Want to avoid brine/ umami off-flavors, especially in short meads? This article proposes taking the YAN contribution from Go-ferm into account and avoid excessive minerals by tailoring the nutrients to your water profile.
A common complaint for short meads is that they can have a briny/ umami flavor. I have lost 1 gallon short mead batches to these off-flavors when using nutrient calculators such as the Meadmakr nutrient calculators. This is also a common compliant for many who have tried to replicate public recipes of the short meads published by Groennfell or Havoc Meadery and didn’t have Wyeast Yeast Nutrient. But what makes these off-flavors more likely in short meads and in small batches?
From my experience, the umami flavor (think wet dog food/ aged cheese) is because the YAN contribution of Go-ferm rehydration nutrient is completely ignored in nutrient calculators. The Scott Labs 2016 Handbook suggests that when using a dose of 25 g/hL Go-ferm adds 7.5 mgN/L. This is three-quarters of the YAN contribution compared to Fermaid-O. However, no current calculator takes this into account! Also, the combination of Fermaid-K and Go-ferm can add quite a bit of minerals to your water profile, which combined with a high mineral profile water can potentially result in mineral off flavors.
The extent of the biases induced by Go-ferm in nutrient calculators is a larger problem in short meads and smaller batch sizes, but still exists in larger volumes and higher gravity. This article discusses biases in nutrient calculators. It also provides a recommendation for a revised best practice for nutrient regimes when using Go-ferm. I call it Tailored Additions of Nutrients with Go-ferm (TANG). Basically, the biggest takeaway is that while it is often said it is hard to over-pitch, it is possible to overpitch if using Go-ferm with the recommended rehydration protocols.
YAN Overload Example: a 5 gallon 7% ABV sparkling dry traditional mead using the default Fermaid-O / Fermaid-K / DAP nutrient protocol for a yeast with a low nutrient need from the The MeadMakr BatchBuildr. Recommended YAN is 99 as suggested in the Scott Labs Handbook. The MeadMakr Advanced Nutrient Calculator recommends 10 grams of dry yeast, and the following nutrients:
- Go-ferm: 12.5g (79.4 YAN)
- Fermaid-O: 8.5g (72 YAN)
- Fermaid-K: 5.1g (27 YAN)
In this example, you can see the total YAN addition inclusive of Go-ferm is 178.4 YAN, 80 percent more than the recommended 99 YAN. Why would this matter? Well, if you took the nutrient calculator and try to have Fermaid-O provide the extra 99 YAN, any addition of Fermaid-O above 8.5g would give you a warning that it “risks adding yeasty flavors.” Go-ferm is mostly deactivated yeast cells so such a large addition of Go-ferm with this protocol would most likely add yeasty flavors.
This example could be further compounded if one tried to follow Groennfell’s recipes and pitched with 5 grams of yeast per gallon. In such a case you would rehydrate 25 grams of yeast using 31.5 grams of Go-ferm (using 1.25 g of Go-ferm per gram of dry yeast), which would contribute 198.5 YAN from the Go-ferm alone, 200 percent the recommended YAN. It is also a bigger problem in smaller batches, due to rounding up to a full packet of yeast, see examples below.
The Pitch Rate and ABV Biases:
The below figure graphs the recommended and actual YAN contributions which include the YAN contribution from Go-ferm. The recommended YAN and Go-ferm amounts are from the The MeadMakr BatchBuildr. The meads are a 6.5% ABV dry traditional mead, and a 14% ABV traditional mead finishing at 1.01, both with a low YAN requirement yeast. The nutrient regime is the Fermaid-O / Fermaid-K / DAP which is based on Travis Blount-Elliott’s white paper, but the values do not depend on the nutrient regimes using the protocols from The MeadMakr BatchBuilder.
You can see here that the problem of high YAN is larger in smaller batches, especially for one gallon batches. At one gallon batch sizes, for the lower ABV mead, the total YAN taking into account the contribution of Go-ferm is over three times the recommended amount, and has 100 more YAN than a two gallon batch. At one gallon batch size, total YAN is twice as high for the higher ABV mead and again has 100 more YAN than a two gallon batch. This reflects two things:
- Pitch Rate Bias: introduced by not pitching a constant amount of yeast/Go-ferm per gallon (and using Go-ferm at 1.25 weight)
- ABV Bias: introduced by using the same amount of yeast/Go-ferm per ABV level
The Pitch Rate Bias is driven by not pitching a consistent amount of yeast per gallon and is what drives the downward and fluctuating total YAN by volume. The ABV Bias is driven by pitching a consistent amount of yeast for each ABV level and is what drives a constant gap between the recommended and total YAN even at high volumes of must. The total YAN is 90% higher than recommended at 12 gallons for the 6.5% ABV must, but only 40% higher than recommended at 12 gallons for the 14% ABV must. Hence, the Pitch Rate Bias is more of a problem for small batch sizes, but the ABV Bias is more of a problem for smaller ABV meads compared to higher ABV meads.
The Pitch Rate Bias does not exist for the TOSNA 2.0 regime in the MeadMakr TOSNA 2.0 Calculator, but does still exist if you use the TOSNA 2.0 regime in The MeadMakr BatchBuildr if rounding up to full packets of yeast. Lets look at the TOSNA 2.0 regime and using 2 grams of yeast per gallon to see what we get.
Note that in the figure, the recommended YAN number comes from the MeadMakr BatchBuildr (since this article has been published the calculator changed the wording of “YAN recommended” has been changed to “YAN provided”). You can clearly see that the pitch rate bias is lost – the amounts of YAN are constant for each volume of must. However, since the pitch rate is the same for both the 6.5% and 14% ABV meads, the contribution of Go-ferm adds a constant amount of YAN to the total YAN for both meads. This can be seen by comparing the total and recommended YAN in TOSNA 2.0 by ABV level.
The contribution of the YAN from the Go-ferm is a constant amount of YAN added to the YAN contributed from Fermaid-O. How different the total and recommended is by ABV can be seen from the below figure.
For a 4% ABV short mead, the total YAN is 90% higher than recommended whereas for a 11.5% ABV standard mead, the total YAN is only 30% higher than recommended.
The Pitch Rate and ABV Biases: TOSNA 3.0 (Updated April 2019)
Since this article was first published in October 2017, TOSNA 3.0 was released. TOSNA 3.0 comes with a nice new calculator but the main difference in terms of nutrients is that the pitch rate differs by OG. Let’s see what changed.
The below graph shows the YAN for two meads using TOSNA 3.0.The meads evaluated are a 6.5% ABV dry traditional mead, and a 14% ABV traditional mead finishing at 1.01, both with a low YAN requirement yeast. For the low ABV mead, the lower pitch rate means that less YAN is added from the Go-ferm and the excess total YAN from recommended drops from 71 percent to only 28 percent. The total YAN for the high ABV mead is the same, nothing changed since 2 grams per gallon is pitched for the starting gravity.
Now we compare the total and recommended YAN in TOSNA 3.0 by ABV level. Notice that relative to TOSNA 2.0 regime in The MeadMakr BatchBuildr and using 2 grams of yeast per gallon, TOSNA 3.0 has YAN provided that is closer to the recommended levels. There are three big jumps in the curve when the pitch rate adjusts.
Since the YAN contribution from the Go-ferm is no longer constant in TOSNA 3.0, the excess YAN contributed from Fermaid-O. How different the total provided and recommended by ABV can be seen from the below figure. For a 6.3% ABV dry short mead, the total YAN is 27% higher than recommended (compared to 70% in TOSNA 2.0) whereas for a 14.1% ABV dry mead, the total YAN is only 4.8% higher than recommended (compared to 25% in TOSNA 2.0).
Basically, compared to TOSNA 2.0, TOSNA 3.0 reduces its ABV bias but also introduces a pitch rate bias. The pitch rate bias is due to the gravity levels at which the pitch rate adjusts, 1.110, 1.130, and 1.160.
Severity of the Biases
Lets stop and reflect for a second on the severity of the biases.
- The pitch rate bias is the largest for one gallon batches if rounding to full packets, and is clearly inconsistent with recommendations. Not rounding to full 5 gram packets or varying the amount of yeast steadily by starting Brix can easily fix this.
- The ABV bias from not taking into account the contribution of Go-ferm by ABV is really an argument about how much YAN to add (the appropriate Recommended/Provided YAN level), and is more debatable. Slightly higher nutrients than the recommended level is probably beneficial and prudent in meads (also smaller pitch rates, more oxygen additions, higher temperatures, or anything else that increases nutrient uptake), but for short meads with high pitch rates, the additional nutrients from Go-ferm may be detectable. Moreover, nutrients are expensive and an overload can encourage spoilage. Also, you want your yeast to clean up fermentation by-products (such as acetaldehyde) and too many nutrients may make your yeast lazy, and less prone to cleaning up.
So how much extra YAN should be provided? If meads are harder to ferment than wine, maybe 10-40 percent before excess mineral off flavors are noticed. Maybe this is also because mead makers use different fermentation practice: adding the extra oxygen, degassing, etc. I have pitched meads at exactly the Scott labs handbook guidelines with a YAN of 10*Brix*Gravity*NutrientMultiplier. Most turned out fine, some of the higher gravity meads slowed down around 12-13 percent ABV (for a 14 percent semi sweet trad using 71B). Let’s look at some possible alternatives.
The 2017 Scott Labs Handbook recommendations a pitch rate of 0.95 grams/gallon up to 25 brix, 1.33 grams/gallon from 25-30 brix and 1.5 grams/gallon from 30+brix. They also say 1.9 grams/gallon for icewine. We can look at what this provides in terms of excess YAN compared to their recommended level.
We can also compare to a method that pitches yeast to pin down the desired excess nutrients. In this case the pitch rate in terms of grams per gallon can be given by the following formula.
grams/gallon=(Brix*(1+(percent excess)/100)-(YAN from Fermaid-O))/39.63
Where percent excess could be say, 20 or 40 percent. Let’s use the TOSNA 2.0/3.0 recommended amount of Fermaid-O and its YAN contribution and see what happens to pitch rates using this formula. Let’s also compare it to the Scott labs handbook pitch rate and the TOSNA 3.0 pitch rate.
As can be seen the TOSNA 3.0 and the Scott labs handbook pitch rate are the same below 25 Brix, so too is the excess nutrients. The main difference is that the Scott labs handbook pitch rate is below 10 percent excess nutrients for meads below 10 percent ABV. In contrast, maintaining a constant excess nutrients gives similar pitch rates, but falls to close to half a gram per gallon at around 8.2 Brix.
Experimeads Evidence for Go-ferm Off-flavors
Pitch Rate: 1 gram versus 5 grams per gallon. This article found that all else equal, a five gram per gallon pitch rate combined with the recommended amount of Go-ferm resulted in significant off-flavors compared to a mead with only 1 gram pitch rate with the recommended amount of Go-ferm.
Water Mineral Profile
While water mineral profiles is an important topic in making beer, it is mostly overlooked in mead making. This must change. It is important to consider that your nutrients are building a water mineral profile and that the combined minerals from your water and nutrients should be taken into account.
Go-ferm andFermaid-K have minerals in the nutrient, whereas DAP and Fermaid-O do not (although, they naturally exist in the yeast hulls in Fermaid-O). Thus, in excessive amounts Go-ferm and Fermaid-K risk adding mineral or brine character depending on the mineral profile of the water. I have used all nutrient protocols with either spring water, 50/50 spring water and distilled water, and filtered city water to make meads. I found that the spring water gave me a brine flavor (especially in short meads) and the filtered tap water did not. The table below shows the mineral profile for an example of a typical natural spring water from Kingston, Ontario, Canada:
In contrast, the Bicarbonate and Calcium levels of the Kingston, Ontario tap water are more than half of that of the spring water:
I also noticed that the spring water gave much better flocculation of the yeast compared to the filtered city water, something that I attribute to the higher calcium levels. The same nutrient additions to the above two water profiles will give very different mineral contents in the final product.
Just for fun, lets compare this to the Ozarka® Brand Natural Spring Water that Bray Denard prefers to use in his BOMM recipes.
Here I report the highest values in the 2016 water analysis. You can see that the water profile recommended for the BOMM is very light on minerals. In fact, the total dissolved minerals in the Ozarka® Brand Natural Spring Water is 20-120 ppm. This puts the water in the slight to moderate mineral content range. In contrast, the water profile of the Kingston Ontario City water is 120-140 putting it in the moderate to high mineral content range and the natural spring water that is sold in Ontario is 300 ppm, which has high mineral content.
The low mineral levels of the Ozarka® Brand Natural Spring Water may be why Bray adds potassium bi-carbinate to his meads – as there is less minerals to buffer against the PH drop compared to a higher bi-carbonate water. An interesting question: do you need to add potassium bi-carbinate (or potassium carbonate ), depending on the original carbonate levels of your water? Probably not if you have high mineral content water.
It is also notable that Sergio Moutela owner of Melovino Meadery and creator of TOSNA 2.0, uses reverse osmosis water in his mead making. While there has been little attention attached to water profiles/ building water profiles from nutrients, this is likely to be a topic explored in the future.
From my experience (and using Brays and Sergios success), when using Go-ferm or Fermaid-K you want water with lower mineral levels to avoid mineral off-flavors.
Experimeads Evidence for Mead Water Chemistry
High Chloride to Sulfate Ratio and High Mineral versus Low Mineral Content. These articles found that all else equal, for a sample size of a dozen participants, tasters were unable to significantly distinguish between a mead with a low mineral and chloride to sulfate ratio with a mead dosed post fermentation with higher mineral and chloride to sulfate ratio. However, most participants who correctly identified the odd mead out preferred the mead with higher chloride and mineral content.
Tailored Additions of Nutrients with Go-ferm (TANG 2.0) :
Tailored Additions of Nutrients with Go-ferm (TANG) is not a nutrient protocol, just a philosophy. My recommendation is to use TOSNA 3.0 and/or similar protocols, especially for ABVs above 6 percent. Just remember that when using Go-ferm and online calculators:
- Avoid the pitch rate bias by tayloring your yeast pitch to the original gravity. Don’t round up. Use TOSNA 3.0 or Scott Labs Handbook recommendations on pitch rate.
- If you deviate from these recommended pitch rates, take the YAN contribution of Go-ferm into account (especially in short meads).
- Increase the YAN requirement of the yeast in a high temp, high oxygen, or low PH environment.
- Use water with lower mineral content or watch the combined mineral content of the water and nutrients.
To calculate the YAN contribution from Go-ferm, pretend it is Fermaid-O with an effectiveness of 3 using The MeadMakr Advanced Nutrient Calculator. If the equivalent amount of Go-ferm in Fermaid-O gives a warning of adding yeasty flavors in the calculator reduce the amount of Go-ferm. If you want to do the calculations for other types of nutrients see the YAN contribution of common nutrients.
The reason I suggest the use of Go-ferm and/or Fermaid-K with Fermaid-O is because it is recommended by Scott Labs, the creator of these products. As stated in Scott Labs 2016 hand book:
“Fermaid O does not contain any DAP or supplemented micronutrients. For optimal results, Fermaid O should be used in conjunction with an appropriate yeast rehydration nutrient (GoFerm or Go-ferm Protect Evolution) to assure proper micronutrient nutrition of selected yeast from rehydration through completed fermentation.”
Hence you should use Go-ferm and/or Fermaid-K in conjunction with Fermaid-O to get some micronutrients.
Another option, as mentioned by Jeff at The Mead House Podcast when TANG was discussed on Episode 67, is to not use Go-ferm at all for low gravity meads. Osmotic stress to yeast only really kicks in at 1.104 OG or higher, so Go-ferm may not be totally necessary at lower gravity. This may work as the rehydrated yeast should already have a store of minerals and amino acids, needed for the quick fermentation of a short mead. However, I still recommend the use of Go-ferm even at low gravity. First, because Scott Labs recommends it and it is prudent. Second, I prefer to make an activated starter to ensure a quick start to fermentation and reduce the contact of nutrients with spoilage organism. This is particularly true for yeasts that have a low competitiveness factor.
What should the pitch rate be for a mead? Groennfell meadery pitches at 5 g per gallon. Ken Schramm of Schramm’s Mead pitches at 3-4 g per gallon. Michael Fairbrother of Moonlight meadery pitches at 1 g per gallon. TOSNA 3.0 varys the pitch rate from 1 to 4 grams per gallon depending on starting gravity. I usually pitch somewhere close to TOSNA 3.0 but also pitch at higher rates occasionally. But beware: there is very little validated evidence of how pitch rate interacts with recommended YAN to affect the presence of off-flavors. Over pitching may increase the risk of off-flavors since the dry yeast are already relatively well fed with nutrients.
I generally recommend following a staggered nutrient regime. Use what TOSNA 3.0 recommends if using TOSNA 3.0. If deviating I would suggest not using a hard and fast rule for timing and amounts, but rules of thumb:
- For short meads, with high pitch rates, the fermentation is done very quickly (2-5) days. In this case, add all or most (~60-75%) nutrients upfront at pitch and the remainder at 12, and 24 hours.
- For standard/ sack meads follow the gravity readings closely. Rehydrate using Go-ferm, then stagger the other nutrients for the first few days and get the last one in before 1/3 sugar break, but especially before the 1/2 sugar break and well below 8% ABV.
The reason you need to be flexible is given by the following example. I have pitched the same yeast on two 1.120 OG musts, where one had grape juice and the other had whole currents. The grape juice fermented out twice as fast as the other and passed the 1/3 sugar break by the day 2, showing signs of yeast stress (smells of rotten egg – which I fixed right away by adding Fermaid-O and degassing). You would want to pre-emptively avoid this yeast stress by adding nutrients sooner to the pyment in this case compared to the current mead.
Oxygen, Temperature, PH:
Oxygen: The more additions of oxygen will delay/restart the lag phase and increase the yeast count, and result in more nutrient absorption. Make sure to stagger nutrients to insure that there is plenty of YAN/ micronutrients for the lag phases induced by the oxygen additions. From Scott Labs 2017 Handbook page 36: “When adding more oxygen to the must/juice, nitrogen is captured faster and more is needed when compared to fermentations taking place under anaerobic conditions.”
Temperature: The warmer the temperature, the faster the lag phase and fermentation so you may want to get your nutrients in sooner to ensure that there is plenty of YAN/ micronutrients. From Scott Labs 2017 Handbook page 36: “An increase in temperature stimulates the growth of yeast and fermentation rate, thereby requiring increased levels of nitrogen.”
PH: The lower the PH, the more stress of the yeast and the harder it can be for the yeast to absorb nutrients. From Scott Labs 2017 Handbook page 36: “At pH 3 only 70% of ammonia can be utilized compared with > 90% at pH 4. This can modify the handling of acidic whites or high pH reds.”
Oxygen, Temperature, PH YAN Multipliers: Ideally, we would have a multiplier formula just like Scott Labs have for the yeast requirement multiplier. Let’s look at the yeast multipliers.
- For Low N requiring strains: 0.75
- For Medium N requiring strains: 0.90
- For High N requiring strains: 1.25
Going from a Low N to a Medium N requirement and a Medium N to High N requirement represents a 20 and 33 percent increase in the total recommended YAN. This range may be useful a benchmark excess multipliers for how to increase the nutrients/pitch rates in a high oxygen, high temperature, or low PH environments.
TANG example 1: Nutrients for a 5 gallon batch of my 8 % ABV lemon basil mead with scored 40/50 and 45/50 in the Winnipeg 2017 Pro/ Am Brew Challenge. Recommended YAN is 112.5 as suggested in the Scott Labs Handbook. The MeadMakr BatchBuildr gives the following:
- 10 g yeast
- Go-ferm: 12.5g (80 YAN)
- Fermaid-O: 8.5g (72 YAN)
- Fermaid-K: 7.7g (40.5 YAN)
- Total actual YAN: 192.5
TANG (here I use DAP because of the use of high mineral content spring water)
- 10 g yeast
- Go-ferm: 8.5 g (Contributed 58 YAN)
- Fermaid-K: 3 g (Contributed 16 YAN)
- DAP: 3.8 g (Contributed 41 YAN)
- Total actual YAN: 112.5
In this case you can see how the rehydration in Go-ferm would have resulted in excessive YAN additions using the The MeadMakr BatchBuildr. Taking this into account and tailoring nutrients to the water profile by using DAP to not add more minerals earned me silver and a 45/50 score for a bottle conditioned bone-dry short mead.
- Go-ferm: 6.25g (200 YAN)
- Fermaid-O: 1.7g (72 YAN)
- Fermaid-K: 0.76g (20.2 YAN)
- Total actual YAN: 292.2
TANG (here I have water with low minearl content so use Go-ferm and Fermaid-K)
- Go-ferm: 1.65 g (52.2 YAN)
- Fermaid-K: 1.5 grams (40 YAN)
- Total actual YAN: 92.2 YAN
In this case you can see how the problem of YAN provided by Go-ferm is exaggerated in lower batch sizes. Taking this into account and tailoring my nutrients reduces the risk of off-flavors.
TANG example 3: nutrients for a 5 gallon batch of 6.9 % ABV mead from Groennfell Meadery. I have made several of the recipes following the guidelines put forth in “How we brew everything we brew.” This includes fermenting at high temps, pitching 25 grams of D-47, and putting all nutrients in at pitch. All the meads turned out great using TANG. I always use water with a low mineral profile from a low mineral profile spring water or a higher mineral spring water diluted with distilled water with only Go-ferm and Fermaid-K. Recommended YAN by Scott Labs Handbook is 99 YAN. The MeadMakr BatchBuildr with your own hih pitch rate would give you the following:
- Go-ferm: 31.25g (198 YAN) – assuming you use Scott Labs Guidelines of 1.25g/g yeast
- Fermaid-O: 8.5g (72 YAN)
- Fermaid-K: 5.1g (27 YAN)
- Total actual YAN: 297
TANG (here I have low mineral content water so use Fermaid-K)
- Go-ferm: 8.5 g (54 YAN)
- Fermaid-K: 8.5 grams (45 YAN)
- Fermaid-O: 8.5g (72 YAN)
- Total actual YAN: 171 YAN
In this case you can see how high pitch rates and the use of Go-ferm can triple the actual YAN additions. Taking this into account and tailoring nutrients reduces the risk of off-flavors.
TANG example 4 (TOSNA 3.0): nutrients for a 3 gallon batch of 12 % ABV (1.09 SG) traditional dry mead using a yeast with a low nutrient requirement. 162 YAN is recommended by the Scott Labs Handbook. Note, if you select the Fermaid-O (TOSNA 2.0) regime in the MeadMakr BatchBuildr you get a different recommendation than the TOSNA 3.0. Lets review both.
The MeadMakr BatchBuildr for low nutrient yeast, Fermaid-O/ TOSNA 2.0, with 10 grams of yeast and the following nutrients:
- Go-ferm: 12.5g (132 YAN)
- Fermaid-O: 9.7g (137 YAN)
- Total actual YAN: 269
- Go-ferm: 3.8g (40 YAN)
- Fermaid-O: 9.7g (137 YAN)
- Total actual YAN: 177
In this case you can see that the overall YAN is highest for The MeadMakr BatchBuildr but still high for TOSNA 3.0. I recommend staying with TOSNA 3.0 exactly at the recommended pitch rates for higher ABV meads.
It seems that some calculators use the 1.25 grams of Go-ferm per gram of yeast pitched as a hard and fast rule. You either use Go-ferm or you don’t. However, why would some calculators ignore the YAN and mineral contribution from Go-ferm? If you want to avoid brine/mineral off flavors and help the yeast clean up any extra off-flavors (like acetaldehyde) you may want to keep the following tips TANG in mind:
- Avoid the pitch rate bias by tayloring your yeast pitch to the original gravity.
- Take the YAN contribution of Go-ferm into account (especially in short meads).
- Increase the YAN requirement of the yeast in a high temp, high oxygen, or low PH environment.
- Use low mineral content water or watch the combined mineral content of the water and nutrients.
There is undoubtedly a range of YAN that is a safe zone around the recommended YAN, conditional on your process, that ensures yeast health and reduces the risk of off-flavors. Keep in mind that even though you may not be noticing mineral and yeast off flavors, other off-flavors may not be as readily cleaned up.
This article shows some biases in calculators, but undoubtedly more research is needed. More research is needed to answer the following questions.
- What are the nutrient taste thresholds for the different regimes by ABV levels?
- What are the taste thresholds of water mineral profiles for different ABV levels?
- YAN multipliers for the pitch rate, oxygen, and temperature ranges ?
This deserves full-blown experiments. Experimeads are currently in progress so stay tuned. The TANG protocal is currently a philosophy rather than a complete protocal. Use TOSNA 3.0, but if you deviate from the protocal, keep TANG in mind.
The following are used in the above calculations:
- Scott labs handbook recommended YAN: 10*Brix*Gravity*NutrientMultiplier.
- DAP 1g/L = 210 YAN
- FERM K 1g/L = 100 YAN
- FERM O 1g/L = 40 YAN (Effectiveness multiplier of 4 so 160 mgN/g/L equivalent.)
- Go-Ferm 1g/L = 30 YAN (Effectiveness multiplier of 4 so 120 mgN/g/L equivalent.)