like in a store bought bolognaise sauce, how does the meat in it stay safe to eat? the ones where it has the part on the lid that u press to check it hasn’t been unsealed.
i love meat sauces but genuinely just curious about what happens to it that makes it able to be kept in a jar out of the fridge for months and it still being safe to eat?
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Part of canning food is making sure all of the bacteria is dead before sealing it up. That usually means boiling the jars and lids, pouring sauce in while it’s still hot.
That’s the reason why a can or jar that isn’t fully sealed should be discarded – on glass jars you have the center of the lid that pops up to let you know it’s not sealed anymore. That piece of the lid gets pulled down as the contents cool. On metal cans you just have to look for holes.
If they aren’t sealed, there’s a good chance bacteria got in and ruined your food.
Jarred and canned pasta sauces are pasteurized, which basically heats them hot enough to sterilize them, killing all bacteria inside of them. This means that as long as the jar or can isn’t damaged or opened, the stuff inside is bacteria-free and will last years in many cases – check the date.
Once you open that jar, you expose everything inside to the outside air, and there’s no guarantee that it’s bacteria-free any more. Which is why most of those jars will also say something like “consume within 7 days after opening” or something to that effect.
During the canning process (or jarring process) the meat is cooked in the can/jar.
Since it’s hot enough to kill off any bacteria or fungus and it’s sealed in thay state, more contaminates from the atmosphere can’t make it in. The food then cools down to room temperature. This cooling causes air and liquid in the can/jar to contract, which is how the safety seal stays down. Once the can/jar is opened, the pressure equalizes, and the safety seal pops out and outside contaminants have very likely made it in, even during the briefest opening.
The canning process cannot prevent rancidity, however, since that’s a chemical change in the food. It can slow it down if the food becomes rancid due to oxidation, due to a lack of oxygen. That’s why you don’t see canned milk, because it will still spoil.
Food spoils because of bacteria in it, and bacteria are killed by heat. So the jar is filled and sealed, and *then* heated to kill everything inside – while it’s already sealed! No living microbes inside = no food spoilage as long as the seal stays intact. This process is called Pasteurization, and was a HUGE revolution that changed life in developed countries.
What’s crazier is that you can do it at home if you have a pressure canner.
But only if you have a pressure canner – the temperature required to keep meat safe and bacteria free is a lot higher than acidic things (like pickles) or things very high in sugar (jam, jelly, syrup canned fruit). Low-acid canning requires higher temps only achieved with pressure.
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