I think common practice is over feeding our little ones!

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I have another question to add to the mix. This is an intensely interesting discussion! Love of Rose, if yeast can only uptake DAP up to 9-10% alcohol, how would the home Mead maker calculate the correct amount of DAP to add at the beginning so that by the time the yeast could no longer uptake it, all of the DAP had been consumed and none would be remaining that might be tested in the final product?
 
I got chills when I read that. "Better brewing through science," indeed! :D

Bray, if someone were using the TOSNA protocol would you advocate throwing in some DAP at the beginning of fermentation as well? I seem to recall Oskaar saying that when yeast switch between using amino and inorganic nitrogen sources they undergo a lag phase, but can't remember where he might have said it. Would the extra lag phase be a stress on the yeast? How do the yeast respond metabolically to having both sources of nitrogen available at the same time? Can the pathways that process amino and inorganic nitrogen only run one , or can they also run in parallel?

It seems yeast will not do anything to amino acids while ammonium is present. Oskaar suggests using dap up front to get the ferment up and running faster, giving less opportunity for wild organisms to take hold.
"The sequence of amino acid accumulation is influenced by the presence and relative abundance of various nitrogen compounds, especially the ammonium ion, and possibly the total nitrogen concentration (Rose, 1987). In model media fermentations (4.87g amino acids/l; 785mg N/l) supplemented with ammonium ions (155mg N/l) , the apparent sequence of amino acid utilization was no longer evident (Jiranek et al. 1990). The initial accumulation of ammonium ions from the medium commenced most rapidly at the expense of both Group A and B components, the sccumulation of which was slightly delayed and largely incomplete..."
There are 2 transport systems for ammonium, one which is probably bidirectional, whatever that means. Ammonium leaves the cell again once the charge outside the cell changes? "The second system is one of passive or facilitated diffusion which operates at external urea concentrations of greater than 0.5mM, and is probably bidirectional in function."

I think yeast do not 'prefer' ammonia, but are unable to consume anything else whild there is a significant amount of ammonia present.
Meanwhile:

"At least 11 transport systems specific to L-amino acids have been identified". Then there is an aditional General Amino Acid Permease (GAP). Gap works at the later stages when there is little nitrogen available because it is a scavenging transport system and does not work in the presence of ammonia. A group of AA can only be metabolised with this system. Not all transport systems can work at the same time.
The study continues by saying that ammonia is good, but AA are 'preferred'
"Typically the 'preferred' amino acids namely those largely taken up early in fermentation, support high growth rates when supplied as sole nitrogen sources. Thus, the sequence of amino acid accumulation and the extent to which individual amino acids contribute to total nitrogen requirements are functions of the closeness with which the amino acid matches the criteria of a good nitrogen source. However, mixturesof amino acids, as occur in musts, generally support faster rates of growth and fermentation than do single compounds. The functioning of a number of transport systems increases the rate and diversity of nitrogen accumulation and reduces the need for amino acis catabolism for biosynthesis of deficient compounds."

Catabolism is the breaking down of molecules. So if fermaid O were composed of a single type of amino acid yeast might need to break it down, but if fermaid O is complex enough it might not need to.

A nitrogen compound could be utilized:
- without modification e.g an amino acid is incorporated directly into protein.
- as a source of nitrogen e.g an amino acid is degraded to liberate nitrogen for the biosynthesis of other nitrogen cell constituents; the carbon skeleton may be excreted from the cell
- as a source of carbon e.g the carbon component of an amino acid is released and used for the biosynthesis of other carbon cell constituents
The metabolic efficiency of a nitrogen source depends on the expression, regulation and efficiency of transport systems as well as the regulation and energetics of subsequent catabolic and anabolic processes. Consequently, growth, fermentation rate and biomass yield will depend on both the quantity and the nature of the nitrogen sources available."

So amino acids are not always simply turned into nitrogen. This article/book also talks about different efficiencies. Not all nitrogens are the same, which is why simply calculating yan for amino acids is not sufficient

Info taken from https://books.google.com.mt/books?i...bolism of nitrogen compounds henschke&f=false
 
P.s I have hardly read this stuff enough to pretend I fully understand. I would not be surprised if someone else were to read through it and prove some of my conclusions wrong
 
Actually, all the above is what I said in the first post. I try to make it easier to understand for you guys. The information is useless if you cannot decipher it!

This also supports the idea that adding both DAP and Fermaid O upfront maybe worthwhile. DAP would get used first, but as it depleted, there would be a smooth transition into Fermaid O use.


Better brewing through science!

See my brewing site at www.denardbrewing.com

See my Current Mead Making Techniques article here:
http://www.homebrewtalk.com/current-mead-making-techniques.html
 
Actually, I was trying to show that organic nitrogen is always better than dap (or at worst the same) even before the 9% point. If what I said proves your point instead I would like to know why
What you said in your post is true and it is repeated in my post, but there should be some extra information which might make organic nitrogen better than what it seems at first glance
 
This discussion has definitely gone "bio nerd." Lol. And I wish I could hang! I'm just a dumb prison guard who likes to make mead and keep it simple.

What seems to be obvious is the yeast prefer to eat dessert first, then finish up with the main course. So how do we figure out how much dessert to feed them before they go on to the steak and potatoes?
 
Actually, I was trying to show that organic nitrogen is always better than dap (or at worst the same) even before the 9% point. If what I said proves your point instead I would like to know why
What you said in your post is true and it is repeated in my post, but there should be some extra information which might make organic nitrogen better than what it seems at first glance

I think the "better" nitrogen source depends on when you are adding and what type of mead you are making. In the studies you are citing, the conditions are rather easy to deal with for the yeast (wine must). In that case, there probably isn't too much difference.

Here is where experience has to temper/challenge the published data. I know in a 1.140 SG mead, the DAP is much better than Fermaid O. I know this because the yeast produce copious amounts of fusels for Fermaid O batches that high. And that's when I I add double what everyone says to use! The yeast are too stressed out dealing with osmotic pressure to deal with processing O. That said, O is still better once you pass 9-10%.

Bottom line: Better depends on many variables. These studies tested only one variable and not in mead but wine must. No need to take it as gospel. We need more side by side experiments in MEAD to get solid conclusions here!


Better brewing through science!

See my brewing site at www.denardbrewing.com

See my Current Mead Making Techniques article here:
http://www.homebrewtalk.com/current-mead-making-techniques.html
 
This discussion has definitely gone "bio nerd." Lol. And I wish I could hang! I'm just a dumb prison guard who likes to make mead and keep it simple.

What seems to be obvious is the yeast prefer to eat dessert first, then finish up with the main course. So how do we figure out how much dessert to feed them before they go on to the steak and potatoes?

A lot of side by side testing is the only way to do this!


Better brewing through science!

See my brewing site at www.denardbrewing.com

See my Current Mead Making Techniques article here:
http://www.homebrewtalk.com/current-mead-making-techniques.html
 
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Ok ok. But the study also says that amino acids are better namely when taken early in fermentation during the growth phase and when there is no dap. But I do think we could be quoting studies all day and probably someone can bring info which contradicts this. I think Lallemand sugget dosing first with dap in highly deficient musts but I don't know if this is to avoid the nutrient addition legal limits. I wouldn't be surprised if there is a study which supports initial dap additions in meads. I also have little doubt that somehow tosna doesn't work in high gravity meads. In fact I was about to quote you on that
The thing is, I was encouraged to try to find scientific data backing claims. Through experiments we could end with different proocols such as tosna which work but we don't know exactly why. I think we coud also try asking Lallemand where exactly it was found that organic nitrogen is 3-5x more efficient as claimed in their cider handbook.
Btw there is a section which talks about amino acid intake inhibition because of alcohol toxicity. We might be overestimating yeasts' ability to use amino acids at such high levels
 
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Btw medsen, I agree that most of the arguments put forth so far do not provide conclusive evidence of this increased effectiveness, but why haven't you addressed my reference to the study you provided yourself? That study seems to show at least 3.33 times increased efficiency

I don't think I'd interpret it that way. Let's look at each of the pieces.
1.1 Trials carried out in collaboration with the INRA Pech-Rouge for the vinification of white
must
The purpose of these trials is to compare the efficacy of adding ammonium and of adding an organic nitrogen
preparation (made from inactivated yeast).
• Fermented must submitted for trial: Viognier
• Analysis of the initial content of the must:
• Sugars: 215 g/L
• Total acidity: 2.5 g H2SO4/L
• pH: 3.65
• YAN: 150 mg/L
• Turbidity: 42 uTN => addition of 0.5% of frozen Maccabeu grape solids to obtain a final turbidity of
100 uTN

Now to this white grape must that already contains 150 ppm mixed YAN they made additions of 16 ppm YAN either in the form of DAP (NH4) or in the form of Fermaid O (AA). The results show that the Fermaid O addition resulted in a fermentation that ended 70 hours sooner with less residual sugar. They did not say if this difference met statistical significance, but let's make the (BIG) assumption that it does. Does this tell us that Fermaid O is 4X more effective than DAP? Not really. It tells me that if you start with a must that has enough nitrogen to begin with, adding DAP doesn't give much benefit, but adding Fermaid O provides something that does. My suspicion is that the impact is not due to the additional AA nitrogen, but more likely it is due to other components in the autolyzed yeast including parts (cell walls) that bind yeast inhibitors (like medium chain fatty acids), or additional sterols, or additional vitamins, or other micronutrients, or some other as-yet-unidentified yeast promoter. I can't prove that at this point, but I truly doubt that a few amino acids, which are more difficult for yeast to utilize, will make much positive impact.

1.2 Trials carried out in collaboration with the INRA Pech-Rouge for the vinification of red
must
The purpose of these trials is to compare the efficacy in red winemaking of adding ammonium and of adding
organic nitrogen (from inactivated yeast) presenting identical concentrations of YAN (16 mg/L).
Fermented must submitted for trial: Portan (destemmed and crushed grapes)
Analysis of the initial content of the must:
• Sugars: 247 g/L
• Total acidity: 3.4 g H2SO4/L
• pH: 3.38
• YAN: 150 mg/L
• Turbidity: 42 uTN => addition of 0.5% of frozen Maccabeu grape solids to obtain a final turbidity of
100 uTN

This was the second test, using the same protocol, but using red grapes which were fermented and then pressed. It showed no statistically significant difference between any of the groups (the trend may suggest faster fermentation with Fermaid O). Does this tell us that Fermaid O is 4X more efficient than DAP? Positively not. In a must that has enough mixed YAN to begin with, and gets something (sterols? potassium? Mg? vitamins? etc.?) from the grape skins and pulp, the additions don't make any real difference and the nitrogen additions are equally irrelevant.

1.3 Trials carried out by the ICV in the ICV experimental winery
Another series of trials was carried out to compare the efficacy of adding the nitrogen sources described below.
C DAS: Add 22 g/hL at the one-third point of fermentation (following the protocol described by Sablayrolles et
al. 1996).
C Fermaid O: Add 40 g/hL at the one-third point of fermentation.
C Fermaid E®: Add 30 g/hL at the one-third point of fermentation.
The additions were made at the same time, which explains the considerable differences among the levels of
added YAN (Table 2).

In this trial they added Ammonium nitrogen 50 ppm, Fermaid E (mixed nitrogen 75% NH4) 42 ppm, and Fermaid O AA nitrogen 15 ppm. They added this to 3 different grape must that contained 141, 225 and 111 ppm mixed YAN respectively at the beginning. The results show the fermentation times were the same. Does this show that Fermaid O is 3X more effective because they got the same results using 1/3 of the YAN addition with Fermaid O? I'd say not. They all fermented the same regardless of additions because they probably had enough of whatever they needed to start (notice they don't show a control here) or you could postulate that all they needed for complete fermentation was 15 ppm of extra nitrogen (especially in the last batch).

Lastly, a trial carried out in an industrial situation (200 hL tanks) on a must with a high potential alcohol (15.5° v/v)
showed the positive impact on the fermentation kinetics and therefore on the fermentation activity of the yeast.
Compared to the control, receiving a mix of DAP, DAS and a yeast source at the rate of 30 g/hL at the one-third
point of fermentation, the addition of organic nitrogen helped the yeast (ICV D80® in this case) consume the sugar
under particular difficult winemaking conditions for red wines. The addition of a “classic” nitrogen nutrient in the
same Grenache Noir must, at 15.5° v/v, did not permit the completion of the fermentation. When the fermentation
stopped, the must contained 5 g/L of residual sugars.

This was the 4th example and again, really not different from what they have already shown, which to me is that Fermaid O contains nutrients that are beneficial to fermentation, and which may promote faster and more complete fermentation than ammonium additions alone. HELLO LALLEMAND - almost nobody has been adding DAP alone to mead fermentations in over a decade. We know that organic nutrients (autolyzed yeast) are beneficial which is why Fermaid K has been the "go to" nutrient for years since it combines both NH4 and autolyzed yeast.

So there is NOTHING in this article that would make me say that Fermaid O nitrogen is equivalent to 4X the amount of ammonium nitrogen. Personally I don't think it is. Nitrogen is more easily consumed by the yeast in the form of ammonium ions, but they will take up amino acid nitrogen and use it when available, and once in the cell, the nitrogen itself is used in similar fashion. The other components of amino acid metabolism may produce some better organoleptic results, but I'll leave that for a separate discussion. I have yet to see data ANYWHERE that show that yeast nitrogen requirements are reduced if the nitrogen comes from amino acids.

Where I am going with this is that I suspect it is other stuff in autolyzed yeast (which is what Fermaid O is made off) that provide most of the benefit, and I'd bet that if you could create an additive that contained all the other stuff except the amino acids, and added that to fermentations, you could probably see the same benefit while adding virtually no YAN. So, a 25 ppm AA YAN addition in the form of Fermaid O may be more beneficial to a must that already has enough nitrogen than adding 100 ppm NH4 YAN. In fact, that same 25 ppm AA YAN addition may be more beneficial than adding 500 ppm YAN with DAP*. Does that mean Fermaid O nitrogen is 20X more effective than DAP? Or does it just mean that even if yeast have enough nitrogen, there are other things they need to complete fermentation which can be found in Fermaid O (or Fermaid K, Fermaid A, Fermaid E, boiled bread yeast, etc.)?

To say that Fermaid O nitrogen is 4X more effective than DAP seems to be taking Lallemand's marketing material a bit too seriously.

Again, I’m not against Fermaid O. I love the stuff. I’ve been doing batches using nothing but Fermaid O for years. I just caution folks to be careful with the rhetoric, and try not to confuse the NewBees. It is OK to say “I think you can get successful fermentation using additions of 25 ppm AA YAN from Fermaid O” but I wouldn’t try to explain that as a “DAP equivalence.” If one feels that stating things as a DAP equivalence is necessary, let me ask this, “What is the DAP equivalence for Fermaid K?”



*p.s. It would be interesting to post up a chart showing the results of a fermentation comparison between 25 ppm YAN from Fermaid O compared to 500 ppm from DAP and then expounding that Fermaid O is really 20X more effective than DAP. You could track how efficiently a piece of misinformation gets spread and repeated in the echo chamber that is the internet (like the origin of the term "honeymoon"). That would be a fun study to publish. :)
 
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1. How big is the thing you want to fall out of solution? Generally speaking, bigger charged proteins, vitamins, etc fall out easier/faster than smaller things. Best I can tell, Fermaid O is protein chains (among other things) and will fall out much, much better than DAP, which is an extremely small molecule. As in, Fermaid O proteins will fall out and DAP probably won't unless it's very cold.

Unless the solution is supersaturated, ammonium and phosphate ions won't precipitate unless they are bound by something else.
 
Actually, all the above is what I said in the first post. I try to make it easier to understand for you guys. The information is useless if you cannot decipher it!

This also supports the idea that adding both DAP and Fermaid O upfront maybe worthwhile. DAP would get used first, but as it depleted, there would be a smooth transition into Fermaid O use.

I think this is why they created Fermaid K years ago. I have done additions of Fermaid K with all added at the beginning, and had very successful fermentations without SNA. I don't suggest that as best practice, but it can be done with good outcomes. Of course if you are adding DAP it isn't TOSNA anymore because DAP isn't organic.
 
This discussion has definitely gone "bio nerd." Lol. And I wish I could hang! I'm just a dumb prison guard who likes to make mead and keep it simple.

What seems to be obvious is the yeast prefer to eat dessert first, then finish up with the main course. So how do we figure out how much dessert to feed them before they go on to the steak and potatoes?

Don't worry, you'll be talking like a microbiologist in no time!
I think Loveofrose is right that it will take a lot of testing. Anecdotally, I can tell you that I've moved down a progression (and to hell with limits on Thiamine) from:
1) 2/3 DAP and 1/3 Fermaid K
2) 1/3 DAP and 2/3 Fermaid K
3) 100% Fermaid K
4) 100% Fermaid O

and my total YAN additions have crept up from about 150 ppm to about 250 ppm for a typical (non-high-gravity) traditional batch. With this progression I have become happier with my results. YMMV. Fortunately, being non-commercial I don't really have to worry about the additional cost.

For very high gravity batches I still use some DAP or Fermaid K because it is hard to add 400-500 ppm YAN with Fermaid O alone. Now if someone can show me that I can produce an 18% ABV mead using 100 ppm of AA YAN from Fermaid O, that's something that will make my day!
 
In each of those experiments the conclusion was that Fermaid O is better:
1. it is more efficient (At identical doses of added YAN, the preparation based on amino acids from yeast was shown to be more effective than 100% ammonium nitrogen.)
2. It produces faster consumption of sugar (a tendency towards greater efficacy in the sugar uptake emerged when nitrogen in an organic form was added for the purpose of facilitating the fermentation.)
3. You can use less of the stuff (As shown from amounts used. But I don't think this necessarily means anything with no control)
4. It facilitates fermentations of high SG musts (The addition of a “classic” nitrogen nutrient in the same Grenache Noir must, at 15.5° v/v, did not permit the completion of the fermentation. When the fermentation stopped, the must contained 5 g/L of residual sugars.)

It seems as if they were only testing for efficiency in the first experiment. Maybe the must was chosen specifically to test this, but we cannot know this. This whole study shows that Fermaid O is superior to inorganic nitrogen. Each time a study is brought forward which shows and gives a conclusion in favor of Fermaid O you're finding a caveat
So lallemand are being real Aholes and trying to sell Fermaid O as something it isn't. It is manipulating studies to show what it wants to show, not what the product actually is
EDIT: I wasn't even sarcastic in my last sentence. Maybe Lallemand are being really cheeky
 
Reading this thread is like being at one of my hospital's journal clubs, but with mead instead of diverticulitis. Mead makes for much more tasty science! :D

The point Medsen makes about the source of the article and the statistical rigor is very valid to me. It's important to keep in mind this is an industry-sponsored study, which is inherently biased. The first-author literally works directly for Lallemand. Plus, there is literally zero statistical analysis of their results to make sure they aren't the product of random chance. What I also noticed is that there are no notations on the paper about where this study was published, which makes me suspect is was released directly by Lallemand and not published in a peer-reviewed journal.

From a point of strict scientific rigor, I think the most you can conclude from this paper is that Fermaid-O is non-inferior to DAP or Fermaid-K. There simply isn't enough data or analysis to make any broader statements on sound scientific footing.

Anecdotally, I agree with Stasis. Since I started using Fermaid-O my meads have gotten way better, and I'm loving the steady fermentation kinetics compared to the boom-and-bust patterns during NH3-based SNA. In contrast to the debated study, I've seen fermentation take longer with Fermaid-O compared to DAP/Fermaid-K. There are significant confounding factors to attributing my outcomes entirely to Fermaid-O, though. For example, around the time I started using O I also started implementing much stricter temperature control.

TL;DR: Man oh man I wish UC Davis would get on all these questions we have about the comparison between O and K!

Anecdotally, I can tell you that I've moved down a progression (and to hell with limits on Thiamine) from:
1) 2/3 DAP and 1/3 Fermaid K
2) 1/3 DAP and 2/3 Fermaid K
3) 100% Fermaid K
4) 100% Fermaid O

and my total YAN additions have crept up from about 150 ppm to about 250 ppm for a typical (non-high-gravity) traditional batch. With this progression I have become happier with my results. YMMV.

So you're currently shooting for 250ppm using 100% Fermaid-O? That'd work out to be 6.25g/L Fermaid-O, right? I'm really interested in this because I focus most of my energy on traditionals.

For very high gravity batches I still use some DAP or Fermaid K because it is hard to add 400-500 ppm YAN with Fermaid O alone.

I typically make my musts in the 21-25° brix range, with the occasional short mead around 15° brix. At what point do you consider a batch to be "high gravity" and start adding additional DAP for Fermaid-K to make up the difference to the required 400-500ppm?

Now if someone can show me that I can produce an 18% ABV mead using 100 ppm of AA YAN from Fermaid O, that's something that will make my day!

I made a batch of Oskaar's Mutiny On The Bounty Cyser using TOSNA. Total Fermaid-O was 38.5g in 20L of must, to give 77ppm YAN. I suspect this doesn't count as far as day-making goes because the recipe also calls for a ton of dates and raisins. :)
 
In each of those experiments the conclusion was that Fermaid O is better:
EXACTLY! Fermaid O is better than DAP alone.
Not,"the amino acid YAN is the equivalent of 4X as much ammonium YAN."
Not, "when using amino acid YAN from Fermaid O, the yeast need less nitrogen."
Fermaid O is better. That is about all you can say, and that is the point I have been trying to make.

1. it is more efficient (At identical doses of added YAN, the preparation based on amino acids from yeast was shown to be more effective than 100% ammonium nitrogen.)
2. It produces faster consumption of sugar (a tendency towards greater efficacy in the sugar uptake emerged when nitrogen in an organic form was added for the purpose of facilitating the fermentation.)
3. You can use less of the stuff (As shown from amounts used. But I don't think this necessarily means anything with no control)
4. It facilitates fermentations of high SG musts (The addition of a “classic” nitrogen nutrient in the same Grenache Noir must, at 15.5° v/v, did not permit the completion of the fermentation. When the fermentation stopped, the must contained 5 g/L of residual sugars.)

It seems as if they were only testing for efficiency in the first experiment. Maybe the must was chosen specifically to test this, but we cannot know this. This whole study shows that Fermaid O is superior to inorganic nitrogen. Each time a study is brought forward which shows and gives a conclusion in favor of Fermaid O you're finding a caveat
So lallemand are being real Aholes and trying to sell Fermaid O as something it isn't. It is manipulating studies to show what it wants to show, not what the product actually is
EDIT: I wasn't even sarcastic in my last sentence. Maybe Lallemand are being really cheeky

I'd quibble with you on number 2. It did not show a significant difference between any of the groups.
I won't criticize Lallemand for being very effective marketers and promoters of their products, but they didn't achieve their market position by divine right. However, it is incumbent on us to try to pick through marketing hype to understand what is real, and to test things to confirm that reality to the best of our ability. Fortunately there are great places like this forum where folks can bring a lot of different perspectives and experiences to help us all develop best practices.
 
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"EXACTLY! Fermaid O is better than DAP alone."

Well not exactly dap alone. all experiments were on grape musts which contain a high amount of organic nitrogen, vitamins, etc.

I still can't imagine how tosna would work reliably in two weeks with 50ppm Fermaid K, Go ferm and yeast hulls. In my mind there still is something special about fermaid O
 
So you're currently shooting for 250ppm using 100% Fermaid-O? That'd work out to be 6.25g/L Fermaid-O, right? I'm really interested in this because I focus most of my energy on traditionals.

It depends on the yeast. If I'm using 71B, I can go lots lower (125-150 ppm) and feel comfortable.
For the usual suspects - D47, D21, K1V, cote des blancs, etc. I'll usually run between 200-250 ppm. And yes, that is 5-6 g/L. It gives you a bit of yeastiness that may need a little while to age out, but produces some very nice mead.


I typically make my musts in the 21-25° brix range, with the occasional short mead around 15° brix. At what point do you consider a batch to be "high gravity" and start adding additional DAP for Fermaid-K to make up the difference to the required 400-500ppm?

Well, to start, many folks will make 18% meads using EC-1118 and won't use anywhere near 400 ppm. You'll see people doing it with variations of Hightest's SNA protocol at 150 ppm and it can be successful. I've tried at times to get above 18% and in that circumstance, higher levels of nutrients have helped. When I go above about 14% (SG 1.105) I start increasing the nutrient levels in a more-or-less linear fashion. So it may look something like:
14% 200 ppm
15% 250 ppm
16% 300 ppm
17% 350 ppm
18% 400 ppm

I'm not necessarily that regimented, and I don't always use that much, but if I'm using a nutrient hog yeast, I'll bump things up a little. I'm not saying this is best practice, but I have found it helps me.

I made a batch of Oskaar's Mutiny On The Bounty Cyser using TOSNA. Total Fermaid-O was 38.5g in 20L of must, to give 77ppm YAN. I suspect this doesn't count as far as day-making goes because the recipe also calls for a ton of dates and raisins. :)

Cysers are a different beast. The apple juice contains a good amount of nitrogen, and something in apples (sterols maybe?) drives yeast into a frenzy and so the nitrogen needs are lower.