Adding Zinc

Happy Friday All,

So I've been reading the new yeast book and it states that the only nutrients wort does not have for fermentation/yeast health are oxygen and zinc. Obviously most of us add oxygen in one form or another but how many actually add zinc and if you do, what form do you use? Can I just grind up a zinc vitamin and add it to the boil? How much would I add? Say per 5 gallons?

If you're yeast have been doing fine without it before now, I'd say skip it. Who knows what kind of unintended effect it might have?

Well sure, I've made over 60 batches without it but when Chris White and Jamil say something I tend to listen. Does anyone know if Servomyces contains zinc?

Are you sure you read it right?

Everything I've read (admittedly not much) says there is enough zinc extracted from the brewing process for proper yeast growth, and this is what we find in all of our processes (i.e. I don't add zinc, you don't add zinc, yet we still make able to make beer, right?).

There is mention that inadequate zinc levels can cause problems with the yeast, but I've didn't come across where this has actually been an issue. I believe one of the ideas behind yeast nutrient (its basically yeast/yeast byproduct) is that it has zinc in it from all of the yeast cell bodies in there.

Its suspicious to me that JZ/CW would make such a statement like that, but not tell you how to fix the problem. Again, are you sure you read it right?

Yeah, if it were something that would really benefit the brew, their highnesses would have already told you how much to add and how to get it in there properly.

Wyeast nutrient has zinc in it.

i think servomyces contains zinc and it is important for yeast health especially if you're reusing your yeast.
the brewer at the local micro adds it and i have to ask him for the amount again but i seem to remember it being a small percentage of f@$% all,it was a really tiny amount. i'll ask him the next time i see him unless someone else chimes in with the answer.

When I get home I'll look up the exact quote and post it.

Does anyone know where to find zinc whithout anything else in it? When I was at Siebel, we were told you want about 1 ppm in your wort.

indianaroller said:

Does anyone know where to find zinc whithout anything else in it? When I was at Siebel, we were told you want about 1 ppm in your wort.

Click to expand...

I think a better question is: How much zinc ends up in wort from the normal brewing process?

Instead of looking for a product to fix a problem, it might be good to ask if a problem exists in the first place....

indianaroller said:

Does anyone know where to find zinc whithout anything else in it? When I was at Siebel, we were told you want about 1 ppm in your wort.

Click to expand...

I know where to find zinc with nothing else in it but there is something on it. Modern pennies are made of copper plated zinc. I suppose you could put a penny in a vice and file it. The filings would be 97.5% zinc and the rest copper. But modern thinking is that copper should be avoided. I guess you could put some pennies in nitric acid until the cladding is dissolved. What's left would be pure zinc but I don't like the idea of people fiddling with nitric acid.

Best thing would probably be to get some zinc sulfate (food grade = FCC) and use as much of that as is necessary to obtain 1 ppm (or whatever the magic number is).

Here's what the book says: "An all malt wort contains all the nutrients yeast need for fermentation except oxygen and zinc..."

"...As we mentioned earlier, wort is often zinc limited. Zinc is important in the cell cycle (reproduction) and is a co-factor for alcohol dehydrogenase, the enzyme responsible for alcohol production. Even though other metal ions might be present, there is no substitute for zinc. The ideal range for fermentation is 0.1-0.15 milligrams per liter. You can use either food grade (FCC) or pharmaceutical grade (USP) zinc sulfate or zinc chloride. One thing to be aware of when determining dosage and cost is that the FCC or USP grade of zinc sulfate is invariably zinc heptahydrate salt (ZnSO4 - 7H2O, which is only 23 percent zinc by weight. On the other hand, zinc chloride is 48 percent zinc by weight. Also, keep in mind that some of the zinc is absorbed by the hot break, and you will need to add more than the target amount for fermentation. Adding approximately 0.2 to 0.3 mg/L of zinc near the end of the boil should result in a high enough zinc level in the fermenter."

Obviously there is at least some merit to this or it wouldn't be in the book. However, all it says is that "Zinc is important in the cell cycle..." and doesn't specifically say what the effects are of not adding it. Most of us do not add Zinc and make fine beer. What I'm really wondering is if anyone else buys into this and what kind of actual experience they have with it.

I haven't really been doing it long enough to notice a difference, but I have started adding zinc to my beers since reading the yeast book. I do feel like it's made my yeast take longer to flocculate. I've been thinking about only adding it to starters instead since its main function seems to be yeast replication.

stageseven said:

I haven't really been doing it long enough to notice a difference, but I have started adding zinc to my beers since reading the yeast book. I do feel like it's made my yeast take longer to flocculate. I've been thinking about only adding it to starters instead since its main function seems to be yeast replication.

Click to expand...

How much are you adding?

stageseven said:

I haven't really been doing it long enough to notice a difference, but I have started adding zinc to my beers since reading the yeast book. I do feel like it's made my yeast take longer to flocculate. I've been thinking about only adding it to starters instead since its main function seems to be yeast replication.

Click to expand...

Yeah and what form of zinc are you using? Can you just grind up a couple of zinc vitamins for a 5 gallon batch?

Here's a quick read about adding zinc.

Click on the link. Read the ad. Click on "click here to proceed to link destination".

Good info - worth the extra CLICK.

http://blog.cara-online.com/2010/09...-supplementation-of-wheat-beer-fermentations/

I have noticed that some brewers use galvanized valves
Maybe thats an option?
Zink is also toxic if you add to much so dont add any before you know how much the yeast will absorb

Servomyces and Wyeast nutrient both have zinc in them. While Servomyces is a bit pricy, Wyeast nutrient is very reasonably priced. I use Wyeast nutrient in every batch and have great fermentation and attenuation. If you are concerned about a lack of zinc, you should probably use a product that is designed for yeast health and fermentation from a reputable vendor rather than just randomly dumping zinc in your wort.

So I did some reading from Google Books...here is some info from Brewing: Science and Practice by Briggs et al.

http://books.google.com/books?id=zV...t&pg=PA163#v=onepage&q=zinc beer wort&f=false

Zinc Concentrations in Sweet Worts from Published Studies (from Table 4.23):

Wort A: 0.12 mg/L zinc
Wort B: 0.07-.16 mg/L zinc
Wort C: 0.1-0.3 mg/L zinc

Briggs et al. recommend a Zinc level of 0.1-0.2 mg/L and Zainasheff/White recommend 0.1-0.15 mg/L (this is from JonK331's post earlier in the thread).

So if we assume if Worts A, B, and C are representative of your typical worts, then you can argue that zinc supplementation is not necessary. All of these worts have the recommended amount of zinc in them (or pretty darn close in the case of the range in Wort B).

Briggs then goes on and states that zinc supplementation may be necessary (cites three references), and for the following reasons:
1. Inorganic ions (such as zinc) may not be adequately extracted from the grains during mash. Only 5% of zinc may end up in the wort post-mash.
2. Of the zinc that is extracted, some may be chelated or otherwise unavailable to the yeast.
3. Consequently, analysis of zinc content is unreliable for determining if there is zinc deficiency. So I'm not sure what this means for the numbers in Table 4.23...does it mean those aren't valid?

My take on it (FWIW): I have no doubt that zinc is important for proper yeast growth and fermentation. But right now I'm skeptical that zinc supplementation would make all that much difference. Even if a wort was zinc deficient, it sounds as if analytical tests would have trouble picking it up. Furthermore, based on the numbers in Table 4.23, it appears that wort may have the proper levels of zinc anyway, without supplementation.

That being said, I can see where it could be a problem though as I can envision a scenario where zinc is poorly extracted from the mash and/or not available for uptake by yeast, leading to a zinc deficiency.

I don't have the time to look right now, but I'd like to see some an instance of where a wort tests and actually has a zinc deficiency (less than 0.08 mg/L). I'd also like to see what effect that has on yeast fermentation (if any).

I specifically use Wyeast nutrient over the "standard" DAP nutrients because of the additional zinc. The issue is not necessarily the concentration of zinc in the wort, but how labile it is.

For me, the nutrient is just one form of cheap "insurance" - it's pennies per batch, and I haven't had a stuck ferment or long lag times (unless I screwed up my temp control) since I started using it. Is it possible that I could get similar results without the nutrients? Possibly, but I am not really willing to do the experiment because I feel like my process works well for me. Likewise, if you get great results without additional nutrients, there is little need to add any.

It probably makes a bigger difference to people who tend to underpitch because they don't rehydrate their yeast or don't make starters (or at least not sufficiently large ones). In those cases, the yeast need to propagate in the main wort/beer, at which point nutrients like zinc can become limiting.

I am sure that BBR or someone will do an experiment on this eventually.

The solubility of metals is directly tied to the pH of the solution (lower pH = greater solution of metals). I would not be surprised that reduced Zn content would be produced by having mash pH at higher than optimal level. Proper acidification of the mash may be more important than we currently know.

indianaroller said:

How much are you adding?

Click to expand...

Sorry, I haven't been on since yesterday. I've been adding 1/10th of a 50mg zinc gluconate vitamin tablet ground up. So 5mg zinc gluconate per batch. Figure 19 liters per 5 gallon batch, that's a requirement of 3.8mg. I know not all of that 5mg weight is zinc, so it's probably an underdose, but from what I've read zinc gluconate is one of the forms that's dissolvable in wort.

So my follow up reading to Chris White's yeast book has been George Fix's Principles of Brewing Science. It seems like this topic is the one direct contradiction. P. 66 of Yeast says "Zinc is the one compound that is often in short supply" within all-malt wort, but on P. 36 of Principles, Fix says "all malt worts tend to be sufficient in all three metals" (copper, iron, and zinc) and further goes on to say "some brewers directly add zinc to correct deficiencies that typically arise from high concentrations of unmated grains."

So I guess for my brewing, unless I notice a negative impact, or use a lot of adjuncts/unmalted grains, I'll stop adding zinc.

mabrungard said:

I would not be surprised that reduced Zn content would be produced by having mash pH at higher than optimal level.

Click to expand...

The equilibrium concentration of Zn++ WRT oxide or hydroxide is 1 mol/L (65 g/L) at pH 5.6 and decreases 2 decades per pH unit this at pH 6.6 it would be 0.01 mol/L (650 mg/L) and 0.1 mmol (6.5 mg) per liter. Thus I think plenty of it can be kept in solution (given that the desired concentration seems to be 0.1 - 1 mg/L.

Now where this gets interesting is that if you continue to go up in pH the decrease in solubility ends at about pH 9.7 or so. Increasing the pH further results in more, not less zinc in solution.

Zn(OH)2 + 2(OH)- ---> Zn(OH)4--

IOW zinc hydroxide is an acid as well as a base.

Now whether the zincate ion is assimilable by yeast or not is a different question. They would doubtless be dead at pH > 9.7 or at least not at their peak of fermentation performance.

That aside, the place where reduced solubility of zinc at increasing pH might need to be considered would be where lime treatment is being used to decarbonate. If the pH is taken to 10 or so zinc would only stay in the water to the extent of 0.0001 mmol (0.0065 mg/L) thus effectively de-zincing the water. But a kilogram of malt apparently contains about 20 mg of zinc.

Well, this subject was really bothering me between this thread and the other I made on problems experienced with my own DIY yeast nutrient, so I went ahead and emailed Chris White. Specifically I asked about the discrepancies between his and other publications on whether or not zinc is sufficient in all-malt wort, and what the best course of action is considering the dangers of adding too much zinc. Here is his response.

"Hello. Thank you for reading the book. Yes zinc is a bit controversial. When we look at the zinc in all malt wort, it seems to be enough on paper. But if you add more zinc, the fermentations are better. If there was enough available zinc, you should not see an improvment in fermentation. The zinc probably binds to protein and other material in the trub.

If you add mineral zinc, you can add too much. If the zinc is in servomyces you can go to higher zinc levels."

So it seems like more experimentation is in order, since even among brewing scientists there is disagreement as to whether zinc additions are needed.

I was planning on adding wyeast nutrient to a batch for the first time, but, alas, i forgot to pick it up. As per some of the above recommendations I will add zinc instead. I work in a molecular biology lab, so I have access to both Zinc Chloride as well as Zinc Sulphate. Using the info above (43% zinc by weight with the chloride and 23% by weight of the sulphate) I arrived on adding:

3mg of Zinc chloride -> 3*.43 = 1.29 mg Zinc
4mg of Zinc Sulphate -> 4*.23 = .897 mg Zinc

2.187 mg zinc in ~20L -> .11mg/L zinc

I brewed yesterday, and got a 1 L starter of 1056 going. When I go home tonight I will add the minerals to the stir plate starter and then pitch the starter with 45 sec O2 bubble. OG is 1.064. I will report results as they come.