PDA

View Full Version : SNAs - The more I read the more confused I become



ReadMead
05-07-2014, 05:56 PM
So I've done my research. I've read the compleat meadmaker, I've joined the site and read countless threads. I'm finally feeling confident enough to shell out some hard earned money for what seems to be the true liquid gold. However, my one area of confusion still stands with SNAs. I realize this is a highly debated topic so I know what I could be in for as far as responses go, but here goes....

It seems to me that a very common ratio is found on this site (also in Ken Shramms book) of 2:1 Fermaid K to Dap, stagerred roughly every 24 hrs from the end of the lag phase until the 1/3 sugar break. In addition it seems a consensus has been reached on rehydrating your yeast with 1.25g goferm for every 1g of yeast. This all makes perfect sense to me.

Through further digging in numerous threads on this site I began coming across people mentioning the Ken Shramm Article on "Optimizing honey fermentation" in which he states a very different nutrient schedule. From the article - "...I have been utilizing staggered additions of a combination of 1gram DAP and .5g Fermaid K at pitch and at 24 hour intervals for three days. Fermentation times have been reduced, and the resulting meads have been of very high quality requiring less aging to reach drinkable maturity".

The two things that concern me with the "Optimizing Honey Strategy" are these:
1) the ratios of 2:1 Dap to fermaid K seems to be the oposite of what most people actually use.
2) I've read in many threads that adding Dap at pitch is bad for the yeast.

A lot of people have referenced this article but I rarely see the nutrient regimen used in peoples recipes.

Can anyone shed some light on this so my head stops spinning???

Cheers!


Any

Get_Wiggly
05-07-2014, 06:48 PM
So I'm in the same boat as you, I don't quite understand the actual biochemistry of it. However I once read in an abstract that "High nutrient concentrations cause higher alcohol and fusel alcohol formation" - as well as high temperatures and "agitation". However this is the only time I've read this, and often wine/beer journals aren't very scientific (cruddy science).

DAP is important for yeast at the beginning of fermentation - it supplies high quantities of nitrogen, which are required for metabolism of sugars. DAP is more important in the first half of fermentation than the later half. The reasoning behind this isn't clear to me - but with low nitrogen yeast will stall out or become very slow to ferment.

Nutrient (amino acids, etc) are what keep the yeast from becoming stressed while fermenting. Without nutrient, yeast may continue to ferment (with available nitrogen) but are more apt to produce off-flavors, such as sulphorous compounds and higher alcohols. This is because the 'energy' (energizer, DAP) is there, but the basic building blocks are not, and thus the yeast are going to use the crap thats available to them.

Think of DAP as caffeine, and nutrient as a full bodied meal. DAP is going to allow fermentation to happen quicker, and nutrient is going to allow it to happen with less stress on the yeast.

As for your original question the ratios are going to depend on the yeast used, and the must. If you have a very high OG, DAP may be required, while nutrients aren't going to be essential right away. If you have a lower OG, DAP is going to be less essential, while nutrients may be the bottle-neck of fermentation.

So here is my 2 cents, which is totally amateurish and founded on serious bias and ignorance;

DAP at the start with liquid cultures with the 2:1 that schramm specifies.
With dry yeast, don't DAP at the start, DAP 24 hours after pitch.

During fermentation - if your OG is >1.11, use 2:1 DAP:Nutrient (even with dry yeast), if its <1.11 1:2 DAP:Nutrient. I Would go so far as to say the last 1/3 break doesn't need DAP, but may require nutrient.

Feel free to completely ignore this.

Bob1016
05-07-2014, 08:26 PM
There's a lot of good info there and what I end up saying may just be really confusing, but hopefully not.
Yeast require several things to live, and all we really want is for the yeast to live and go about their business naturally, with strategic guidance.
Carbon- the true energy source for yeast is the same as most other living creatures: ATP and NADH. The yeast produce these through glycolysis (as with many other living things), which is a metabolic process by which glucose isomers are transformed into pyruvate (which is then transformed into ethanol in an attempt by the yeast to recycle some energy, which has the benefit of creating an antiseptic environment). The glucose isomers used in the initial stages of this process act as the carbon source for most yeast species, but other sources can be used by certain species of yeast.
Nitrogen- nitrogen is used through all metabolic pathways to help in the process of glycolysis and to maintain cell health. Yeasts can take up many forms of nitrogen including most amino acids (except proline) and ammonium ions (called inorganic nitrogen due to a lack of carbon in the compound/ion). Ammonium ions are a great source of N for yeast as they are easy to use and nutrient dense, but in excess they cause growth that is too rapid and cause the yeast to require even more N. It is also very hard for yeast to utilize ammonium past the 1/3 sugar break (I think lallemand quotes a 80% decrease in use, though I'm not sure if the PNR is due to abv, sugar consumed, or other factors), and as such it is advised not to add DAP in any form past the 1/3 break.
Amino acids can be directly used by the yeast in metabolic pathways or transforms red into other amino acids for use. They are responsible for the long term nutrition of yeast and can be added up to the end of fermentation, though yeast don't take up much nitrogen past the 2/3 break. Lallemand has a study that shows that 20 ppm N from ammonium added at the 1/3 break shows worse fermentation kinetics than 5ppm N from amino acids. What this means is that yeast prefer inorganic N, but organic N (amino acids and vitamins) are far better for them.
Sulfur- strange to think that this is actually something yeast need, but it is. Yeast need an amino acid that contains sulfur (can't remember the specific one) for several metabolic functions. Luckily yeast can use ionic sulfate and build this amino acid from other amino acids and sulfate.
Minerals- many minerals are needed to act as catalysts in yeast metabolism and are generally found in the water we use for honey dilution. A ratio of 25:1 potassium to hydrogen is required for health throughout fermentation, and stuck ferments can many times be traced back to an imbalance of potassium, as such potassium should be added to mead musts (and it turns out that adding it after fermentation onset cannot correct the initial deficit, so add it early). Yeast also prefer high magnesium compared to calcium (something like 2:1 if I recall), and many nutrient blends contain magnesium sulfate to huge this balance in the right direction. Zinc is needed as well, but many nutrient blends have it and when in doubt Servomyces from whitelabs is a great product.
Vitamins- I could list strange compounds here, but I'll just say that there are a few key vitamins that help prevent H2S production in yeast and every nutrient blend contains them in some form.

This is written so that you can understand the background and make a good guess at what will work.

2:1 fermaid K to DAP works, but so does 100% fermaid K, and 2:1:4 DAP:fermaid K:fermaid O also works great.

Front load on the nutrients due to decreased use as fermentation continues.
Make sure vital things are there in the begining when they need to be: potassium, vitamins, and co-factors.
Feed as often as possible.
No DAP after 1/3 break, some recipes don't follow this and it can work, but they are usually exceptions.
Organic N can be added up to 1/2-2/3 break, but keep the doses small due to lack of utilization.
Aerate often.


Sent from my Motorola DynaTAC 8000X using Tapatalk

Bob1016
05-07-2014, 08:29 PM
Hah! Tapatalk was lagging and I had to post before finishing.
I forgot to talk about oxygen and aerobic vs anaerobic fermentation, but simply put aeration forces aerobic fermentation which is less efficient, but more productive than anaerobic fermentation.
I guess that's it for now, hope I'm not making this too confusing. This really belongs on my blog, but I don't want to be "that guy" and just refer everyone there.


Sent from my Motorola DynaTAC 8000X using Tapatalk

ReadMead
05-07-2014, 11:18 PM
And that is why I love this forum after only being here for 5 days! Thanks Get_Wiggly and Bob1016 for the quick and thorough replies.

Although some of the background info from Bob1016 went over my head, I did get enough to better understand the nutirents role in the fermentation process. I've been brewing All grain beer for 3 years now and I think that little lesson will help me with my beer brewing as well.

I like the idea of having some Fermaid O in the mix and being able to use some between the 1/3 and 2/3 sugar break.

Any info you could point me towards for coming up with appropriate FAN/YANc levels using the 2:1:4 DAP:fermaid K:fermaid O regimen? I plan to do a couple BOMM recipes in the 1.090 range to get started. One with blueberries and one with blackberries, both with raw wildflower honey.

Cheers!

Bob1016
05-08-2014, 06:10 AM
For BOMM, follow the recipe exactly (concerning the SNA). This http://www.gotmead.com/forum/showthread.php/22064-2013-honey-experiment is what I was referring to with that specific ratio. Honestly I'm becoming a bigger fan of fermaid K to ~150ppm and a 1g/L dose of fermaid O at half fermentation mark.


Sent from my Motorola DynaTAC 8000X using Tapatalk

Bob1016
05-08-2014, 06:13 AM
The levels depend on yeast strain. Low N requirement generally means <200ppm (above 140ppm), med somewhere around 200-300, high being >300 ppm. Although the SG and temperature also change these ranges (as temp goes down, so does YAN requirements as long as the yeast are not a the extreme ends; as SG goes up, so does the need for N).


Sent from my Motorola DynaTAC 8000X using Tapatalk

fatbloke
05-08-2014, 06:23 AM
Well the OP should be able to see there's no "set" or correct way for this other than the recommended ppm for nitrogen.

personally I like to bias my mixes toward more fermaidK and then make the numbers up with DAP, to make sure there is enough of the non-nitrogen elements i.e. 2 FK and 1 DAP........

I can't source FermaidO here so thats out, but boiled yeast seems to work........

Get_Wiggly
05-08-2014, 04:56 PM
to be honest I eyeball everything I do.

Eventually I'll get more consistent. :)