sprinklefingers

welcome to canning season at sprinklefingers!

today we’ll be discussing one of the key components to successful canning - the vacuum seal.

canning & preserving & jamming is all very fun. and rewarding. but the single most rewarding part for me? when my jars have sealed. a sealed jar means you can actually leave the jar (and whatever’s inside) in your pantry and not your refrigerator*. a good seal is what makes canning canning.

when you think about it, especially when making jam, you’ve put a ton of work into making something delicious and (in theory) long-lasting. to put that much work into something and then have the jars not seal (or even 1 or 2 of them not seal) is majorly disappointing to me. [again, this establishes that i don’t get out a lot.]

back to canning. what’s so important about the seal? especially to those of you new to canning? how do you get jars to seal? what if they don’t seal? seal, seal, seal! arf!

here’s the thing. let’s pretend we’re making jam.
once you’ve cooked the fruit, you basically immediately ladle it into the jars. the cooked fruit is hot, the jars (in theory) should be hot. you’ve got a giant pot of boiling water that is …. hot. once you ladle the cooked fruit into the jars, you place the metal lids on top, and screw on the screw bands. you then place these jars into the boiling water. and here’s where the magic happens:

air is pushed out of the jars, everything inside of the jars gets even hotter. once the air is gone and the jam inside the jars has reached a certain temperature, you’ve eliminated two of the biggest villains that lead to spoilage: air & bacteria.

once the jars are removed from the boiling water, they are set aside (undisturbed!) to cool. as the jam cools, the lids are squeezed down on top of the jars even tighter - it’s basically vacuum sealing itself - making it impossible for air to get in…which leads to long-lasting, spoilage-free jam. magic! incredible!

this ‘vacuum-seal’ process is key in anything you can, jam or preserve. you always, always want your jars to seal…and if they don’t you *sometimes are able to re-process them, but usually you end up just having to store whatever you’ve just gone to the trouble of canning in the fridge. not ideal when you set out to can something to begin with. also not ideal when fridge space is limited.

now that we’ve established how important a good seal is, tomorrow we’ll try out our first preserved fruit recipe. exciting!

in the meantime, here’s some more in-depth information on creating a vacuum seal while canning.