Nutrient additions after the 1/3 sugar break

d.j.patterson said:

Ok, what I thought was one question ended up being several. I have searched the forums and just can't seem to find a definitive answer to these questions.

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That's probably because there really isn't a definitive answer, but I'll share a few thoughts.

As yeast go through their fermentation cycle, late in the fermentation (after the 1/2 way point typically) the yeast's ability to take up and utilize ammonium ions rapidly drops. This means that DAP (diammonium phosphate) and nutrients that contain a lot of DAP (like Fermaid K) are much less useful late in the game. This does not mean that there are no cells left that can use ammonium, just that more and more will be unable to do so. That leftover ammonium may be great food for spoilage organisms later.

Late in the fermentation the yeast can still take up nutrients in the form of amino acids, and there are nutrients that provide this without DAP. Fermaid 2133 is such a product, and yeast extract may also be useful. There are a couple of recipes that Oskaar has that specifically call for Fermaid 2133. GoFerm is a rehydration nutrient that contains a similar amount of nitrogen, along with some vitamins and minerals. It is not designed as a late addition nutrient, but I have used it in that capacity on a number of occasions and things have turned out okay, but I am definitely not following the manufacturer's guidelines.

Boiled yeast (whether wine, bread or brewers) can provide similar nitrogen amounts (perhaps a bit more) and can be used in place of a commercial product. It includes the yeast hulls .

Yeast hulls are not technically a nutrient, but they do contain some nitrogen that is assimilable and may be the base for several of these commercial products. They are particularly helpful for slow or stuck fermentations because they can bind yeast toxins like medium chain fatty acids. This can sometimes help a slow fermentation to get finished.

When a fermentation is stuck due to lack of nutrients, adding nutrients often fails to unstick it. This is one of the most common mistakes folks make - not recognizing that by the time a deficiency makes itself apparent (for aeration, nitrogen, vitamins, potassium, etc.) it is too late to add it. You have to try to make sure you meet all the yeast's needs in advance, and thus give what is needed early. This is why things are pushed to the first 1/3 of fermentation.

I hope that answers at least some of your questions.

Medsen

Semi-related question: For yeasthulls, does it make a difference if they are boiled fresh yeast, boiled bottom sediment from an old batch, or commercially bought?

Good question.

I don't know.

With commercial yeast hulls, you are just getting the cell walls. I can't say which is better. I've used the commercial yeast hulls, and I've boiled new yeast (both turned out okay), but I've not tried using boiled lees.

When boiling old lees, I am not sure if there might be some sulfur odors or other funky flavors that could potentially come through. In these cases you are giving more than just the hulls; the innards of the yeast come as well. It may work just fine, but I haven't done it. If anyone has, please chime in.

I've never used boiled yeast lees, either. I've always assumed that if there are any yeast toxins in the must, then at least some of them have been taken up by those cells that are dead on the bottom of my fermenter, and better to leave those dead undisturbed.

However I was reading (but I can't now remember where) that some off flavors may be attenuated by the addition of yeast lees that have been removed from an active fermentation, boiled, and then added back during secondary fermentation. They act to absorb sulphide-based chemicals, if memory serves....

wayneb said:

However I was reading (but I can't now remember where) that some off flavors may be attenuated by the addition of yeast lees that have been removed from an active fermentation, boiled, and then added back during secondary fermentation. They act to absorb sulphide-based chemicals, if memory serves....

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Recycling lees from the very same fermentation, I like that idea...

I have used the old lees from a stinky batch to treat sulfur odors. They were aerated and returned, but not boiled. The details are in the Big Old Blackie brewlog in the Patron's area. I'm not sure how boiling would affect things.

I have not read about this for many years, so this is old tribal knowledge that may be totally off. Take it for the value you paid for it!

When yeast dehydrates, it creates the shell that contains the nutrients needed for quick growth when in the presence of water again. However, when yeast dies in water (as in the lees of your fermenter) that same action does not happen. So, using moist left over yeast might not give the same vitamins and minerals that you would get from the hulls.

That is what I learned back when stone tablets were being used instead of the internet.

Pure yeast hulls do not provide vitamins, minerals or significant amounts of nitrogen nutrients. Yeast hulls are the cell walls of dead yeast and do contain sterols, which the yeast can use for strengthening their own membranes, along with polysaccharides and some attached protein enzymes.

Boiled or autolyzed yeast have the other nutritional elements including YAN.

This article in Wine Business Monthly may be worth reading.

Oxidized lipids (like those found in yeast lees that have been aerated or treated to boiling in an oxygen rich environment - i.e. in open air) have been shown to bind reduced sulphur compounds (such as sulphides and mercaptans) and will precipitate out and thus reduce sulphide smells in your mead. That is the only mechanism I'm aware of whereby yeast components play an active role in removing sulphur stink. The other ingredients from lees or from boiled ADY areuseful for providing late-stage fermentation nutrients, not for removing sulphides.

That was a great link! It makes good sense too. I could delete my post, but I'll leave it there with this retraction below it.

d.j.patterson said:

Thanks for the article link Medsen.

So it appears that there are three different camps on this one:

1. The reuse of lees (boiled or unboiled)
2. Commercial yeast hulls
3. Boiled active dry yeast (hulls and innards)

Fermaid 2133 states on the Scott Lab's site that it is comprised of pure autolyzed, spray dried yeast and yeast hulls. According to the article above autolyzed yeast provide more nutrient, but yeast hulls provide sterol and absorb some yeast autotoxins.

Would one work better than the others for a sulfur smell? How about a slow to finish fermentation? Or is it really the combination of the two that would appear to be the majic bullet?

Please, discuss!

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Actually, #1 on your list there is used as a treatment for sulphur smells post-fermentation, it is not used as a nutrient for the yeast.

Also, I'd add a #4 that you missed, which is the use of nutrients like goferm or fermaid 2133.