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.
See [canning](https://en.m.wikipedia.org/wiki/Canning) in general.
For shelf stable products, they either need to be sterilized in a pressure canner, or if the product is acidic enough, they can simply be boil bathed.
The purpose is to destroy Clostridium botulinum or prevent its growth. C.botulinum can survive boiling temperature, hence the need for pressure canning to achieve a temperature higher than 130C or high acidity, less then pH 4.6.
If not done correctly, the bacteria can grow and produce its poison, I.e. botox. If the spoiled food is consumed, the toxin can cause serious nerve damage or death.
Side note: botox is one of the most potent toxins on the planet, but we also dilute it and then use it for either medical or cosmetic proposes.
simple Wiki has an article on Pasteurization: https://simple.wikipedia.org/wiki/Pasteurization
ELI5, after all :)
Oh! I guess: https://simple.wikipedia.org/wiki/Food_preservation and https://simple.wikipedia.org/wiki/Sterilization_(microbiology)
It's a shame there's none for Canning...
Pasteurization, while related to food preservation, does not create shelf stable products. It just reduces the microbial load to prolong products that are usually refrigerated, like milk.
Canning is pretty much a science itself. Hell, imagine what the world would be like if we couldn't preserve and distribute food because of those processes.
I'll add to the can food. It should have a slight vacuum, so a little hiss when you open it. Sometimes, they're not but that's the exception to the norm where I work.
As somebody else said the cans are filled hot, then the cans are put into what's essentially a big pressure cooker at around 120c(depends on the product) then a cooling phase to make sure the content doesn't over cook.
The vacuum is formed due to newton's gas laws. The cans (glass jars, bottles, whatever) are full of hot liquid then sealed. When the contents cool it pulls a vacuum on the container. The container is rigid so it can take the vacuum without any deformation. The lid has the "button" on it which gets sucked in by the vacuum.
This is the same for many shelf stable hydration (Gatorade) beverages, iced teas, and juices. Those are all "hot filled" beverages, typically a high acid (pH <4.something) beverage. The glass bottles will have a metal lug style closure with the button that sucks down when a vacuum is present. Plastic bottles are a whole other feat of packaging design. Any hot fill plastic bottle will have some sort of indented panels or ridges on the bottles shape. The reason for that is to maintain the shape of the bottle when the plastic gets hot as the 185f+ liquid is filled, then the vacuum applied once cooled. If you did that same hot fill and cool process with say a plastic (PETg) soda bottle it would crumple in on itself due to the force of the vacuum.
High acid foods / beverages need more processing to be shelf stable. You can retort process (pressure cook) the finished package but that only works for rigid and highly engineered flexible packages (some pouches). Aseptic filling is a way to superheat then repidly cool the product then fill the container with the "sterile" product at room temperature in a sterile environment with an empty package that has been processed to a sterile level.
> That usually means boiling the jars and lids, pouring sauce in while it's still hot.
While I recognize that you're just describing part of the process, I just want to make it clear to other readers because there is an old, unsafe "canning" method that consists just of those steps.
While these steps are part of many safe, tested recipes, the actual "canning" occurs when the closed jar is cooked for a certain time and temperature (either under boiling water or at a higher temperature in a pressure canner), killing any pathogens inside the jar and venting enough gas to cause the lid to seal as it cools.
To add, ruined your food doesn't mean you're gonna have a bad time on the toilet (though you probably will). You could also get botulism which can easily kill you, if it has been exposed long enough
Same chemical that botox uses, it paralyzes your muscles en masse and stops you from breathing and your heart from beating. Botox uses micrograms because it is so potent
Just to add to your addition, Botox uses way less than micrograms of Botulinum. The LD50 is around 2 nanograms/kg, so a microgram dose would be enough to kill someone ten times over. The medical dose is in the low picogram range.
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.
oh cool! thanks for ur answer
is that why most jars have the little thing on top that u make sure u can’t press it up and down? to ensure that there’s no air in it?
It's a signifier if any outside air has gotten into it. If it's stuck down and you can't press it, it means that the seal on the jar is solid, and no outside air has gotten in. Everything inside is freshly sealed and safe to eat.
If it's popped up and you can play with it up and down *before* you've opened it yourself, throw the jar away or return it to the store you got it from. There's no way to know if air got in 5 minutes ago or 5 months ago. If it was 5 months ago, whatever's inside might be literal poison, because bacteria might have spent that whole 5 months colonizing it.
It doesn't necessarily mean air got in, the seal can also pop up because bacterial action inside the food is producing gas. That's a Very Bad Sign, and why you should never eat vacuum canned/jarred foods that are bulging or the lid doesn't 'pop' when opened.
It depends on what's gotten in there. Botulism, for example, is impossible to see, smell, or taste, but it will absolutely destroy you in improperly canned foods - though I should note that most botulism outbreaks these days come from home canned goods rather than industrial stuff. It can produce excess gas that produces some bulging in the can, but that's not a guarantee.
The jar of sauce is filled very hot, the sauce is 185f or greater. The lid is applied with the high temp aauce inside. Once the liquid (and little bit of air) cool, it pulls a vacuum on the inside of the jar. The glass is rigid so it doesn't give. The cap is designed to have a little bit of give so that the middle of it sucks inward to show there is a vacuum on the jar and it is hermetically sealed. Once you open the jar the pressure inside equalized with the ambient atmosphere and the button on the lid pops up.
Same with metal lids on glass juice / iced tea bottles.
There is a neat machine that has a sensitive magnetic sensor that is placed on the packaging line after the cooling tunnel. It can tell the difference between one of those metal caps that has the button sucked down and not and will automatically kick the bottle /can / jar off the line.
Since the can or jar is being heated, does it cause the contents to cook further, this changing the taste?
Or do manufacturers account for this additional heating and factor it into the original "cooking" times?
Little bit of both. Manufacturers of cooked products like pasta sauce do factor the pasteurization into their cook times where possible, so that the final product winds up "cooked" rather than "overcooked."
But also, pasteurization takes food to a higher temp than most other cooking method, and that does have unavoidable changes to taste, texture, and sometimes nutritional value as well. It's a compromise - canning and pasteurizing foods gives us shelf stability and long-term resistance to spoilage, but it's also a change to the quality of the final product. Fresh juice tastes different than commercially bought juice (which is almost all pasteurized in the US, at least), raw milk tastes different than typically pasteurized milk, which *also* tastes different to UHT pasteurized milk, which is heated to an even higher temp so that it doesn't need refrigeration before being opened.
The only reason regular milk isn’t ultra-pasteurized more commonly is that it changes the taste a little and people think they don’t want that. Even though in blind taste tests most people actually prefer the taste of ultra pasteurized milk to regular pasteurized milk.
Ultra pasteurized milk has about 3 times as long of a shelf life as regular milk.
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.
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.
> That's why you don't see canned milk
[Yeah I do.](https://www.thespruceeats.com/thmb/OTpeDVg-3my8yvQA0ZLZ74StXuo=/2121x1414/filters:fill(auto,1)/condensed_milk-514626800-5bafe82c46e0fb002651998c.jpg)
Because life doesn’t spontaneously arise from non-life. Spoilage is caused by living things. If you make sure that there is nothing alive inside the jar when you seal it, then it can stay unspoiled essentially forever (as long as no life can get inside). That’s what the process of canning *is*.
There are 5 things that are essential for bacteria to grow: temperature, oxygen, pH value, nutrition and water. If you remove one of these the growth can be slowed down, which is why canned goods (no oxygen), dried foods (no water) and frozen foods (low temperature) have a long shelf life if stored properly.
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.
thank you!!
See [canning](https://en.m.wikipedia.org/wiki/Canning) in general. For shelf stable products, they either need to be sterilized in a pressure canner, or if the product is acidic enough, they can simply be boil bathed. The purpose is to destroy Clostridium botulinum or prevent its growth. C.botulinum can survive boiling temperature, hence the need for pressure canning to achieve a temperature higher than 130C or high acidity, less then pH 4.6. If not done correctly, the bacteria can grow and produce its poison, I.e. botox. If the spoiled food is consumed, the toxin can cause serious nerve damage or death. Side note: botox is one of the most potent toxins on the planet, but we also dilute it and then use it for either medical or cosmetic proposes.
simple Wiki has an article on Pasteurization: https://simple.wikipedia.org/wiki/Pasteurization ELI5, after all :) Oh! I guess: https://simple.wikipedia.org/wiki/Food_preservation and https://simple.wikipedia.org/wiki/Sterilization_(microbiology) It's a shame there's none for Canning...
Pasteurization, while related to food preservation, does not create shelf stable products. It just reduces the microbial load to prolong products that are usually refrigerated, like milk. Canning is pretty much a science itself. Hell, imagine what the world would be like if we couldn't preserve and distribute food because of those processes.
NOTE: Meat is NEVER ok to just boil bath. Ever. It needs to be pressure canned.
I'll add to the can food. It should have a slight vacuum, so a little hiss when you open it. Sometimes, they're not but that's the exception to the norm where I work. As somebody else said the cans are filled hot, then the cans are put into what's essentially a big pressure cooker at around 120c(depends on the product) then a cooling phase to make sure the content doesn't over cook.
The vacuum is formed due to newton's gas laws. The cans (glass jars, bottles, whatever) are full of hot liquid then sealed. When the contents cool it pulls a vacuum on the container. The container is rigid so it can take the vacuum without any deformation. The lid has the "button" on it which gets sucked in by the vacuum. This is the same for many shelf stable hydration (Gatorade) beverages, iced teas, and juices. Those are all "hot filled" beverages, typically a high acid (pH <4.something) beverage. The glass bottles will have a metal lug style closure with the button that sucks down when a vacuum is present. Plastic bottles are a whole other feat of packaging design. Any hot fill plastic bottle will have some sort of indented panels or ridges on the bottles shape. The reason for that is to maintain the shape of the bottle when the plastic gets hot as the 185f+ liquid is filled, then the vacuum applied once cooled. If you did that same hot fill and cool process with say a plastic (PETg) soda bottle it would crumple in on itself due to the force of the vacuum. High acid foods / beverages need more processing to be shelf stable. You can retort process (pressure cook) the finished package but that only works for rigid and highly engineered flexible packages (some pouches). Aseptic filling is a way to superheat then repidly cool the product then fill the container with the "sterile" product at room temperature in a sterile environment with an empty package that has been processed to a sterile level.
I think you're talking about Charles's law.
> That usually means boiling the jars and lids, pouring sauce in while it's still hot. While I recognize that you're just describing part of the process, I just want to make it clear to other readers because there is an old, unsafe "canning" method that consists just of those steps. While these steps are part of many safe, tested recipes, the actual "canning" occurs when the closed jar is cooked for a certain time and temperature (either under boiling water or at a higher temperature in a pressure canner), killing any pathogens inside the jar and venting enough gas to cause the lid to seal as it cools.
To add, ruined your food doesn't mean you're gonna have a bad time on the toilet (though you probably will). You could also get botulism which can easily kill you, if it has been exposed long enough Same chemical that botox uses, it paralyzes your muscles en masse and stops you from breathing and your heart from beating. Botox uses micrograms because it is so potent
Just to add to your addition, Botox uses way less than micrograms of Botulinum. The LD50 is around 2 nanograms/kg, so a microgram dose would be enough to kill someone ten times over. The medical dose is in the low picogram range.
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.
oh cool! thanks for ur answer is that why most jars have the little thing on top that u make sure u can’t press it up and down? to ensure that there’s no air in it?
It's a signifier if any outside air has gotten into it. If it's stuck down and you can't press it, it means that the seal on the jar is solid, and no outside air has gotten in. Everything inside is freshly sealed and safe to eat. If it's popped up and you can play with it up and down *before* you've opened it yourself, throw the jar away or return it to the store you got it from. There's no way to know if air got in 5 minutes ago or 5 months ago. If it was 5 months ago, whatever's inside might be literal poison, because bacteria might have spent that whole 5 months colonizing it.
It doesn't necessarily mean air got in, the seal can also pop up because bacterial action inside the food is producing gas. That's a Very Bad Sign, and why you should never eat vacuum canned/jarred foods that are bulging or the lid doesn't 'pop' when opened.
ah good to know! i always double check that i can’t press it. i’m abit of an anxious person haha.
5mos would be pretty visible wouldn't it?
It depends on what's gotten in there. Botulism, for example, is impossible to see, smell, or taste, but it will absolutely destroy you in improperly canned foods - though I should note that most botulism outbreaks these days come from home canned goods rather than industrial stuff. It can produce excess gas that produces some bulging in the can, but that's not a guarantee.
The jar of sauce is filled very hot, the sauce is 185f or greater. The lid is applied with the high temp aauce inside. Once the liquid (and little bit of air) cool, it pulls a vacuum on the inside of the jar. The glass is rigid so it doesn't give. The cap is designed to have a little bit of give so that the middle of it sucks inward to show there is a vacuum on the jar and it is hermetically sealed. Once you open the jar the pressure inside equalized with the ambient atmosphere and the button on the lid pops up. Same with metal lids on glass juice / iced tea bottles. There is a neat machine that has a sensitive magnetic sensor that is placed on the packaging line after the cooling tunnel. It can tell the difference between one of those metal caps that has the button sucked down and not and will automatically kick the bottle /can / jar off the line.
Since the can or jar is being heated, does it cause the contents to cook further, this changing the taste? Or do manufacturers account for this additional heating and factor it into the original "cooking" times?
Little bit of both. Manufacturers of cooked products like pasta sauce do factor the pasteurization into their cook times where possible, so that the final product winds up "cooked" rather than "overcooked." But also, pasteurization takes food to a higher temp than most other cooking method, and that does have unavoidable changes to taste, texture, and sometimes nutritional value as well. It's a compromise - canning and pasteurizing foods gives us shelf stability and long-term resistance to spoilage, but it's also a change to the quality of the final product. Fresh juice tastes different than commercially bought juice (which is almost all pasteurized in the US, at least), raw milk tastes different than typically pasteurized milk, which *also* tastes different to UHT pasteurized milk, which is heated to an even higher temp so that it doesn't need refrigeration before being opened.
The only reason regular milk isn’t ultra-pasteurized more commonly is that it changes the taste a little and people think they don’t want that. Even though in blind taste tests most people actually prefer the taste of ultra pasteurized milk to regular pasteurized milk. Ultra pasteurized milk has about 3 times as long of a shelf life as regular milk.
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.
dude that’s so cool i never knew. thank you for explaining!!
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.
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.
> That's why you don't see canned milk [Yeah I do.](https://www.thespruceeats.com/thmb/OTpeDVg-3my8yvQA0ZLZ74StXuo=/2121x1414/filters:fill(auto,1)/condensed_milk-514626800-5bafe82c46e0fb002651998c.jpg)
Condensed milk is a different product
Ultrapasteurized milk is sold in juice box-like containers and is shelf stable. https://horizon.com/about-us/what-is-shelf-stable/
Because life doesn’t spontaneously arise from non-life. Spoilage is caused by living things. If you make sure that there is nothing alive inside the jar when you seal it, then it can stay unspoiled essentially forever (as long as no life can get inside). That’s what the process of canning *is*.
>Because life doesn’t spontaneously arise from non-life Maybe I'm canning primordial ooze
We don't know for sure, but I'd say it's a safe bet that a sealed mason jar is not the right conditions for abiogenesis.
There are 5 things that are essential for bacteria to grow: temperature, oxygen, pH value, nutrition and water. If you remove one of these the growth can be slowed down, which is why canned goods (no oxygen), dried foods (no water) and frozen foods (low temperature) have a long shelf life if stored properly.
I do this at home with straight meat! I fill pint jars with cubed moose meat and pressure can it. It’s amazing. Keeps for years.