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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 17 of 17. This is the beginning of the thread.
Posted by KaraS on March 27, 2005, at 23:23:43
Sometimes if I've opened a can and only consume part of it contents, I'll keep the food in the can and put some tin foil over it and then refrigerate it. Is this dangerous? Is aluminun leaking into the contents of the can or is some other bad reaction taking place?
Posted by rainbowbrite on March 27, 2005, at 23:59:21
In reply to Is it safe to leave food in the cans they came in?, posted by KaraS on March 27, 2005, at 23:23:43
somethiing happens that is bad but im not sure what exactly. I just know that it is bad to keep juice or food in cans once they are opened. I think a reaction happens when the air is let in but lol im am guessing as to the reason.
Posted by alexandra_k on March 28, 2005, at 5:14:51
In reply to Is it safe to leave food in the cans they came in?, posted by KaraS on March 27, 2005, at 23:23:43
I have heard it isn't so good.
But it hasn't killed me yet :-)
And pets seem to do ok.
Posted by Sarah T. on March 28, 2005, at 21:33:37
In reply to Is it safe to leave food in the cans they came in?, posted by KaraS on March 27, 2005, at 23:23:43
Hi Kara. When I was a child, my mother always used to tell us it wasn't safe to leave food in the can, but she didn't say exactly why. I very vaguely remember hearing that the warning applies only to certain types of foods. I'm sorry I don't know more about this.
Posted by Sarah T. on March 28, 2005, at 23:23:37
In reply to Is it safe to leave food in the cans they came in?, posted by KaraS on March 27, 2005, at 23:23:43
If I remember correctly, I think the warning against leaving food in a tin can in the refrigerator had to do specifically with acidic foods because the acid in the food might react with the tin. I don't know whether it's actually dangerous or whether this reaction just imparts a metallic taste to the food.
Posted by Racer on March 29, 2005, at 19:27:47
In reply to Re: Is it safe to leave food in the cans they came in? » KaraS, posted by Sarah T. on March 28, 2005, at 23:23:37
I don't know the answer, but I'm guessing that it applied to the old kind of cans, and not to the new, modern cans that we buy today.
But I'm only guessing. :-D
Posted by alexandra_k on March 30, 2005, at 2:11:41
In reply to Ummm...., posted by Racer on March 29, 2005, at 19:27:47
Google knows everything ;-)
I found this:
http://www.inchem.org/documents/jecfa/jecmono/v024je13.htm
Seems to apply to modern cans too.
Acidity makes the tin corrode so we tend to absorb more of it...
Posted by Dinah on March 30, 2005, at 22:35:27
In reply to Re: Ummm.... » Racer, posted by alexandra_k on March 30, 2005, at 2:11:41
Thanks Alexandra.
:)
I was just complaining to my husband that canned vegetables always taste a bit like can. Now I know that my taste buds aren't lying to me.
Here's to starting to pack veggies in recyclable bottles!
Posted by KaraS on March 31, 2005, at 1:07:25
In reply to Is it safe to leave food in the cans they came in?, posted by KaraS on March 27, 2005, at 23:23:43
I'm sufficently scared now to start putting the contents of cans into other containers. That's what I was hoping would happen when I started this thread.
Posted by Larry Hoover on March 31, 2005, at 10:34:03
In reply to Is it safe to leave food in the cans they came in?, posted by KaraS on March 27, 2005, at 23:23:43
> Sometimes if I've opened a can and only consume part of it contents, I'll keep the food in the can and put some tin foil over it and then refrigerate it. Is this dangerous? Is aluminun leaking into the contents of the can or is some other bad reaction taking place?
Sorry, I didn't know this thread was active, here in the bowels of Babble-land....
I did a year-long research project on potential toxicities/endocrine disruption which might arise from canned foods.
There are two sorts of cans. One is based on steel (the ones with a seam up the side, and ones based on aluminum (no side seam). Either one might be lacquered, to seal the metal against direct contact with the food.
The regulations which control food safety are designed to ensure that food stored in *sealed* cans does not become contaminated by bacteria, or pick up contaminants from the container itself. No provision is made for examining the effect of leaving the contents in an opened can. It's not part of the food safety standards, and it's assumed it does not happen.
However....
Some cans have obvious lacquer layers inside them. They may be opaque white, or the metal will shine from behind a slightly opaque surface. These tins are least likely to permit leaching from the can wall into the food.....of the metals behind the lacquer. The effect itself depends on time exposed to air. There is no air in a sealed can, which is the reason it remains stable so long. Add air, and the chemistry changes altogether.
I made a point of mentioning leaching of the metal behind the lacquer. You may also have leaching of the lacquer itself. I last looked at the literature about eight years ago, and at that time, there was significant concern about lacquer chemicals appearing in food. The European Union passed some strict legislation in that regard, and because of global trade, I would presume that everybody simply adopted those new regs (or you can't trade your product internationally).
There had been a significant issue of plastic monomers leaching into food, as the lacquer coatings were applied after the can was formed, via in situ polymerization. The efficiency of the polymerization process seemed to be no better than 88%, leaving the remainder to leach into food. I think they got that figure up to 96%, but that's as I recall it.
Anyway, leaving food in these tins after opening is creating a whole new chemical environment, with oxidizers leading the way. The oxidizers massively promote decomposition of the lacquer, and if there is the slightest imperfection in the lacquer seal, the metal of the container itself. The oxidation process forms free monomer/dimers (and other fragments), as well as soluble metal cations, which move into the aqueous food environment.
Here's a thinking point. Would you save empty (washed) tins to later use as food storage containers?
I think you can use the latter question to clear up any lingering doubt.
Lar
Posted by KaraS on April 1, 2005, at 0:44:30
In reply to Re: Is it safe to leave food in the cans they came in? » KaraS, posted by Larry Hoover on March 31, 2005, at 10:34:03
I promise I'll never do it again. Thanks.
Posted by KaraS on April 1, 2005, at 21:57:25
In reply to Is it safe to leave food in the cans they came in?, posted by KaraS on March 27, 2005, at 23:23:43
Gee, I wonder if it is safe to leave coffee in the tins it comes in. I think I'll empty the coffee into tupperware type containers from now on.
Posted by Larry Hoover on April 1, 2005, at 22:19:23
In reply to Re: Is it safe to leave food in the cans they came in?, posted by KaraS on April 1, 2005, at 21:57:25
> Gee, I wonder if it is safe to leave coffee in the tins it comes in. I think I'll empty the coffee into tupperware type containers from now on.
Sorry if I was unclear.....moisture is a critical factor. Dry products like ground coffee do not interact like I was describing. I keep my coffee in the can it came in, without any concern at all.
Lar
Posted by KaraS on April 2, 2005, at 2:12:21
In reply to Re: Is it safe to leave food in the cans they came in? » KaraS, posted by Larry Hoover on April 1, 2005, at 22:19:23
> > Gee, I wonder if it is safe to leave coffee in the tins it comes in. I think I'll empty the coffee into tupperware type containers from now on.
>
> Sorry if I was unclear.....moisture is a critical factor. Dry products like ground coffee do not interact like I was describing. I keep my coffee in the can it came in, without any concern at all.
>
> Lar
But there's moisture in the air and esp. in the refrigerator, isn't there?
k
Posted by Larry Hoover on April 2, 2005, at 9:22:10
In reply to Re: Is it safe to leave food in the cans they came in? » Larry Hoover, posted by KaraS on April 2, 2005, at 2:12:21
> > > Gee, I wonder if it is safe to leave coffee in the tins it comes in. I think I'll empty the coffee into tupperware type containers from now on.
> >
> > Sorry if I was unclear.....moisture is a critical factor. Dry products like ground coffee do not interact like I was describing. I keep my coffee in the can it came in, without any concern at all.
> >
> > Lar
>
>
>
> But there's moisture in the air and esp. in the refrigerator, isn't there?
>
> kModern self-defrosting refrigerators are dessicating pumps, moving moisture out of stored items.
The coldest part of the fridge is where the moisture in the air collects. It's a one way street (pretty much). So, the cold coil is the moisture collector for the fridge as a whole.
Air that has dropped its moisture load at the cold coil has regained the capacity to carry moisture again. Even at the cold ambient temperature of the fridge space, this air is drier than all the rest. So, as it migrates around in there, it pulls moisture from the only moist surfaces, food. Food dries, cold coil collects frost.
Now, it's true that putting a container in the fridge that has some sort of seal on it creates a little microclimate, and there can be coondensation inside the seal (if the air trapped there had a high moisture charge), but I doubt that would become a factor with a coffee tin.
The first time you open it, there is little space for air at all, and the coffee itself was surely packed dry. If you put that nearly full tin in the fridge, the contents become chilled. The next time you take coffee out, there is little space for air to enter the tin, and everything in there is cold already. And so on. I doubt you could ever really get a charge of moist warm air in the tin, unless you leave it to warm to room temp every time you open it.
That's my view, anyway.
Lar
Posted by KaraS on April 2, 2005, at 16:30:10
In reply to Re: Is it safe to leave food in the cans they came in? » KaraS, posted by Larry Hoover on April 2, 2005, at 9:22:10
> > > > Gee, I wonder if it is safe to leave coffee in the tins it comes in. I think I'll empty the coffee into tupperware type containers from now on.
> > >
> > > Sorry if I was unclear.....moisture is a critical factor. Dry products like ground coffee do not interact like I was describing. I keep my coffee in the can it came in, without any concern at all.
> > >
> > > Lar
> >
> >
> >
> > But there's moisture in the air and esp. in the refrigerator, isn't there?
> >
> > k
>
> Modern self-defrosting refrigerators are dessicating pumps, moving moisture out of stored items.
>
> The coldest part of the fridge is where the moisture in the air collects. It's a one way street (pretty much). So, the cold coil is the moisture collector for the fridge as a whole.
>
> Air that has dropped its moisture load at the cold coil has regained the capacity to carry moisture again. Even at the cold ambient temperature of the fridge space, this air is drier than all the rest. So, as it migrates around in there, it pulls moisture from the only moist surfaces, food. Food dries, cold coil collects frost.
>
> Now, it's true that putting a container in the fridge that has some sort of seal on it creates a little microclimate, and there can be coondensation inside the seal (if the air trapped there had a high moisture charge), but I doubt that would become a factor with a coffee tin.
>
> The first time you open it, there is little space for air at all, and the coffee itself was surely packed dry. If you put that nearly full tin in the fridge, the contents become chilled. The next time you take coffee out, there is little space for air to enter the tin, and everything in there is cold already. And so on. I doubt you could ever really get a charge of moist warm air in the tin, unless you leave it to warm to room temp every time you open it.
>
> That's my view, anyway.
>
> Lar
>
Ok, I'm convinced. It's just amazing how much you know!K
Posted by Larry Hoover on April 3, 2005, at 10:00:47
In reply to Re: Is it safe to leave food in the cans they came in? » Larry Hoover, posted by KaraS on April 2, 2005, at 16:30:10
> Ok, I'm convinced. It's just amazing how much you know!
>
> KYa, well. I do pretty well at trivial pursuit.
The thing about dry coffee is, that at a microscopic level, it's not really in good contact with the can surface. The air gap protects against migration, even if the can wall started to break down. Moist food is in intimate contact with the can, and the water actually forms a solvent bridge between the food and can.
Anyway, enough....
Glad you find my brain of some use.
Lar
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