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Safety of Galvanized Steel in smokehouses

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Q. I am considering using the shelves of an old refrigerator in my smokehouse (presumably galvanized). I usually do not exceed 250 °F. Am I going to potentially permeate my food with harmful fumes? Thanks.

Rob Prucha
- Missouri Valley, Iowa, USA


++

A. Should be fine for a cold smoker. Watch out for cadmium coating, though in some old fridges.

Ian Mcrae
- Australia


A. Hi. I suppose a really old fridge could possibly have galvanized or zinc plated shelves, but I think nickel plating would be most likely.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



+++

Q. I have constructed a meat (sausage) smoker from galvanized steel. It consists of a separate fire box and main unit which are attached by a 6" diameter tube, typical heating ducts. The food itself does not actually come in direct contact with the metal but hangs in the main box. Is there a health risk if I do not remove the coating from the inside of the smoker? If so can I remove the coating fairly easily with a disc grinder or simply burn it off?

Brian Dunn
- Windsor, Ontario, Canada


+++

A. Hi Brian,

Disclaimer: I'm not taking any responsibility if your 'galvanized' box has Cd plating (or if something else fails, either). Use this advise as a safety guideline and don't try anything unusual - > you should be safe. The 'galvanized' smoking box is presumably coated with zinc, i.e., gray colored metal possibly with the distinctive surface patterns. We generally don't get enough zinc in our nutrition and generally a small increase in gain is welcome as extra zinc washes off from our body and does not accumulate like many other heavy metals. To ensure adequate gain of zinc, zinc gets to be added into our fertilizers in many parts of the world.

For an average human the *safety limit* here in Europe these days is as much as 1 mg of zinc daily per body kilogram. Perhaps somebody can quote local daily limit if it differs.

If an average person weights 70 kg (or 175 pounds), such a person can take safely about 70 mg of zinc daily. The amount of zinc a person *requires* daily is far less, though.

(Though, during pregnancy women *require* about double amount of zinc than humans usually. As I recall, lots of zinc is required for cell division that happens during pregnancy).

(For example for metallic lead the same safety limit is 3.5 µg daily per body kg. Lead accumulates into our bodies, too which is a disadvantage).

So I suspect your zinc galvanized steel is safe for food manufacturing as long as the (sour) food juices do not come into direct contact with the zinc plating of your smokebox. I recommend you use some sawdust powder on the bottom of your smokebox to prevent the dripping acidic juice of fishes from corroding the galvanized plate on the bottom of box. (Oh, you already did that - WOW !)

The fumes from some burning sawdust powder and burning flesh that occurs in the smokebox generate PAH compounds that can cause cancer too, but that's not under discussion here. Generally, most or all extra zinc we get washes off from our bodies but at least the standards do not recommend more than total daily gain of 1 mg/kg here in Europe. (No more than that even for pregnant persons).

Sincerely, Mr. "Know-it-all"

Kari Alakuijala
- - OULU, Finland, EUROPE


+++++appended

Q. I recently obtained a galvanized barrel that I want to make into a smoker. A friend told me that the fumes from the galvanized barrel could harm the cooking or get into the cooking. Is that correct? What temperature does this occur at, if it does, and would you recommend that I get another type of barrel for a smoker?

Thanks,

Larry Carr
homeowner - Parkville, Missouri, USA


+++++

A. Well, Larry, zinc metal, the main ingredient in most 'galvanized' platings, melts at 692.68 K -or- 419.53 °C -or- 787.15 °F. But there are other plating metals, too. Demand zinc plated sheets - make sure you got zinc plated sheets first before constructing a smoker.

It's not recommended to keep the smoking box on open fire either, as it might cause the zinc metal to (partly) melt (and oxidize which would cause excessive zinc fumes ruining the cook). Please wait until the fire mostly dies out -to embers. Please cover the fire facing metal plate completely with (alter) sawdust. (I think alter smoke is what most people in Finland consider the best for smoking fish and food?)

Perhaps also, a completely iron box made of iron sheet metal or discarded, burned oil barrel would suffice for you for your 1-time or 1-summer use. The rust inside the barrel gets to be converted mostly to magnetite by heat and moisture coming from the cook. Magnetite somewhat prevents rusting of the barrel and the rusty old oil barrel may well last one summer and turn black (=rust turning into magnetite).

Kari Alakuijala
- OULU, Finland


+++++appended

Q. I want to convert an old galvanized water cistern into a smokehouse. Is it safe or will it poison my meat?

Michael Henderson
hobbyist - Lufkin, Texas


A. Hi Michael. The coating on a cistern was considered safe enough to drink from; zinc is an essential nutrient, not a poison, and it will not poison your meat.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



April 13, 2011

Q. I have been using a 1 inch x 1 inch spaced galvanized fencing for years to cook chicken, and so have many of my friends. We were told that heating the racks over high heat for 3-4 hours would burn off the galvanized coating. Were we wrong? Like I said I have used my racks for at least 10 years. Thanks,

Duke Marmet
- Glenmont, Ohio, USA

A. Hi Duke. Yes, most of the zinc probably burned off. Surely very little of it came off onto your chicken in even the worst case, and zinc is a nutrient not a poison anyway. Personally, I'm not a paranoid, sky-is-falling, guy -- so I wouldn't hesitate for a second to eat the chicken. But hopefully this will help you understand the principle of the thing:

1. Zinc is not considered a food-safe surface because certain foods can at least theoretically dissolve some of it into your food, and as a matter of practice you don't want dissolved metal in your food.

2. Fencing was not intended to be cooked on, so:
  a. There is no guarantee that the fencing has a pure zinc coating rather than some experimental material that might be fine for fencing but not good to cook on. Who knows?
  b. When we use a material for a purpose for which it wasn't intended, there are no researchers, epidemiologists or government agencies tracking whether any problems are occurring due to it. So not only do we not actually know if the situation is a problem, but we never will unless the effect were truly dramatic ... like multiple people dieing on the spot at a barbeque :-)

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



+++

Q. I believe my question applies to this discussion.

I am building a home-made smoker for fish and other meats. I purchased a 30 gallon galvanized steel trash can from my local Lowe's hardware store and intend to use it for both hot and cold smoking.

During some recent research, I stumbled on a forum post which suggested that the zinc on the galvanized steel could vaporize during the smoking process and could poison the food in the can. Obviously this is a concern for me.

In the hot smoking process, air temperatures in the can should never exceed 275 °F. With a 1200 V hot plate in the bottom of the can, I would expect the highest temperatures to be in that immediate vicinity. The food will never come in direct contact with the can, only with the steel grills I am using as meat racks.

Additionally, I will be using the lid of a metal trash can as a water dish which will be suspended a couple of inches above the chip dish and hot plate at the bottom of the unit.

Does anyone see a potential health problem with what I am doing here? I've seen a few other folks on the Internet using this type of trash can smoker, but I can't tell if they used aluminum, galvanized steel, or what.

Any advice is much appreciated.

-- Smoker =)

David Greenwood
- Auburn, Washington


+++

Q. I submitted a question to you yesterday regarding the use of galvanized steel in my homemade smoker. Since I wrote that email I found additional posts on this board where you discuss your concern about someone potentially using cadmium-coated steel. My new question is if there is any way I could tell if the steel I was using is cadmium-coated?

The 31 gallon trash can I have used is made by Behrens, Inc. I have tried to locate a home page for them in the hope that they might describe their process, but I was not able to find anything. While the sticker on the can does say "galvanized sheet", it says nothing else about the materials used.

To complicate matters, I am using the lid from a smaller galvanized can as a water dish at the bottom of the smoker. Because it is the closest item to the actual heat source, I am most concerned about its properties. Unfortunately, I did not buy the rest of the can at the same time, and I did not take note of the manufacturer. The lid seems to have what I would describe as a crystallized appearance, whereas the can does not.

You have stated that each individual needs to choose for themselves what they consider to be a threat to their health. Some might be willing to take a chance, and others not. You say it is difficult to tell which health warnings to take seriously, and which ones not to. I understand and agree. I am, however, going to be giving away a large amount of what I smoke, and I want to feel comfortable doing so. If you could pass on any more of your expertise I would be much obliged.

Thank you.

David Greenwood(returning)
Food products - Auburn, Washington

Build a Smokehouse


Meat Smoking and Smokehouse Design


(2003)

A. Hi, David. Cadmium electroplating would not have ever been used on trash cans in my estimation, although I haven't studied the history of that trash can manufacturer. If you see the typical "spangled" look of hot dip galvanizing, then you have further confidence that they were galvanized (dipped in molten zinc).

My personal opinion is I don't think there's any problem with what you are doing as long as you and the readers realize that there is to be no contact with the galvanized surfaces (because galvanizing is not a food-safe coating).

But any time you re-purpose materials that were not intended for food service, and introduce them into the food preparation cycle, you have the problem that regulatory authorities and medical researchers generally don't do research on it. Once in a while you may find a United Nations WHO article about it if it's a common third world practice -- but not finding such articles is not proof that such re-purposing has been found to be okay. Sorry, but that's just the way it is -(

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


+++++++

A. This is in response to the steaming fish with the galvanized garbage cans question. I wouldn't do it based on a recent experience I had where I was using a brand new galvanized watering container (made for animals to drink out of) as a way to put water vapor into the air (on top the wood stove). I got sick for four days after about 4 hours exposure to the vapor. It might not have been that, but I had all the symptoms of metal fume fever.

Just my two cents ...

Robert Cartmin
- Hartwell, Minnesota


July 25, 2011appended

Q. I have made a trash can smoker and was wondering if since it only gets up to 250 °F is it ok? Just wondering since I hear it takes much hotter temps to create a zinc problem.

Cary Worley
Hobbyist - Altoona, Iowa

June 2011

A. Hi, Cary.

Per my response to David, my personal opinion is that it's not a problem. But then again, who do I think I am that people should rely on my guesses?

The issue is that a real investigation of whether it's dangerous or not will probably never be done. To test one prescription drug costs millions of dollars and involves a rigorous protocol where exact dosages are administered under exact conditions, and the psychological factors are eliminated by nobody knowing who is taking the placebo vs. the real thing.

So that sort of real answer will never be forthcoming. On the other hand when something is really and obviously dangerous -- like mercury vapors in hat making, chromium fumes, or lead in paint -- it usually comes out fairly quickly. So we can probably say that a trash can smoker is significantly less risky than those :-)

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


 

Q. To Experts; I am in the meat processing business (not for USDA certification)local business.

I am building a Meat Smoker that is mostly mostly made out of Aluminum and steel. This will be heated by 240V Elements up to about 300 °F at the most.

The question I have is the meat will not touch any surface of the smoker except the hangers that are stainless steel. But I was going to use galvanize sheeting (same as home heating vent work) for the inside of the door and a small portion of drip pans, ventilation and such.

I don't believe the galvanized metal would get any amount of heat over 400 °F but after reading on this and other sites on the web I wonder if I am going to have the possibility of toxic fumes.

I would use aluminum or stainless but they are either hard to work with or very pricey for the size of sheets I require.

Thank You,

Craig B deleted
- Cincinnati, Ohio


I would not do it, Craig.

It's not a matter of any real danger in my opinion; rather, it's that as a business I feel you should not take the shortcuts that an individual might for his own use. I think you should use 'professional grade' materials (stainless steel) throughout.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



May 24, 2013appended

Q. I used galvanized racking in a smoker and was told that I could be poisoning people that eat the meat that is smoked. It doesn't get over 250 degrees. If so I will have to redo the smoker?

Ed Hosen
- hancock, Wisconsin


May 29, 2013

Hi Ed. As you see, we appended your inquiry to a thread where the topic has been discussed at length. Good luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


June 22, 2013

Plating *removal* tip.

It might be a good thing to first break-in, or make a running-in of the smoker to lessen the chance of any plating metal-fever.

First set up your DIY smoker to smoke something heavy, inert object like an old porcelain toilet seat smashed and pieces hung on the meat racks. When you see your smoker standing after at least one longer trial run, loaded to the max, on high heat, it's structurally sound. When you see no more white smoke escaping, you've probably burned away some of the fire-facing hotplate-exposed zinc in form of some smoke escaping. Try not to inhale the smoke. After running-in please remove the ballast from the meat-racks and start using (on your own risk).

I've used zinc-plated, purchased smoke box and the results were delicious. I recall didn't run-in. Though usually I discard the metallic-tasting fish skin.

A disposable aluminium barbeque I've never used. Low melting temperature on aluminium too. Remember those aluminium kettles we used to have back in the '70s but no more: aluminium fumes are a risk factor on Alzheimer's. Nobody has yet denied aluminium barbeque sale, at least here in Finland. Their use is very seldom, though..

Kari Alakuijala
- OULU, Finland, Europe


June 24, 2013

Hi Kari. Thanks! But the Alzheimer's Association does not really agree with you about the link to aluminum. I think the main reason aluminum is rarely used is the melting point is too low (it's easy to melt aluminum cans in a BBQ pit).

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

July 29, 2013

Q. Hi Ted,

How about the Al-containing plaques in the brain, found in studies near nasal cavities in Alzheimer's. Aluminium is not a bio-necessary metal. If the aluminium is not there, it can't get into brain to form plaques.

BTW. Here's a simple test I constructed to improve guessing which coating is on the metal. Google for 'Anodic Index'. You should get following voltages for various metal coatings. Voltages in salt brine (NaCl+H2O):

-0.35V for pure Copper metal
-0.60-0.65V for tin-plated sheet metal
-0.80V for Iron (nails, wire, untreated iron sheets)
-0.90V-0.95V for Aluminium, Cadmium coating or Aluminium coating
-1.20V for hot dip galvanized (Zinc-iron compounds)
-1.25V for Zinc electroplated, or pure Zinc

In this sample testing I used pure copper wire as a cathode.

When anode is coated with:
-Sn, you get 0.30V --> coating probably melts in a smoker
-Fe, you get 0.45V --> Your smoker will rust soon
-Al or Cd, you get 0.60V --> toxic coating, danger !!
-Zn, you get 0.90V --> highly desirable coating for smoker

Kari Alakuijala
- Oulu, Finland, Europe


July 2013

A. Hi Kari. Thanks for the chart.

I don't advocate for or against zinc vs. aluminum. What I advocate for is science & common sense & calm; what I advocate against is "toxic timebomb in your kitchen!" news reports, because they make our short lives less pleasant while richly rewarding news organizations and politicians for causing heartache and paranoia.

I am 100% open to the possibility that aluminum is not good for us but I must rely on competent researchers to make those determinations, and quoting the Alzeimer's Association:

" . . . The vast majority of mainstream scientists now believe that if aluminum plays any role at all in Alzheimer's, that role is small. . ."
". . . most mainstream health professionals believe, based on current knowledge, that exposure to aluminum is not a significant risk factor. Public health bodies sharing this conviction include the World Health Organization (WHO), the U.S. National Institutes of Health (NIH), the U.S. Environmental Protection Agency (EPA) and Health Canada. . ."
" . . . Further, it is unlikely that people can significantly reduce their exposure to aluminum through such measures as avoiding aluminum-containing cookware, foil, beverage cans, medications and other products. . .""

These organizations may change their opinion, and if & when they do, I'd probably change mine. Thanks again.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

December 3, 2013

A. I've been using a galvanised trash can as a smoker for a few years now. It sits on top of a portable gas ring. The safety angle hadn't occurred to me until last week, when someone was horrified at the thought of zinc fumes in food.
My response was that a) (as has been said in this thread many times) zinc is an essential trace mineral and you can buy pills of it, b) breathing fumes is not the same thing as eating them. Yes you can get sick breathing the fumes, as you would welding or whatever, but ingesting the small amount that adheres to any smoked food should do no harm and may be beneficial.
The bottom has almost rusted out of my can now, so obviously the zinc has gone.

Bronwyn Carlisle
- Dunedin, New Zealand

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