Zinc Sulfate Monohydrate

There is a product called Zinc Sulfate Monohydrate that is composed of:

minimum 35.5% zinc
...and
max 10mg/kg arsenic (.001%)
max 2000mg/kg iron (.2%)
max 20mg/kg lead (.002%)

Is this a good product for brewing yeast health?

Malt itself supplies enough of all the co-factors needed by yeast enzymes with the exception of zinc so brewers often supplement it. When it comes to chemical additives I say if its food (FCC) or pharmaceutical (USP) grade and you know what you are doing then go ahead. A more practical solution for a home brewer who wants to supplement zinc is to buy one of the yeast nutrients that are sold by HBS's. They usually contain some zinc plus urea, DAP, yeast hulls... i.e. other things yeast like.

Hey thanks for responding to this. I was about to bump it. It's better than no response at all but you are essentially evading the question. Everything you said is sound and I agree with it--that is why I am posting the question. Maybe I should ask chemists or yeast specialists.

I can flip your answer around and ask you if the diammonium phosphate I buy from my brewshop is also safe if there is no 'food grade' warning. How would anyone know? Is the Wyeast yeast nutrient 'food safe'? What is the criteria? Are there trace amounts of lead in it that are so insignificant they are still food safe?

Both diammonium phosphate and zinc sulfate are used as plant fertilizers usually.

Perhaps you should.

Whether the DAP in a particular yeast supplement is safe for human consumption or not is unknown. It may be true than consumption of DAP in humans on a regular and ongoing basis over an extended period of time doubles the probability of siring a child with a second head from something like 1E-15 to 2E-15 but no one knows and no one is going to do a study to determine that because it is not doable. What you do know when you buy something like yeast nutrient or brewing salts or lactic acid or phosphoric acid from you LHBS is that they are FCC (or USP) because they can't be sold for human consumption if they are not. The FCC grading implies a certain level of freedom from things like heavy metals. Look in a chemical catalog at something like lye which is made with mercury. You may well find that there is no more mercury in ACS grade than FCC or USP grade. In all cases the heavy metal content is low. I'd give a specific example here but I go north for the summer and the brewing library stays south. So while grades fit for human consumption are low in heavy metals there is more to the story than just the purity. Handling and packaging are also considered very important. They must be carried out in a facility inspected and approved for handing and packaging things going down a human gullet. This is to insure that you don't get Campylobacter or something similar along with your zinc sulfate.

If you buy ACS, FCC or UPS grade zinc sulfate you should get an analysis either on the side of the container or on paperwork shipped with the material. From that you can see just how much arsensic, lead, mercury etc. you would get in a gram of the stuff and figure out how much would be in the fraction of a gram you would add as yeast nutrient. You could then make a decision as to whether you are willing to expose yourself to the calculated levels of those substances. Or you could, as I suggested above, look in a Fischer or Spectrum chemical catalog at the relative levels of those metals in the various grades and see if you are willing to accept exposure to whatever levels are in the ACS grade and use that reasoning that you don't care whether the stuff has been packaged on a machine inspected by the FDA because you are going to put the zinc sulfate in boiling wort which will kill any pathenogenic organisms that may be riding along. But I would never, ever recommend you do that in writing in a public space. Quite the contrary, I recommend that you only use such chemicals in FCC or USP grade if you buy them from a chemical supplier or just buy them from your LHBS or supermarket or drugstore.

That contaminant level is fine, but unless you have a scale that is accurate to 0.01g or better it will be hard to use. The concentration of zinc that is beneficial for beer fermentation is something like 5-10 micromolar, so for a 5 gallon batch you are talking about around 20mg.

There's a simple workaround for that. Dissolve 1 gram in enough water to make 100 mL of solution. Each mL of the solution then contains 10 mg.

AJ's recommendation to create a mineralized solution of known strength is a great way to resolve the addition of small mineral amounts to brewing liquor. This works with most minerals, but is most suited to those that are highly soluble. Pickling lime is one of those minerals that is typically needed only in minute amount, so a solution is a good way to go. Volumetric measurement of liquids is reasonably accurate, as is mass measurement of solids. But volumetric measurement of powdered or granular solids is less accurate.

::smacks forehead::

That's what I get for posting on HBT after taking a few too many "analytical samples" of my Belgian quad. I used all my available brainpower calculating how much ZnSO4.H2O you'd need for 5 gallons.

Kai did an experiment with zinc. I think a zinc deficiency will only be a problem after several repitches. My water has traces of zinc. I have gone over 10 generations without problems. I never have used any yeast nutrients.
http://braukaiser.com/blog/blog/2012/06/22/the-effect-of-zinc-on-fermentation-performance/

Traces of zinc in water generally mean that zinc containing brass somewhere in the system (usually a well pump) is corroding. The problem with this was that the brass also contained lead. Regulations were promulgated prohibiting the use of lead containing brass in well pumps but if you have and old pump you might want to look into this.

It's in the city water report for the mountain spring that is the primary part of my water. My water is a blend of five sources. The actual blend could change throughout the year.

I wonder how useful it would be to use a penny in the kettle to supply zinc. Pennies are primarily made out of zinc with a little bit of copper. What worries me is what else might be in there.

My purposes with zinc are in the scope of providing a single cell colony to a 5 gallon batch fermentation. The goal is using zinc for starters to create healthy cells (hopefully). I don't mind taking yeast to another brew fermentation to another but I think it would get itchy after the third. I have a very uncontrolled fermenting environment though I have a controlled yeast on slant environment.

At the risk of being repetitive: why don't you just use one of the pre-prepared formulations put up for exactly the purpose you have in mind? I'm guessing that the people at Wyeast, for example, have a fairly good idea as to how to formulate a yeast nutrient and they probably use what they sell externally or something very similar to it in their own yeast production.