 1.000 so that means 1ml of it has a mass of 1 gram
• 1 Liter of water = 1,000ml = 1,000g
• 1 mg (milligram) = 0.001 grams
• So if there is 1mg (0.001g) of some substance in 1 Liter (1000g) of water then there is 1PPM (0.001g/1000g=0.000001)

You have 1 liter of sugar-water solution containing 10g of sugar. How many PPM of sugar is present?

• 10g of sugar  = 10,000mg of sugar (1g=1000mg)
• So now we know that PPM is the same thing as saying how many mg per liter:

10,000mg/1 L = 10,000 PPM.

YAN Part I – Yeast Assimilable Nitrogen

YAN is expressed in PPM and refers to the amount of free primary amino nitrogen and ammonia-based nitrogen present in a must. As you probably already know, honey is particularly low in nutrients. This holds especially true of YAN. According to Ken Schramm in The Compleat Meadmaker, few unaugmented traditional mead musts will top 30 PPM. There are ways to test for nitrogen content, but these are not widely available to the home winemaker. Most people would have to send samples off to a lab. It’s safe to assume that a mead must has less than 25 PPM YAN.

There is a large acceptable range for YAN in a must, ranging loosely from 150 to 400 PPM. This depends on the gravity of the must, the yeast used to inoculate, and the natural YAN found in ingredients. In general, higher gravity musts require larger amounts of nitrogen to progress healthily through fermentation. The following suggestion has been thrown around for years.

Table: Outdated YAN PPM Requirements

These guidelines will work, but are outdated and inefficient. Scott Labs asserts that the numbers that are so often quoted as appropriate YAN PPM targets were unnecessarily high, and that improved materials, methods, equipment, and additive formulae, coupled with a better understanding of the fermentation process, have caused their experts to reduce estimates for how much YAN is necessary to completely and healthily ferment a mead.

Ken Schramm (of The Compleat Meadmaker and Schramm’s Mead) seems to agree. To paraquote him from a personal conversation circa 2015, “I’ve long felt that we mead makers have been over-nutrifying our musts.” He went on to say that if one were to read his recent publications carefully, one would notice that although he still states these traditional PPM YAN numbers, the numbers in his recipes add up to less than 200 PPM YAN in actuality.

The above recommendations also don’t take into account that some yeast strains have particularly high or low nitrogen requirements - information which can be obtained from most manufacturers.
        Can you add “plenty” and get away with it? Yes, kind of. There are legal limitations for commercial mead makers and practical limitations caused by detectable off-flavors. Too much nitrogen will also lead to a hot, rapid fermentation, and spikes in yeast activity which produce fusel alcohols - the infamous homebrew jet fuel flavor. Faster fermentation can also lead to a higher concentration of ethyl carbamate, which is a probable carcinogen according to the International Agency for Research on Cancer.

YAN Part II – Calculating YAN Requirements

        Scott Labs makes several publications available to winemakers each year. Among the most useful of these is the Fermentation Handbook, which is updated yearly. It’s primary purpose is to provide succinct documentation on their products, but also reflects their latest fermentation research. According to the Scott Labs 2016 Winemaking Handbook (page 36), the following formulae can be used to calculate must nitrogen requirements in PPM:

For Extra Low N requiring strains: Sugar (g/L) x 0.5†

For Low N requiring strains: Sugar (g/L) x 0.75

For Medium N requiring strains: Sugar (g/L) x 0.90

For High N requiring strains: Sugar (g/L) x 1.25

†This is actually from the 2015 handbook, which notes that a .5 multiplier is the lowest range. For some reason this information was removed from the 2016  handbook.

To calculate the grams per liter of sugar in your must, you need to take a specific gravity and Brix reading with your hydrometer. Most brewing hydrometers have both scales, but if yours doesn’t, use an internet calculator to derive the unknown value. Then plug the numbers into this formula:

        Sugar g/L = Brix * Specific Gravity * 10

1° Brix is defined as 1 g of sucrose in 100 g solution. Specific gravity is the ratio of a solution’s density to water’s density. We’ll multiply the Brix definition’s units by ten to show that 1° Brix is equivalent to 10 grams of sucrose in 1000 grams (1 kg) of sugar-water solution. This kilogram of solution will, however, have less volume than 1 kg of water (1 L) - remember, we’re looking for grams of sugar per liter - because it’s partially sugar by weight, and sugar has a higher density than water. The specific gravity of the solution, however, is the ratio of our substance’s density to that of water, so we can simply multiply by it.

I’ve described this here in detail because the Scott Labs 2016 handbook provides an incorrect formula for deriving Sugar (g/L). Scott Labs’ stated formula is Sugar g/L = Brix * 10. This might be a reasonable shorthand for weaker must or wort, but it will be off by more than 10% for strong mead must.

As an example, assuming that you have a mead with a specific gravity of 1.108 (25.5 Brix), in which you plan to use Lalvin 71B-1122 (low nitrogen requirements), we can do the following calculations:

25.5 * 1.108 * 10 =  282.5 g/L sugars

282.5 g/L sugars x 0.75 = 212 PPM nitrogen

Note: As of the 2020 Winemaking Handbook, they have simplified their recommended yeast requirements equations. These guidelines appear to be a derivative of the 2016 formulae, and yield the same results, which do not take the specific gravity into consideration.

Low nitrogen-requiring yeast need 7.5 ppm YAN per 1°Brix.

Medium nitrogen-requiring yeast need 9 ppm YAN per 1°Brix.

High nitrogen-requiring yeast need 12.5 ppm YAN per 1°Brix.

        In summary, this is the formula

                Required PPM N = Brix * Specific Gravity * 10 * [yeast multiplier]

So, where do we get all that nitrogen? Read on.

Nutrient Additives

There are several “nutrient” blends available to the homebrewer today. Some of the most popular and well-regarded of these are the line produced by Lallemand/Scott Labs, which includes GoFerm PE, Fermaid K, and Fermaid O, among others. Another common additive, Diammonium Phosphate, is available from a variety of sources. In this paper I will concentrate on these four additives.

There are also additives sold by L.D. Carlson labeled “nutrient” and “energizer.” I’ve had trouble finding reliable composition information on these additives, and have therefore shied away from their use. If you want to use them with the spreadsheet linked in this document, however, you can probably safely assume that they are roughly equivalent to Diammonium Phosphate (“nutrient”) and Fermaid K (“energizer”), but you probably should not use them in a commercial capacity without more information.

        First, let’s talk about what the Scott Labs additives contain in terms of nitrogen. In the previous section, I wrote that yeast can use primary amino nitrogen and ammonia-based nitrogen. Primary amino nitrogen is sometimes referred to as “organic nitrogen.” Conversely, ammonia-based nitrogen is “inorganic nitrogen.”

[Note: You may have seen, or might see the term “FAN” during your research. This stands for Free Amino Nitrogen, and it’s more frequently discussed in the context of winemaking with grapes. It refers to what I am calling “organic nitrogen.” Grape juices contain significant quantities of amino nitrogen, so it is beneficial to know how much of each is already present before supplementing the must with additives. It seems to be a somewhat dated term, though plenty of winemakers still use it. YAN = FAN + Inorganic Nitrogen]

For a discussion on these, I turn to Deezil, a user and moderator of the WineMakingTalk forums. With the help of another user, Seth8530, he compiled a lot of information on yeast nutrients. He writes:

Yeast prefer ammonia-based nitrogen, but that's not to say we should be supplying it. When yeast are given the opportunity to feed on ammonia-based nitrogen sources, the yeast population will increase more rapidly due to a 'feeding frenzy'. This does several things, which all reflect on each other; increase in yeast population leads to an increase in internal must temperature, and these factors then lead to excess expulsion of aromatics, and in the end lead to a larger die-off.

[...]

Organic, amino-based nitrogen sources are less-favored than ammonia-based sources by yeast, but they are the healthier option. It may only take as little as 1/3 the amount of organic nitrogen (by YAN) to finish the same fermentation as it would with an ammonia/DAP-based nutrient source.

What this means is that the yeast better-utilize the organic amino-based nutrient sources, due to the fact that the yeast have to perform a more-complex set of operations to metabolize this nitrogen. Those 'spikes' seen with ammonia-based nutrients, are instead more 'hill'-like, and this more-complex form of metabolism creates stronger, healthier yeast. Also, yeast will metabolize an amino-based nutrient well past the point where they stop with ammonia-based nutrients.

After about ⅔ of the way through a fermentation†, adding additional DAP-based nutrients is only fuel for spoilage organisms‡; the yeast can't assimilate these ammonia-based nitrogen past that point, no matter how addicted to it they are. They can however, still assimilate organic, amino-based nitrogen forms - although it is still possible to add too much, leaving excess behind for spoilage microbes.

[Reproduced with permission.]

[ † According to Scott Labs, yeast cease to be able to utilize ammonia based nitrogen (DAP) when their environment reaches 9% ABV, not necessarily at 2/3s the way through fermentation.]

[‡ According to Scott Lab’s Nichola Hall, leaving nutrients for spoilage organisms is not a concern - the yeast will consume as much ammonia based nitrogen as you give it - the ferment will just be hotter and faster.]

With this in mind, let’s look at the aforementioned nutrient additives:

See this document for average densities of these substances. If you don’t have a gram scale, you can use this for converting weight to volume.

Staggered Nutrient Additions (SNA)

        As Deezil wrote, inorganic nitrogen causes inordinate fermentation spikes as the yeast can use the easily available nitrogen to metabolize sugars very rapidly. This causes high temperature spikes in the fermenting must, and high and/or unstable temperatures are the enemy of a good clean fermentation. This problem is the origin of the idea for Staggered (or Stepped) Nutrient Additions (SNA), sometimes also called a Nutrient Addition Schedule (NAS).

        The idea is simple: if you add the nitrogen in small steps, the spikes will be smaller and affect the mead much less, creating a more linear fermentation that finishes cleaner with fewer fusel alcohols, and the mead will require less aging before reaching a point of reasonable drinkability.
        However, yeast cannot assimilate ammonia based nitrogen at all after the must reaches an alcohol content of roughly 9%. Because of this, all inorganic nitrogen needs to be added well before that mark to give the yeast time to metabolize it while they can still use nitrogen from such a concentrated and cheap source. Most SNA schedules call for a mixture of all nutrient additives to be split into 2-6 equal parts and added during aeration‡ for the first one third to one half of fermentation. Note, however, that the yeast will, in this case, metabolize the inorganic nitrogen first.

        Some schedules call for one or two nitrogen source shifts. These usually start with rehydration in GoFerm, then a post-lag dose of organic nitrogen to create a robust culture of yeast. Next, still early in fermentation, the rich and cheap inorganic sources are used. Finally, the remaining organic sources can be added throughout the rest of active fermentation.

        Another variation calls for using all of the organic nitrogen (Fermaid O) post-lag in one or two additions, then using a blend of Fermaid K and DAP at intervals through the first ⅓ to ½ of fermentation.

Be aware that yeast making the switch from an inorganic to organic nitrogen source will enter a lag phase while they acclimate to using their new nitrogen source. In this case the fermentation has probably not stalled – give it some time to switch over.

There are as many variations on SNA as there are meadmakers that use SNA. Only you can find a schedule and additive combination that meets your needs. Remember a few main principles:

• By breaking up nutrients into multiple additions you’re reaping major benefits
• At 9% ABV, the yeast can no longer benefit from inorganic sources
• Abide by nutrient limitations (if you so desire).

[ ‡The subject of aeration is slightly outside of the scope of this document. Aeration/degassing is optimally performed twice daily for the first ~1/3rd of fermentation. I recommend Googling “mead aeration” for more information and diverse opinions.]

        My preferred SNA schedule for using Go-Ferm PE, Fermaid O, Fermaid K, and DAP:

1. Rehydrate dry yeast with Go-Ferm PE as directed, just prior to pitch.
2. After the lag phase, about 24 hours after pitch, at first signs of active fermentation, add Fermaid O. This can be added in 1 or 2 additions. If two, wait 24 hours between additions.
3. Blend the required amounts of DAP and Fermaid K and split into 2-3 additions. Add at 24 hour intervals after final Fermaid O addition. The number of additions will depend on fermentation progress; the goal is to add the last DAP well-before the mead reaches 9% ABV.

Spreadsheet & Meadmakr.com Advanced Nutrient Calculator

I created a simple spreadsheet to help myself and others decide how much of each given additive to use. I have shared it here on Google Drive. You will need to make a copy of this document to use it. Further instructions can be found on the spreadsheet itself.

You can also find a calculator derived from my spreadsheet at www.meadmakr.com - both in the Batch Buildr and Advanced SNA Calculator. Meadmakr.com is run by Allen Jones, who has used my work with permission.

Note that because there is a lot of variation in how much yeast different mead makers pitch, I did not bother making it possible to calculate YAN from GoFerm. If you’d like to include this amount, you can calculate it yourself and add it to the offset. A quick rule of thumb is that if you’re using 2 g of yeast per gallon of must - the standard pitch rate - and rehydrating in the correct amount of GoFerm (grams of yeast * 1.25), you’re adding approximately 20 PPM nitrogen. If you use a whole 5 gram packet of yeast and 6.25 grams of Go Ferm on a single gallon of must, however, you’re adding over 50 PPM. Keep in mind that some dry yeast packets are 11.5 grams, or some other weight entirely.

Thank You

MarsColonist of Reddit’s /r/Mead and Meridian Hive Meadery

For setting me straight when I was a newbie.

I was so dumb, and he was so patient.

JamesAGreen of Reddit’s /r/Mead and Schramm's Mead.

        For being awesome and setting me up to meet with Ken.

Ken Schramm of Schramm's Mead

        For talking to me for far too long.

Deezil and Seth8530 of WineMakingTalk.com

        For letting me quote their posts.

ElectroMeadSmith (whoever you are!)

        If you ever see this, consider this an official request to use your post on calculating PPM.

Scott Labs employees Dr. Nichola Hall and Brooke Jennett

        For very patiently responding to emails and phone calls.

Allen Jones of Meadmakr.com

        For both citing my work on Meadmakr.com and allowing me to provide related input.

        For helping me with the calculation to determine sugar g/L from SG and Brix.