Introduction: How to Can

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

Step 1: 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

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!

Step 3: The Importance of "PH"

This chart from the USDA Shows the ph of common foods. Botulism is prevented at a ph of 4.7 or below (acidic).
Acidic foods can be canned at boiling water temperatures.
Low-acid foods must either be pressure-canned, or acid must be added to lower the ph. Citric acid
(lemon juice), ascorbic acid (vitamin C), acetic acid or lactic acid vinegars are good choices of food acids that can lower the ph of the food.

Step 4: Cook It

Boil the stuff for 3 to 5 minutes.
Chant "Boil that dust speck! Boil that dust speck!" just like in the book "Horton Hears a Who" by Dr. Seuss, 1954.

Step 5: You'll Have Company

Now everyone will come and start cooking stuff, just to join in the fun. Nathan's making cookies for his co-workers at a major corporation. It takes a lot of butter to make that many cookies.

Step 6: Sterilize the Jars and Lids

Get like Butterfly McQueen and boil water in the biggest pots you have. You're going to sterilize everything. Start with the jars and lids.
When you get them they're clean but not sterile. Make sure they're fully submerged under the water. Boil them for 10 minutes if you're at sea level, and one minute for each 1000 feet of elevation above sea level.

Step 7: Altitude and Boiling Temperature

If you're at the top of Mt.Everest water boils at 156 F(wpedia) due to the very low atmospheric pressure there.
You'll definitely need a pressure canner to get your water hot enough to sterilize your jars.

Step 8: Fill the Jars

Ladle the hot goodness into the jars.
If any gets on the lip of the jar wipe it off carefully so the lid will seal well.
Leave a little bit of an air gap at the top.
When the air cools off later, it will contract making a vacuum.
That will make the lid go "ping" and suck inward.

Later on when you open the jar, you'll check that the lid is still sucked down. When you open the lid, hear the air suck in as the lid pings up. That's the sound safe canned food makes.
If that doesn't happen it means it wasn't sealed properly. Be afraid.
If the lid is bulged up, you're in trouble.
You've maybe got a witch's brew of festering botulism in there. Throw it away.

Step 9: Ladles and Funnels

If you have one of these swank funnels that fits your jars, your life just got easier. It makes it a lot harder to spill food on the lip of the jar. "Head space" is the air gap at the top of the jar. The USDA says the "hot packing" method shown here is better because it removes more air from the food.

Step 10: Boil the Filled Jars

Use the tongs to put the jars into the boiling water. Make sure they are covered by water. The water will stop boiling. Wait for it to boil again.
Boil them for the right number of minutes.
What is the right number of minutes? Refer to the USDA manual or a trustworthy recipe. Usually it's 15 or 30 minutes.

VA ag extension recommends these boil times:
Processing Times For High-Acid Foods Using A Boiling Water Bath Canner (212° F):
Fruits & Vegetables Pints Quarts
Apples (hot pack)*** 20 minutes 20 minutes
Apricots (raw pack)*** 25 30
Berries (raw pack) 15 20
Cherries (raw pack) 20 25
Dill Pickles (raw pack) 10 15
Sweet Pickles (raw pack) 10 15
Fruit Juices (hot pack) 15 15
Fruit Jams and Jellies 10 10
Peaches (hot pack) 20 25
Pears (hot pack) 20 25
Plums (hot pack) 20 25
Pickle Relish (hot pack) 10 --
Rhubarb (hot pack) 10 10
Tomatoes (hot pack)**** 35 45
Tomato Juice (hot pack)**** 35 40

Step 11: Canned!

Tong the boiled jars out of the pot and put them in your basement along with the guns, shovels, and rice. You're ready for the next disaster.

For more details about canning technique, read the rest of the USDA Manual

Comments

author
garnishrecipes (author)2012-07-16

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!

author
morgaash (author)2010-06-05

yummy, kiwifruit jam

author
Foaly7 (author)2010-04-16

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

author
AzureEyes (author)2009-09-19

good 'ible. Would a pressure cooker/canner make the process go by any faster? I'm trying to justify buying one.

author
woody558 (author)2009-04-18

Do you have to have a can that has the thing that will snap when you press it?

author
Sandisk1duo (author)woody5582009-04-18

a mason jar?

author
woody558 (author)Sandisk1duo2009-04-18

Can I use a jelly jar? It doesn't snap down though.

author
Sandisk1duo (author)woody5582009-04-18

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?

author
vikingbrute (author)Sandisk1duo2009-06-24

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.

author
Sandisk1duo (author)vikingbrute2009-06-24

some jars may not let air out

author
woody558 (author)Sandisk1duo2009-04-19

Thanks

author
CMLion (author)2009-06-18

Canning USA.com has a lot of good information on canning--plus the reasons for sterilizing the whole thing in boiling water.

author
Savethetrees411 (author)2009-05-11

This is my favorite step of the process. this is a great way to preserve food and use wasted steam. Thank you ;)

author
joca68 (author)2009-04-23

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?

author
carpespasm (author)joca682009-04-30

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.

author
poppamoon (author)joca682009-04-26

It's nice to see others keeping the old skills alive.

author
laura.prickett (author)2009-04-18

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?

author

Definitely follow the directions that came with your lids.

author
Sandisk1duo (author)2009-04-18

very useful!

author
thepelton (author)2009-04-18

Like the POTUS said: Yes we can!

author
SinAmos (author)2009-04-18

Great work here. Very useful.:)

author
captain Jack (author)2009-04-17

very informative. love the charts!

author
thepelton (author)2009-04-17

It appears that you have canned kiwifruit in one photo. Would you use the same times for Kiwifruit that you use for blackberries?

author
PKM (author)2009-04-17

Why? Because we can.

author
Yerboogieman (author)2009-04-16

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.

author
Tool Using Animal (author)2009-04-16

Very nice, my wife and I used to can, been too long.

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Bio: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of www.zcorp.com, manufacturers of "3D Printer" output ... More »
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