Instructables
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Canning is a quick way to preserve large quantities of food.
"We eat what we can and freeze what we can, and what we can't, we can" is a saying in my family.

The USDA Complete Guide to Home Canning is the bible of safe canning. If it's done right, canned food can still be safe to eat after 100 years.

Io demonstrates at "Fort Awesome" in Berkeley CA. Other illustrations are from the USDA
 
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Step 1: Why Canning?

Picture of Why Canning?
"Keep it hot, keep it cold, or don't keep it" is another saying in my family.
This chart from the USDA shows why this is good advice. The microorganisms that cause food to spoil don't live well at high and low temperatures.

Canning is a way to preserve food at room temperature. It works by cooking the food and containers at high temperatures to kill micro-organisms and sealing the jar so no new ones can enter.

Properly canned food is safe. Improperly canned food can cause Botulism poisoning from Clostridium Botulinum bacteria. The name comes from the Latin word for "sausage", "botula".(wpedia)
The spores of this bacterium are present nearly everywhere. They can survive some boiling. They thrive in an anaerobic environment such as a sealed can, producing a nerve toxin. They can't handle acidity below ph4.6, oxygen, or a wet temperature above 250f.
The keys to safe canning of food are PH, moisture content, cooking temperature, pressure, time, sterile procedures and proper sealing.

Step 2: Get Too Much Food

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Io's making kiwi fruit jam.
That's a good choice because kiwi fruit is acidic. Sour = acidity = low ph. Clostridium Botulinum bacteria spores can't survive in sour food. Here's the approximate ph of a variety of foods.

Canning a big quantity takes just as much time as canning a little bit. So make a lot.
Correction: Io says her recipe says not to double the recipe or make larger batches, or it won't set up properly. In that case make multiple batches!
Great explanation of canning and how it works (and when it doesn't). I'll pass this on to my canning-wary friends. Many thanks!
morgaash4 years ago
yummy, kiwifruit jam
Foaly74 years ago

This works for preserving whole tomatoes, doesn't it?

AzureEyes5 years ago
good 'ible. Would a pressure cooker/canner make the process go by any faster? I'm trying to justify buying one.
woody5585 years ago
Do you have to have a can that has the thing that will snap when you press it?
a mason jar?
Can I use a jelly jar? It doesn't snap down though.
yes, and no... when you heat stuff, it expands, if you fill your jar with cold 'stuff' and heat/boil it, the jar will explode (if it doesn't let out air) but if you fill it with boiling hot 'stuff', and heat/boil it then, you'll be fine Making sense?
My understanding is that the 'final boil' is to expand the small pocket of air in the jar with heat causing it to push out some. Once cooled the air contracts causing a vacuum inside the jar sucking the lid down tightly, creating a nice tight seal.
some jars may not let air out
Thanks
CMLion5 years ago
Canning USA.com has a lot of good information on canning--plus the reasons for sterilizing the whole thing in boiling water.
This is my favorite step of the process. this is a great way to preserve food and use wasted steam. Thank you ;)
joca685 years ago
boil the filled jars? Can you explain why? I've been making jam for ages, and pickes and so on, but I never did this step. Am I doing it all wrong?
Just as one more precautionary step. Better to give the whole thing one more chance to boil any potential little buggers straggling on their way to botulism heaven.
It's nice to see others keeping the old skills alive.
I thought boiling the lids (with the seals) wasn't recommended - it can melt the ring and cause it to not seal completely when further processed. Don't the instructions say to either dip the lids in water that was just boiling or just pour boiling water over them?
TimAnderson (author)  laura.prickett5 years ago
Definitely follow the directions that came with your lids.
Sandisk1duo5 years ago
very useful!
thepelton5 years ago
Like the POTUS said: Yes we can!
SinAmos5 years ago
Great work here. Very useful.:)
very informative. love the charts!
thepelton5 years ago
It appears that you have canned kiwifruit in one photo. Would you use the same times for Kiwifruit that you use for blackberries?
PKM5 years ago
Why? Because we can.
We can food almost every year since 2004, Pickles, lots of types of jam(kiwi is too expensive, is it pretty good?) pickles, tomatoes, tomato sauce, vegetables, all kinds, that canning funnel and lid magnet for picking them out of the water are really nice to use.
Very nice, my wife and I used to can, been too long.