[Clemente]

I purchased this can of Pineapple Chunks at my local Whole Foods store (upscale food products) and after opening it noticed a surprising coloration and pattern on the inner walls of the can. Looks similar to galvanized steel, a mottled irregular silver color I have never seen before on the lining of a metal canned food. Whole Foods mandarin oranges also has this finish. Label on can says its a Non-BPA Lining.

I bought a can of Whole Foods Peas in the same line of product, to see if both veggies and fruits have this same lining. The peas did not have this unusual pattern/coloration.

I was excited, thinking Whole Foods may be using a new type of lining that would greatly inhibit the more rapid corrosion of the inner can lining typically found in the most acidic of metal canned food products, pineapple being among the most corrosive, along with tomato products, sauerkraut and from what I understand metal canned beets are also in this category.

I've attached a few photos of the canned pineapple product with what looks like galvanized finish.

But then I did some reading and now I am not sure it is galvanized. My research online turned up some comments on different websites, here are a few (excerpts are bolded and italicized):

"Highly acidic foods, like pineapple, have to be protected from the steel, so the inside of these cans are typically galvanized using zinc, which is more corrosion-resistant than steel, or coated in plastic. Look inside the pineapple can — if you see a pattern of geometric shapes, sort of crystalline looking, it's galvanized."

Here are some excerpts from a different website. Note that those discussing the apparent look of galvanized metal in other metal food can interiors have different thoughts, some indicating it can't be galvanized interior as apparently there is a zinc component to galvanized metal which would be very reactive with acidic food products and therefore not be a useable choice for the inside of metal food cans, particularly those that are highly acidic. So my question is, what is the interior can lining of my Whole Foods Pineapple, and the Aldi's canned tomato product in the discussion below?

I am hoping whatever this interior lining is (which seems as though it may be used only or entirely on acidic food products) is being used to extend the length of time high acid food products will last in these cans so I can put away more acid food type products in my long term metal canned food storage without having to worry about the much more rapid interior corrosion of the can lining that is normal with high acid foods.

Galvanised metal in food cans
June 27, 2017 5:51 PM Subscribe

I just poured a can of tomatoes into the curry that I am cooking and am slightly concerned about the can that the tomatoes came out of. The can is unlined and the metal is clearly galvanised. This seems unusual to me for a food can, but I'm not sure whether I'm just being overly paranoid. It's been a while since I've come across any cans without some kind of plastic lining. Can I eat my curry without concern? For clarity: This is the only can of tomatoes I've ever bought from the particular retailer (Aldi), so I have no idea whether this is normal for them or not.

posted by kinddieserzeit at 5:54 PM on June 27, 2017


This is normal with tomatoes, because they are so acidic the plastic lining gets eaten away or something. I can't remember the last time I saw a plastic-lined tomato can.
posted by rabbitrabbit at 6:07 PM on June 27, 2017 [9 favorites]


To clarify, they don't line tomato cans usually... I'm not saying there used to be a plastic liner and the tomato acid ate it away!
posted by rabbitrabbit at 6:21 PM on June 27, 2017 [2 favorites]


Best answer:I've bought tomatoes in cans from various stores over the years, and I've never seen a can of tomatoes that had a plastic lining. They've always been galvanized metal, just as you saw. This may be something specific to Aldi's.
posted by Roger Pittman at 7:35 PM on June 27, 2017


metal is clearly galvanised

Do you really mean galvanised [i.e. plated with zinc], or just plated with some metal [usually it is tin]?

It would be problematic to use zinc in an acidic environment.
posted by HiroProtagonist at 7:39 PM on June 27, 2017 [2 favorites]


Response by poster:Unfortunately I don't really know my metals, so I'm unsure what kind of metal it is. The closest match I can find is probably this. And now that I've found a picture of a can that looks like this, I feel silly. It just reminded me more of a building material than material to make a can for food.

I'm used to cans with a shiny metal finish or white lining.
posted by kinddieserzeit at 8:00 PM on June 27, 2017


Pineapple also comes in zinc lined steel cans.
posted by rhizome at 10:48 PMon June 27, 2017



Best answer:Somewhat unhelpfully, steel cans are either "tin plate" or "tin-free steel" (TFS). There are also aluminum cans, of course.

If it's tin plated, there is probably a chromate conversion coating on top, and maybe oil or lacquer on top of that. If it's tin-free, it's chrome-plated, again with oil or lacquer on top. Tin plate is easier to weld. Is it a 3-piece can?

Zinc is mildly toxic and isn't used for food packaging.
posted by Huffy Puffy at 6:46 AM on June 28, 2017


Whatever it is, it's whatever has that polygonal shiny finish.

 

[NY Min]

Your can wasn't coated with one of the modern epoxy resins (not plastic) used for can linings with acidic food, and the pineapple has etched the metal already. Pineapple is very good at eating through cans, which is why canned pineapple is one of the things you should pay attention to the best-by date for.

The 365 is Whole Foods' budget store-brand line of foods. They aren't using anything fancy in those cans. You aren't seeing the etching/discoloration with peas you are seeing with pineapple and mandarin oranges because peas aren't an acidic fruit, simple as that.

If you want a longer storage time for acidic foods such as pineapple, sauerkraut, Harvard beets, etc. (and better taste and no toxic leaching after being in the pantry for a while) buy them in glass jars or can them that way yourself. Use a glass, plastic, or epoxy-lined lid on your home canning jars and store in an upright position so the lid is not in contact with the contents.

PS: If you want to know what the lining on the can is for a certain product, it's generally easier and faster to write and ask the manufacturer rather than taking a poll of a bunch of random people on the internet who may or may not know what they're talking about.

 

[Clemente]

Your can wasn't coated with one of the modern epoxy resins (not plastic) used for can linings with acidic food, and the pineapple has etched the metal already. Pineapple is very good at eating through cans, which is why canned pineapple is one of the things you should pay attention to the best-by date for.

The 365 is Whole Foods' budget store-brand line of foods. They aren't using anything fancy in those cans. You aren't seeing the etching/discoloration with peas you are seeing with pineapple and mandarin oranges because peas aren't an acidic fruit, simple as that.

If you want a longer storage time for acidic foods such as pineapple, sauerkraut, Harvard beets, etc. (and better taste and no toxic leaching after being in the pantry for a while) buy them in glass jars or can them that way yourself. Use a glass, plastic, or epoxy-lined lid on your home canning jars and store in an upright position so the lid is not in contact with the contents.

PS: If you want to know what the lining on the can is for a certain product, it's generally easier to write and ask the manufacturer rather than taking a poll of a bunch of random people on the internet who may or may not know what they're talking about.

Thanks for the clear answer here. Still don't care for glass storage for large, long term storage due to noticeable increase in earthquakes in many different places, and other increasing climate difficulties like increase in hurricanes. Very and increasingly unpredictable now where these things occur. One of these hits and poof, years of storage in glass gone. In metal cans much better chance of metal cans being spared, even when dented. Glass is just too fragile when compared to metal.

Don't metal canned foods have a substantially longer lifespan (i.e. safe to eat) than home canned glass canned foods? I know that taste, consistency and vitamin content decreases over time for both metal and glass, but I've read many accounts of food being eaten in metal cans that had no breach decades and even 50 years later with no ill effect.

I thought glass canned was typically considered safe for about a year, or maybe a few years after canned--or does glass home canned also last decades? Just thought there is much more risk as the sealing between the lid and glass jar is more at risk over time than the metal cans which last essentially forever if no breach/corrosion.

I understand about metal canned acidic foods and will only stock a very modest amount of these, expecting to eat those by expiry date, perhaps one year max after that to avoid corrosion issue.

 

[97guns]

I try not to keep fruits and tomato product too long, I’ve had fruit cocktail and apple pie/blueberry pie filling eat right through a can and it’s not even that acidic

I hate it when I open a can and smell or taste that metallic, I usually toss whatever it is

 

[NY Min]

Thanks for the clear answer here. Still don't care for glass storage for large, long term storage due to noticeable increase in earthquakes in many different places, and other increasing climate difficulties like increase in hurricanes. Very and increasingly unpredictable now where these things occur. One of these hits and poof, years of storage in glass gone. In metal cans much better chance of metal cans being spared, even when dented. Glass is just too fragile when compared to metal.

Don't metal canned foods have a substantially longer lifespan (i.e. safe to eat) than home canned glass canned foods? I know that taste, consistency and vitamin content decreases over time for both metal and glass, but I've read many accounts of food being eaten in metal cans that had no breach decades and even 50 years later with no ill effect.

I thought glass canned was typically considered safe for about a year, or maybe a few years after canned--or does glass home canned also last decades? Just thought there is much more risk as the sealing between the lid and glass jar is more at risk over time than the metal cans which last essentially forever if no breach/corrosion.

I understand about metal canned acidic foods and will only stock a very modest amount of these, expecting to eat those by expiry date, perhaps one year max after that to avoid corrosion issue.

Yes, glass can get broken more easily than metal gets dented badly enough to ruin the seal. Everything in life is a trade-off.

As for home-canned in glass versus commercially canned in cans, it all depends on protection from light (which deteriorates food just as moisture, oxygen, and heat do) and the lid seal.

The seamed metal lids of commercial tin cans hold up very well as long as there is no fault in the seal when formed, although the lid or side seam is where a can will generally fail when it finally does.

For home canning in jars, it's all about the seal. Some of the modern metal lids seem to have poor quality/skimpy sealant and don't fare as well past a couple of years as the older ones did. Rubber gasket-sealed lids, glass or plastic reusable ones, seem to generally hold up better as long as you get a good seal to start with, although getting that initial good seal can be a bit trickier, but still are unlikely to outlast a good metal seam. (But then that metal seam may outlast the food it is protecting. A can may last decades, but the food inside it won't, at least not as actual nourishing food. The cellulose still won't give you food poisoning doesn't really count.)

Canned food is safe to eat, i.e. still microbiologically safe, as long as the can is intact. Quality deteriorates over time, faster in some things than in others, and any food containing a lot of acid (or capsaicin) will slowly destroy a metal can. All neutral canned foods will become sensorily and nutritionally undesirable in less time than it takes a well-protected can to fail. The fact the contents still won't give you food poisoning is apt to be immaterial at that point

Canned moisture-containing foods are at best mid-term pantry storage, with dairy and acidic foods often having a good shelf life of only one to two years. Depending on circumstances, the longer shelf life in glass for the acidic foods may not outweigh the greater vulnerability even when wrapped in cushioning material in divided storage containers, but no wet food in cans is truly long-term storage food

Dehydrated/freeze-dried foods that are low-fat will store in metal cans/protected mylar with oxygen absorbers the longest. Even there, though, there is a hierarchy in shelf life depending on the type of food. And no complete diet will store in any form for 30 years.

 

[Clemente]

Yes, glass can get broken more easily than metal gets dented badly enough to ruin the seal. Everything in life is a trade-off.

As for home-canned in glass versus commercially canned in cans, it all depends on protection from light (which deteriorates food just as moisture, oxygen, and heat do) and the lid seal.

The seamed metal lids of commercial tin cans hold up very well as long as there is no fault in the seal when formed, although the lid or side seam is where a can will generally fail when it finally does.

For home canning in jars, it's all about the seal. Some of the modern metal lids seem to have poor quality/skimpy sealant and don't fare as well past a couple of years as the older ones did. Rubber gasket-sealed lids , glass or plastic reusable ones, seem to generally hold up better as long a you get a good seal to start with, although getting that initial good seal can be a bit trickier, but still are unlikely to outlast a good metal seam. (But then that metal seam may outlast the food it is protecting. A can may last decades, but the food inside it won't, at least not as actual nourishing food. The cellulose still won't give you food poisoning doesn't really count.)

Canned food is safe to eat, i.e. still microbiologically safe, as long as the can is intact. Quality deteriorates over time, faster in some things than in others, and any food containing a lot of acid (or capsaicin) will slowly destroy a metal can. All neutral canned foods will become sensorily and nutritionally undesirable in less time than it takes a well-protected can to fail. The fact the contents still won't give you food poisoning is apt to be immaterial at that point

Canned moisture-containing foods are at best mid-term pantry storage, with dairy and acidic foods often having a good shelf life of only one to two years. Depending on circumstances, the longer shelf life in glass for the acidic foods may not outweigh the greater vulnerability even when wrapped in cushioning material in divided storage containers, but no wet food in cans is truly long-term storage food

Dehydrated/freeze-dried foods that are low-fat will store in metal cans/protected mylar with oxygen absorbers the longest. Even there, though, there is a hierarchy in shelf life depending on the type of food. And no complete diet will store in any form for 30 years.

Well spoken, and speaks to me of balance, to have storage foods in a variety of packaging rather than all the eggs in one basket. Home canning in glass sounds good for those high acid products which we have read more than a few reports of corrosion breaching the metal canned goods. I do plan on learning glass canning going forward to have that balance in packaging and the benefits glass has over metal as mentioned.

 

[NY Min]

If you're in earthquake country, maybe wrap all your jars in bubble wrap and stick them in divided layers inside a metal barrel or similar.

Do they still make those aluminum rectangular containers with snap lock lids they used for some damn thing in WWII? (My father had a dozen or more of those, although my older brother made off with them all, I think for stashing ammunition under his house, drat him.)

Whatever you decide to try for protection in earthquake/hurricane country, can some water in jars, pack it up, and try dropping it in its protection at least 4 feet onto cement. (In tornado country, just get it all underground). Or you could just ship it to a distant friend via FedEx/UPS. If it all arrives intact, you've got iron-clad protection that will probably survive at least a category 4 hurricane or a Richter 8 earthquake. Store as close to ground level as possible on industrial metal shelving bolted into the studs and with ship-style railings to prevent items sliding off.

 

[Clemente]

If you're in earthquake country, maybe wrap all your jars in bubble wrap and stick them in divided layers inside a metal barrel or similar.

Do they still make those aluminum rectangular containers with snap lock lids they used for some damn thing in WWII? (My father had a dozen or more of those, although my older brother made off with them all, I think for stashing ammunition under his house, drat him.)

Whatever you decide to try for protection in earthquake/hurricane country, can some water in jars, pack it up, and try dropping it in its protection at least 4 feet onto cement. (In tornado country, just get it all underground). Or you could just ship it to a distant friend via FedEx/UPS. If it all arrives intact, you've got iron-clad protection that will probably survive at least a category 4 hurricane or a Richter 8 earthquake. Store as close to ground level as possible on industrial metal shelving bolted into the studs and with ship-style railings to prevent items sliding off.

Bubble wrap mfrs must be doing well these days, a very useful product for the community.

Yes, lots of steel strapping to keep those shelves up.

I believe you are speaking of Bento boxes, which are still alive and well. I bought a couple of them recently, basically a partitioned mess kit for your meat, rice and beans. They have those metal hasp clasps that lock down nicely. Plenty available on Amazon.

 

[NY Min]

No, no, these were about 3/8" thick aluminum, about 15" wide and 20-24" long by 8" deep with a tight lid that lapped over the bottom and snap locks either end. Nothing like a bento box. Dimensions above approximate, haven't seen them now in over 20 years, since brother made off with them all, but they were great storage, probably designed to survive drops from planes.

 

[NY Min]

Bubble wrap mfrs must be doing well these days, a very useful product for the community.

I actually prefer the biodegradable waffle-cut paper padding, but good packing material is always useful.

 

[Clemente]

No, no, these were about 3/8" thick aluminum, about 15" wide and 20-24" long by 8" deep with a tight lid that lapped over the bottom and snap locks either end. Nothing like a bento box. Dimensions above approximate, haven't seen them now in over 20 years, since brother made off with them all, but they were great storage, probably designed to survive drops from planes.

Sounds like they might make good heavy duty Faraday cages too.

 

[NY Min]

Sounds like they might make good heavy duty Faraday cages too.

If so, sneaky brother has some of his electronics hiding in a couple as well. Double drat him.

They were like this one from WWII, only plain aluminum and with snap locks just at the two ends. Probably bought as end-of-war surplus before they whapped any olive paint on. Great storage.

I suspect well-cushioned jars in those would survive an earthquake about as well as #10 metal cans. And they're supposedly waterproof as well. Unfortunately, I'm sure not selling now for what they did in 1946.

 

[hatchet jack]

Could you dump the contents of the can in a jar and then use a vacuum sealer to suck the lid down and store the acidic foods that way?

 

[NY Min]

Could you dump the contents of the can in a jar and then use a vacuum sealer to suck the lid down and store the acidic foods that way?

Huh, wha?!?

Only temporarily in a refrigerator. There's a reason they process food inside closed containers with high heat when canning food to be shelf stable.

 

[Illini Warrior]

there's a coating there that you can't see - totally transparent - in the trade they refer to it as "varnish" - they coat all the beverage cans also - the white poly lining you are seeing in some cans is just another method when transparency isn't important .....

How Cans Are Made | Crown

Take a look inside how this modern marvel is made.

www.crowncork.com

 

[e.honey.m]

I have some sort of crazy moisture problem in my pantry that is unfindable and indefinable. I'm at a loss. So, I had lots of canned pineapple stored and the edges of the cans began to rust so I canned it all. I now have glass jars of pineapple. I use a lid called "for jars" instead of the old standby Ball lids. Ball sold out and has a lesser sealant on their jars and I believe the latest Ball recommendation is just 18 month shelf life and that is awful. These new lids I am using have had a 100% success rate so far, and i love the quality.

 

[Clemente]

I have some sort of crazy moisture problem in my pantry that is unfindable and indefinable. I'm at a loss. So, I had lots of canned pineapple stored and the edges of the cans began to rust so I canned it all. I now have glass jars of pineapple. I use a lid called "for jars" instead of the old standby Ball lids. Ball sold out and has a lesser sealant on their jars and I believe the latest Ball recommendation is just 18 month shelf life and that is awful. These new lids I am using have had a 100% success rate so far, and i love the quality.

Yes, that pineapple in metal cans is super corrosive. Bought the large size can of pineapple juice and black corrosion where I punched the hole on top appeared even though refrigerated, opened the can top completely and more black corrosion on insides. Glass canning definitely the way to go, that's what I would do for future.