How do they process canned food?

[Muse]

I've often wondered about this. It's always seemed to me that food you buy in cans has an indefinite shelf life. Canned beans, mushrooms, soup, tomato paste, whatever it is, keeps on the shelf until you open it. Then, it's fair game to micro-organisms -- you refrigerate it after opening, use within a reasonable time frame or it spoils, either from fungi, bacteria or both.

What keeps it "fresh" when canned? Do they seal it in a vacuum? Do they have it hot (say above 160 F) when they seal it? How do they keep living micro-organisms from getting into the contents when canning it?

Same goes for bottled foods. Often, especially with bottled food, they add preservatives, so obviously the contents will go bad faster if they don't add the preservatives and presumably there's a time limit on how long you can expect the contents to taste fresh or maintain its nutritional quality.

I was running low on sweet pickle relish lately and priced a 12 oz. bottle of Del Monte at my local favorite market and was appalled that they were asking $2.79. I remembered seeing a gallon bottle of sweet pickle relish at Costco for under $5. So, I bought said gallon of relish there a week ago. Granted it's not Del Monte (Kruger), but it was $4.39, around 8 times cheaper than the Del Monte. It's got some preservative in it (Potassium Sorbate) and it says refrigerate after opening. Can I rebottle this stuff, or just figure I'm going to have to throw out most of it?

 

[bignateyk]

I think its vacuum sealed. (which is why canned goods have to be boiled, which is what creates the seal?)

 

[Darthvoy]

from what i know some are cooked after being sealed...that or they put Potassium benzoate to keep mold from growing?

 

[StrangerGuy]

They cook the stuff inside to kill every living sh1t in there after canning, so there. However, tin cans are very suspectible to rust once the plating gets scratched and the food goes rotten very quick.

 

[imported_Baloo]

The food is cooked in the can. It is already sealed before cooking. They are then cooked so thouroughly, that all micro-organisms are killed. They have shelf lives measured in years. Pretty much as long as the can remains sealed, the food inside is fine. Usually nitrogen is put in the air gap at the top of the can, or jar, to prevent food oxidizing. Some food, primarily in jars, are cooked without a lid, again very thoruoghly, but are lidded before the cooking process is complete.




....Tin cans don't exist anymore.

 

[Eli]

The process of canning is what prevents the food from spoiling.

The food is cooked, and sealed in a can, thus preventing spoilage.

 

[sniperruff]

look up UHF.

 

[Muse]

Originally posted by: sniperruff
look up UHF.

Umm, ultra high frequency radiation?

From Wikipedia:

UHF may refer to:

* Ultra high frequency
* Ultra High Frequency (rock band), a New York rock band
* Unrestricted Hartree-Fock
* UHF (film), a 1989 cult comedy film starring "Weird Al" Yankovic
* UHF - Original Motion Picture Soundtrack and Other Stuff, soundtrack to the film
* UHF (song), theme song to the film, single, and music video by "Weird Al" Yankovic
* UHF (band), a Canadian folk music supergroup
* UHF (rock band), a Portuguese rock band
* UHF (Ultra High Frequency), a 1990s alternative fashion magazine spun off from Option
* UHF connector, a type of RF connector

 

[sao123]

high temp cooking + vacuum sealed + excessive salt = germ free food.

 

[OverVolt]

Originally posted by: sao123
high temp cooking + vacuum sealed + excessive salt = germ free food.

+proper acidity

 

[FoBoT]

they cook it

 

[sniperruff]

Originally posted by: Muse

Originally posted by: sniperruff
look up UHF.

Umm, ultra high frequency radiation?

From Wikipedia:

UHF may refer to:

* Ultra high frequency
* Ultra High Frequency (rock band), a New York rock band
* Unrestricted Hartree-Fock
* UHF (film), a 1989 cult comedy film starring "Weird Al" Yankovic
* UHF - Original Motion Picture Soundtrack and Other Stuff, soundtrack to the film
* UHF (song), theme song to the film, single, and music video by "Weird Al" Yankovic
* UHF (band), a Canadian folk music supergroup
* UHF (rock band), a Portuguese rock band
* UHF (Ultra High Frequency), a 1990s alternative fashion magazine spun off from Option
* UHF connector, a type of RF connector

dorry i meant UHT

http://en.wikipedia.org/wiki/U...temperature_processing

 

[Muse]

Originally posted by: OverVolt

Originally posted by: sao123
high temp cooking + vacuum sealed + excessive salt = germ free food.

+proper acidity

Right. Since I started adding citric acid to my canned tomato hot sauce, I've had much better luck with it once I open and put in the refrigerator. It used to start tasting bitter in less than a week. Now, it lasts for weeks.

Originally posted by: sniperruff


dorry i meant UHT

http://en.wikipedia.org/wiki/U...temperature_processing

Interesting. I wonder how they do that. Seems like it would be difficult to heat a substance to 275 F° for 1-2 seconds. I suppose maybe they pass it through tubes that are highly heat conductive (e.g. copper tubing), and immersed in fluids of the proper temperature for the ultra fast temperature swings, or something similar.

 

[Siddhartha]

1. Food is sealed in a glass, metal, or plastic container.
2. Cooked in a large pressure cooker until commericially sterile.

Using preservatives, including salt, is not necessary.

 

[sao123]

Originally posted by: Siddhartha
1. Food is sealed in a glass, metal, or plastic container.
2. Cooked in a large pressure cooker until commericially sterile.

Using preservatives, including salt, is not necessary.

just because salt isnt necessary doesnt mean it isnt added... it wasnt until recently that makers of canned vegetables are now coming out with no/low salt cans.