Yeast and addition of nutrients

[rtalbigr]

Been doin' some research on yeasts and came across this:

Yeast do respond better to staged additions over the first 1/3 of the fermentation. All the nutrients added at the beginning will result in a high level of yeast cells with each cell having a low protein content. The fermentation will be vigorous in the beginning then fizzle out towards the end. Staged additions will result is a lower cell population with high protein. This will produce a steady vigorous fermentation up to the very end. The high protein content in each cell will protect the cell from alcohol toxicity near the end of the fermentation. Staged or incremental additions of nutrients, namely nitrogen, will also minimize the production of H2S.

Found this at a Lalvin site. Specifically it was in reference to the addition of nutrients for a honey must. However, further researching I also found a similiar reference for wines.

Lalvin produces yeast nutrient called Fermaid K primarily for

"grape musts, juice from concentrate, fruit musts, corn syrup, and honey."

The direction say,

"For normal winemaking applications, the recommended addition rate of Fermaid K is 5 gm/20 L. For optimal results, 2.5 gm of the Fermaid K should be suspended in the 20 L of must just after adding your yeast culture to the must, then add the balance of 2.5 gm of Fermaid K anytime between 1/3 and 1/2 way through the fermentation."

This really resonated with my experience in fermenting. I have always added all the yeast nutrients and then pitched my yeast. After 2-3 hours (usually) they will really take off and go for about 12-16 hours and then sort of peter out, bubbling every few seconds for several days, usually finishing w/in 5-7 days.

Yesterday I started three 5 gal ferments. 1 of 1 gal mollasses w/4 gal water using EC - 1118, starting SG of 1.085. 2 of all barley wash starting SG 1.068, using 5 teaspoon Crosby&Baker distillers yeast. The molasses and one barley started as usual but the other barley was so violent that after hour 3 I pulled out the airlock and let it run for about four hours before replacing. It was still bubbling like a machinegun! Presently, about 36 hrs later, the molasses is bubbling consistently at 1 bubble/sec whereas both barleys are bubbling at about 1 bubble/3-4 sec.

All of my ferments have finished out dry but I am now wondering if I would actually get a better product but adding my nutrients in stages as recommended for honey and wines. Yeats is yeast and what's the difference whether it's fermenting grain sugars?

My next ferments will get 1/2 nutrients when pitching yeast w/the balance at day 2-3 and I'll see if there is a difference in how the ferment goes.

Big R

[Prairiepiss]

Big R in reading your post I thought about your plan. I would assume if normally you add x amount at the start and it falls short. By adding 1/2 of x at the start and 1/2 of x latter. you are still only putting the same amount in so wouldn't you get the same outcome? wouldn't you need to add x amount plus more to carry it further? Say 3/4 of x at start and another 3/4 of x later. So you would be adding an extra 1/2 of x?

[The Baker]

Interesting. I had assumed that as the yeast multiplied it would be quite superfluous to add more later.
But this is from the experts...

Maybe the yeast colony loses some...
(I thought of saying virility but that is wrong because that is about reproduction and the yeast is past the reproductive stage when the second lot is added. Or is it? I'm afraid to refer to the other postings while writing this because I will probably lose this and have to start again..)

maybe it loses some efficiency (?) (strength/ vigour...) as it goes through its alcohol producing phase and the addition of some vigorous new yeast gives it a boost.

Ignoring the first addition of yeast for the moment; would it be advantageous to make the second charge of yeast into a starter, adding a little of the wash after it got going and stirring hard to incorporate oxygen near the end of the starting time...?
This would counteract to a degree the lack of oxygenation in the wash at this stage; and maybe you should re-oxygenate the wash anyway, vigorously but not over a very long period??

[Dnderhead]

If I remember right,this depends on nutrients used,DAP,is one that should not be added
at start,it can prevent yeast from multiplying and is toxic at rehydration.(ammonia)
natural nutrients can be used at start.(like yeast halls)

[rtalbigr]

I read a study about a week ago where some scientists had been studying the origins of yeasts. Yeast is genetically wired to overwhelm its environment, destroying any other organism that it competes with. It does this by producing ethanol and by its ability to rapidly grow its population. By controling/staging the addition of yeast nutrients you are helping to limit population growth in order to get a healthier population. The resulting population of yeast will have higher protien content and higher alchol tolerance and will give a more complete ferment with higher attenuation. As Dndr states nitrogen in whatever form should be staged which will help reduce levels of H2S. Yeast also benefits from subsequent additions of yeast hulls which provides lipid which is necessary for cell division. The goal is to produce "healthy " yeast. Addition of nurtients in quantities greater than the yeast actual needs will defeat that goal.

I still have a lot to learn about this and need to find some info about the transition from aerobic to non-aerobic and how this affects growth and alchol production.

Another thing I have been pondering is the quantity of yeast that is used. EC 1118 comes in 5 gm packets (about 1 teaspoon) that is sufficient for fermenting 5 gal. Yet I have read that many people and adding up to 1/4 cup of bakers yeast for a 5 gal ferment. I use a lot of Crosby&Baker distillers yeast. When I first started distilling I asked the brew shop guy and he said 3 tablespoons. Well, I'm down to using 5 teaspoons and am thinking thats still more yeast than is actually needed. I'm thinking 1 teaspoon in a starter should be sufficient.

I have a lot more research to do about this but the way I'm thinking is that the goal should be an even, steady ferment instead of one where there is excessive action at the front end and then very weak action for several days to complete the ferment. I think that will produce a better product reducing any chance of off flavors and also a better flavor profile from what ever mash is being used.

Big R

[rtalbigr]

Since Tuesday I've read about a hundred pages on yeast. It seems yeast is one of the most studied organisms because of it mechanism of growth. In trying to apply what I've read to the addition of nutrients I've found there are a number of factors involved.

First of all, 5 gms (approx. 1 teaspoon) of most active yeast contains 150 million cells. In a proper environment a yeast colony will double in size approximately every four hours for 24-48 hrs depending on oxygen availability and nutrient availability. Proper nutrients are most important in the aerobic stage because this is when the colony growth occurs. Over abundance of nutrients accelerates growth but the result is larger numbers but weaker cells. While there is a long list of desirable nutrients the most important appear to be nitrogen in a usable form such as DAP or urea, Vit B1, lipids (yeast hulls), and a sufficient supply of O2. It is during this period that staging nutrients is important to get a healthy colony started and then to sustain growth as the colony grows. During the aerobic phase no alchol is being produced. The yeast metabolize the available sugars and the resulting products are simpler sugars and CO2.

When all the O2 is depeleted the yeast switch to the anaerobic conditions. This is when actual fermentation of the sugars to alchol begins. Colony growth stops. Gas production is significantly reduced. Nutrients are no longer an important consideration. The significant factor now is the health of the colony. A healthy colony will have better alchol tolerance and better attenuation, and the result wil be a more complete ferment.

I know this is a simple explanation but organic chemistry and micro biology was always way over my head. But researching this has given me a much better understanding of the fermentation process and hopefully will help me achieve a better product.

Big R

[rad14701]

rtalbigr, it sounds like you've been doing a thorough crash course in yeast... Too bad we can't make that a requirement here...

You are correct in that nitrogen, B vitamins, and oxygen are major considerations... And having them available for immediate uptake is imperative for timely yeast colony growth...

The only alternative to time and adequate nutrients is to over-pitch, especially if shorter fermentation times are desired... The downside to over-pitching is that once the colony has depleted all of the sugars the wash should be racked off the trub, and may even require secondary racking, in order to avoid problems due to autolysis or high %ABV of the wash causing breakdowns within both live and dead yeast...

Yeast are not as simple as one might expect single cell organisms to be...

[rtalbigr]

Rad - Over pitching is what really got me looking into this, more than anything. In researching for a yeast for mead I came across a lot of other stuff and it kinda steam rolled. I found out I have pretty much been over pitching most of what I ferment and have pretty much decided that over pitching is not the best way to go, regardless of other considerations. Over pitching and excessive amounts of nutrients establishes a very large colony but one that is less than healthy. Pitching proper amounts of yeast and using a controlled and staged addition of nutrients results in a much healthier yeast colony. The possibility of off tastes and undesirable by-products is greatly reduced or even eliminated and one will have a better final product. Isn't that actually our goal, the best product?

Big R

Edit: Ya, yeasts are some complicated little buggers!

[rtalbigr]

On further investigation I found this from whitelabs.com

Is over pitching of yeast harmful?

"If the beer is over pitched, yeast do not grow through a complete growth cycle. This results in few new cells, which makes for unhealthy yeast and low viability by the end of the fermentation."

This can have a significant effect on flavors because the growth cycle of the yeast isn't complete. Esters, phenols, fusil oils, and other flavors may not be produced thus adversly affecting the flavor profile of the wash and hense of the distillate.

Big R