Denard Brewing

Better brewing through science.

Fermaid O Liquid Yeast Nutrient Schedule

TOSNA is a wonderful nutrient protocol that produces tasty mead (see It begins by using GoFerm to hydrate dry yeast, followed by a Staggered Nutrient Addition (SNA) of Fermaid O based on time. Amounts of Fermaid O are based on calculations of YAN in proportion to starting gravity. The end result is a clean mead with improved body and honey character over other nutrients types.

Unfortunately, I've had mixed results using TOSNA with liquid yeast. We are always worried about free nitrogen content, but tend to forget trace minerals and vitamins. I believe the liquid yeast variability is due to the lack of GoFerm to add trace vitamins, lipids, and minerals; however, adding GoFerm to liquid yeasts doesn't make sense because the yeasts are already hydrated. Fermaid K also provides trace minerals, lipids, and vitamins and is designed for rehydrated yeast. So here I suggest the addition of Fermaid K to supplement Fermaid O.

Below, I am mapping out my proposal for a liquid yeast nutrient protocol heavily based on Fermaid O. You can come up with an interesting name for it. I’ll stick to the science.

Calculated Logic

I want this protocol to be useful for home and commercial mead makers. As a result, it must adhere to the Fermaid K legal requirements (regardless of how stupid they are). See points below:

>Fermaid K = 100 YAN per g/L

>However 0.5 g/L is legal limit for commercial purposes (See Fermaid K section below). This is 1.89 grams per gallon maximum which adds 50 YAN total.

>For any gravity, add 1.89 gram Fermaid K per gallon so commercial application is possible.

>Add upfront to avoid unused DAP in the finished mead and to have trace minerals, lipids, and vitamins available at all times.

>The 50 YAN from Fermaid K is subtracted from total required YAN.

YAN by Gravity Addition

We now know yeast have different YAN requirements for different gravities. For frugality and avoidance of "nutrient off flavor" we want to add only what the yeast require. This chart is based on TOSNA/Lallemand data.




Fermaid O (grams)

Split by 3 (grams)

Split by 3 (tsp)

Wyeast 1388 Additions







All upfront, tested







Upfront, 1.076, 1.046







Upfront, 1.081, 1.041







Upfront, 1.090, 1.050







Upfront, 1.101, 1.061







Upfront, 1.112, 1.072







Upfront, 1.122, 1.082

>Add 1.89 grams Fermaid K per gallon upfront only for all gravities.

>Add 2.075 grams (1/4 tsp) potassium carbonate per gallon upfront only for pH buffering.

>Measurement with a gram scale is prefered due to the varied weight of powders.

>These are “perfect” calculations. In the real world, most will not measure to three decimal places. Just get the measurement as close as you can with your equipment.

Nutrient Addition Timing

I've never liked adding nutrients based on time. Don't get me wrong - it can work when everything is going well. But sometimes things don't go well. In addition, it doesn't seem very scientific. I prefer to add by gravity, but Fermaid O requires some adaptation from other nutrients. Since Fermaid O requires yeast to proteolytically process amino acids for YAN, I suggest adding it before the yeasts need it. I subtract 10 points from the normal 1/3 sugar breaks for my additions.

Recap of the Protocol

Step 1. For any gravity, add 1.89 grams of Fermaid K and 2.075 grams potassium carbonate per gallon upfront only.

Step 2a. For gravities below 1.100, add all Fermaid O upfront.


Step 2b. For gravities at 1.100 or above, add Fermaid O upfront and at 1/3 sugar breaks minus 10 points (upfront, -30, & -70 for 1.120 and above).

Clear as mud? See the chart for a cheat sheet.


Fermaid K

Fermaid K is a formula of yeast hulls, trace nutrients, vitamins, and DAP each added in exact quantity. Yeast proteins and DAP are the nitrogen sources in Fermaid K. DAP is like candy because it's ready to use quickly while yeast proteins are a slow sustained source of nitrogen. DAP must be transported across the membrane of yeast cells. After 9% ABV some data suggest DAP has difficulty transporting across the yeast membrane leading to DAP off flavors in the mead. It's unclear if this is all yeast or just the tested wine yeast.

Side note: Fermaid K has low nitrogen content which is why mead makers generally add additional DAP to supplement. Another problem is a federally regulated limit of use in commercial applications due to thiamine content (1.89 grams per gallon). The original BOMM SNA exceeds this limit, but no worries. Thiamine is Vitamin B1. I have not a clue why they are worried about high amounts of Vitamin B1 when my smoothie has 1000% of Daily Value. There is no report of adverse effects of high doses of thiamine. I don’t understand the reasoning.

Fermaid O

Fermaid O is yeast force fed with copious amounts of nutrients, lysed, purified for nutrient rich fractions, and lyophilized. The free nitrogen originates from the yeast proteins rather than DAP. As a result, your yeast must digest the protein to extract the nitrogen. No fermentation spikes because they can only eat so fast. The downside is that there is a lag between adding the nutrients and it being useable. This processing time is why I've decided to add the nutrients ahead of the normal sugar breaks.

YAN Contribution

Fermaid K - 100 YAN per gram/Liter; 0.5 g/L is the legal limit for commercial applications or 50 YAN.

Fermaid O - 40 YAN per gram/Liter; however, we are told the biological effectiveness is 4x what the YAN states. This gives us 160 g/L or 42.33 g/gallon YAN equivalent. Note: TOSNA 2.0 states the effectiveness is ~50 YAN gram/gallon. I'm sticking to the science, but that does make quick calculations easier!  

Gram to Volume Unit Conversions

Fermaid K = 3.6-4.8 grams per tsp depending on moisture content and packing.

Fermaid O = 2.5-4.5 grams per tsp depending on moisture content and packing.

Potassium carbonate = 8.3 grams per tsp; Always add 2.075 grams (1/4 tsp) per gallon for pH buffering.

DAP = 4 grams per tsp.

by denardb on Feb. 21, 2017, 6:47 p.m.