Canning 101

Every summer growing up I would watch my mom put up several batches of fruit and jam from local produce. It was an exhausting process, but I don’t think we ever ate store-bought jam. Instead, we were able to enjoy delicious produce all year long because my mom knew how to can. As I entered my teenage years I started helping her more and developed a love (or obsession, depending who you ask) for canning myself.

Canning is a great skill to have, especially if you have access to produce (from neighbors or your own garden). It is not that hard to do and only requires a few pieces of equipment. I love it because we often get power-outages at our home due to wind, and while I worry about our frozen foods spoiling, I never have to worry about the jars of food I have preserved. I also love knowing exactly what is in my foods and being able to make healthy foods for my family with my home-grown produce.

All the colors of these canned goods will give us a rich and varied diet through the bleak winter months.

Canning comes in basically two flavors. There is regular water-bath canning, arguably the most common form, where jars are submerged in boiling water. There is pressure canning, where jars are placed in a pressurized vessel for a particular amount of pressure and time. (There is also freezer canning, but this does not produce jars that are shelf stable.)

Why choose one method over the other? It is not really a choice, it all depends on what you’re canning!

Fruits, fruit spreads, and pickled goods are suitable for water-bath canning. This method capitalizes on a few features for preserving the produce: acidity (generally in the form of vinegar or lemon juice) and heat. By heating the jars up to boiling temperature and adding an acid, enzymes and other microorganisms are killed. The heat creates a vacuum when the jars are removed from the bath and food is kept preserved for years.

Foods like vegetables in plain water (not pickled) and meats don’t have enough acid to be safely canned in a water-bath canner so they must be pressure canned to get to the appropriate temperature to make the foods safe. I am not as familiar with this method (despite my wonderful brother-in-law getting me a pressure canner as a wedding gift, but it’s something I’m going to look more into in the future. It’s important to have your pressure canner checked yearly to ensure the gauge is working correctly.

In water bath canning, the acidity of the food kills the microorganisms that can cause illness or spoilage, along with heat to remove oxygen and create a vacuum. For foods with low acidity, the temperature needed to kill these microorganisms CANNOT be achieved in a water bath canner, so a pressure canner must be used to make these foods safe. You can use a pressure canner to can both high and low acid foods, but water bath canning is exclusively for high acid foods.

It is critical when you’re canning for food preservation to follow the correct steps of a tested recipe. This is not the time or place to experiment. The National Center for Home Food Preservation has a great free guide that goes into more detail here. I myself only follow recipes from cookbooks produced by companies such as Ball. These have been tested for safety and they have a lot of other good information in them including troubleshooting issues.


How We Canned Our Tomatoes

This is meant to be a general overview of canning, please follow an approved recipe when canning your own produce.

As you may have read in one of my other posts, we had a delightful bumper crop of tomatoes this year. I planted these with canning in mind (nothing beats homemade chili from homegrown tomatoes in the winter!), so I picked two varieties of Roma tomatoes. These are known for being good sauce tomatoes with their great flavor and lower water content compared to other regular tomatoes.

When enough tomatoes were ripe, I enlisted my husband to help start canning them. We canned halved tomatoes and some tomato sauce.

Before prepping the food, I like to get my water bath started. Check jars for chips, cracks, or scratches on the rim. These will, at best, not seal and your food will spoil, and at worst, break in your canner getting glass everywhere. Toss any jars with these flaws (or at least relegate them to a non-canning task. I had a beautiful bluish jar with a faint scratch on the rim that wouldn’t seal and now it’s storing oats for my rabbits.) With hot water and dish soap, clean enough jars for the amount of produce you’ll be preserving (recipes typically have an estimate for you, I always add one extra just in case). Rinse the soap off of the jars and put them in the canner with ~1 inch of water over their rims. Bring this to a gentle boil for at least 10 minutes before starting to can your produce.

Also set a sauce pot of water on low heat for your lids. You don’t need to include the rings, but I find putting the lids in the rings helps keep them separated. This water shouldn’t boil, but be hot enough to get the rubber seal around the edge of the lids soft. Buy new lids every time, don’t reuse lids. Rings are fine to reuse.

For any recipe, make sure your produce is clean and free of blemishes or rotten pieces. Always wash your produce thoroughly before canning!

I had two recipes for canned tomatoes to try, one with the tomatoes in their own juices and one with water. I found, at least with my Roma tomatoes, that canning them in their own juices doesn’t work that well. They don’t have much juice to begin with, so you have to push pretty hard on them to get any fluid accumulated. Ultimately they were packed too tightly and lost fluid during the canning process.

So for the rest of them we went for tomatoes in water.

Our recipe indicated that 2-3 pounds of tomatoes would fit in a quart jar, so we weighed out 5 lbs of tomatoes at a time hoping to get 2 quarts.  We washed our tomatoes then cored them. We set a small pot of water to simmer on the stove and when it was hot, dropped a number of tomatoes in. After no more than 40 seconds (or as soon as we saw the first skin starting to split) we removed all of the tomatoes from the boiling water and put them in a cool ice bath. This stopped their cooking and sped up how quickly we could handle them. With this process, the skins slip right off.

We did 25 pounds of tomatoes this way. Once skinned, halving the tomatoes, removing their seeds, and putting them in a big sauce pot.

My little helper is always there to catch anything I drop… (this photo is actually of our tomato sauce adventure where the skins are strained out after cooking.)

By the way, save all of these scraps if you have chickens or pigs, they’ll love you for it!

After all 25 pounds of tomatoes were done (limited by the number of quart jars that fit in the canner), I added just enough water to cover the tomatoes. I then heated them up, simmering for 20 minutes.

You can raw pack or hot pack a lot of fruits and vegetables. While hot packing (heating up the produce before putting it in the jars) is annoying and sticky, it does make the finished product look nicer. The fruit won’t float to the top as much as it does when it’s raw packed. Just a preference thing.

When the tomatoes are ready, pull the jars out, draining the water in each jar into the sink. If you leave all of the water in the canner, it will overflow when the full jars are put back in. Set the jars on a clean towel on the counter. Add two tablespoons lemon juice to each quart jar (you can add salt too, I usually forego it since I’ll be adding salt to whatever dish they’re going into). Then add your tomatoes. I try to separate as much fluid as I can initially, getting only tomatoes in the jars, then adding water from the tomato pot back to the jars to get them to the right level. We’re looking for 1/2 inch head space here.

When all the tomatoes are packed, take a moist paper towel and wipe the rims of each jar. Take your time here, because one little speck of tomato will prevent the whole jar from sealing and that sucks. When the rims are all spotless, use your magnet wand to grab a lid, placing this on the jar, then a ring. When tightening the ring, only make it finger tight, don’t try to put muscle into it to seal it. It needs a little room to breathe out air while in the canner.

When all the jars are lidded and ringed, place them back in the water canner. You should have enough water to cover the jars by at least one inch, but if you’re short you can add back the hot water from the sauce pot that was holding your lids. Process as described in your recipe, for us it was 45 minutes of a rolling boil (start counting from when the water boils again, not when the jars are added!). Be aware that processing times change with altitude, so make sure you take that into account!

When the time’s up, turn the heat to the canner off and let the canner sit without its lid for five minutes before removing the jars. Take the jars out, keeping them level, and place them on a towel on the counter with at least 2 inches of space between jars. You should start hearing the “pings” of jars sealing soon. Don’t mess with them! I know it’s so tempting… All jars should seal, the button on top should be sucked in and not move if you push on it with a finger, within two hours. If any hold out, put them in the fridge to eat soon or reprocess as described in your canning book.

After 12-24 hours, you can remove the rings. Grab the jars by the edge of the lid and lift the jar off the counter an inch or so. If the lid stays intact, the jar is sealed well and can be labeled and stored. If the lid comes off the jar was not sealed well and should be put in the fridge to be eaten. Growing up we always left the rings on the jars with no issues, but a good point was made to me recently that if you take the rings off you can spot spoilage quicker. It also prevents the really sticky fruits from seizing the rings to the jars, if you didn’t clean them up after canning… like you should’ve…

First batch of quarts, I have at least twice this on my shelves now with at least 10 more pounds of tomatoes waiting for me to get my act together.

I label my jars pretty simply, with the year they were processed and what is in the jar. I can tell tomatoes from applesauce without a label, but sometimes it’s nice to know which batch something came from or if there’s added salt in one.

I place all of my sealed jars a cool dark pantry where they will keep for over a year. But there’s always more to can next year, so I try to make sure we eat everything through the winter!

Author: Kaya

Kaya Diem has been farming on some scale since 2007, from rabbits to radishes and sheep to squash, she hopes to someday be as self-sufficient as possible. Kaya graduated from Oregon State University in 2014 with an Animal Sciences degree. She lives in Seaside, OR with her husband, dog, and various farm critters on about 5 acres.

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