If you cook sealed cans they won’t explode, but jars will?
Sorry, but I’m not getting that…
Seems to me, a sealed can will burst quite nicely when heat is applied.
My misspent youth taught me a few things, anyway…
I guess you’re talking about this? And I have to agree, that doesn’t seem to answer the question. I’ve seen my mom can food in glass jars many times, and it involves heating the closed jars to high temperatures to seal them and kill bacteria. And if you heat a can in a way that would break a bottle, you’ll make the can explode (seen this happen myself in a camp fire).
Basically, I don’t think that column answered that question.
Exactly. The campfire thing was just the experience I was referring to, by the way. heh. Didn’t even remember my mom’s canning habits, but that drives the point home, as well.
So I’m either not understanding or buying that particular column.
A glass jar will break due to a sudden temperature change, which a can will not.
I think the question is one of degree. The point of the original article is that artificially ripened black olives are preferentially presented in a light brine - one that is too weak to ensure the contents do not become subject to bacterial attack - especially botulism. So the product must be processed to a degree that destroys the bacteria without any assistence from chemical additives. This is more stringent than normal fruit preserving - which will typically use syrup, strong brine, or vinegar to aid the anti-bacterial action.
My father was an enthusiastic home fruit bottler. Peaches, apricots, plums, all in syrup and bottled. The bottles were heated to near boiling in a drum of water. That level of heat plus the syrup was enough to preserve the contents. As well, the heat expanded the air in the gap above the fruit in the bottle, this passed out past the seal in the lid. When the bottle cooled, air pressure acted to push the lid down tight on the seal, leaving a partial vacuum in the bottle.
This venting of the bottle is a crucial issue - since it means that the pressure in the bottle will be limited to some small increase over atmospheric, even if the bottle was somehow raised to over boiling point. So, either the technique of placing the bottles in, at most, boiling water, or the venting of the seal, limits the maximum temperature the contents will experience to close to 100 C. This isn’t enough to kill the botulisim spores in a weak brine.
To get high enough you need to increase the pressure. So a pressure bottling or canning system (basically a pressure cooker) which typically gets the contents to 121C.
On an industrial scale you need to have some sort of continuous and large batch processing system that can aply the heat and pressure - usually as steam. Different systems are used for different cases - and glassware seems to be usually done in a system that includes a water bath, and additional application of external pressure to maintian the integrity of the container. Cans can be processed with steam alone, and don’t need so much care. In particular they don’t need the all the extra pressure the bottles need. Just superheated steam will do.
The bottom line simply seems to be expense. Heat treating a bottled low acid fruit in weak brine needs more expensive processing equipment. Cans are easier. And when this process was first invented, cans were pretty much the main way such processing was done. Glass is much more recent. So there is now no reason why glass could not be used. But it will add expense.
Au contraire, mon frere. Modern canning was invented in 1810 by Frenchman Nicolas Appert, using glass jars:
By “this process” I was referring to the chemical ripeining of olives described in the original Staff Report. No desire to cast apsersions on the rich culinary heritage of the French. 