Easy, step by step instructions for how to can tomatoes; including supplies, how to fill the jars, canning equipment, and why can tomatoes.
If you’ve ever canned anything, you know exactly what I’m talking about. After all the prepping food, filling jars, carefully lowering into the water and trying not to get burned getting the jars out, while they’re sitting on the counter, you start to hear:
It’s the sound of something done right, of a process accomplished. You breathe a sigh of relief and listen joyfully.
The jars are sealing.
I’d never canned a thing until last summer, when I jumped in and did pickles and salsa based almost entirely on verbal instructions from friends at my book club along with their quickly written recipes. It was a bit cheeky not to read up more on the process, I suppose, and I was deadly nervous about the whole thing, but that POP was the best sound ever at the end. I knew I had done it more or less correctly, and it felt great.
My grandmother and I then did a half bushel of tomatoes, and I picked up some more good tips. If you’re a beginner in the world of canning, this post is for you. (Come back tomorrow for the best salsa recipe I’ve ever had if you already know what you’re doing!)
How to Can Tomatoes
Let me start by saying that you shouldn’t “take my word for it.” Be sure to check out some more comprehensive sites. I’ve learned a lot from http://canningjarsetc.blogspot.com/. Most people recommend just getting the Ball Complete Book of Home Preserving, but I’m pretty cheap.
First, you gather all your supplies the night before. You’ll need canning jars, lids, and rings. Inspect the tops of the jars for cracks. (Confession: I reuse lids, even though you’re totally not supposed to. That’s so bad! I check them for issues and make the call. If they don’t seal, I’ll put the jar in the fridge and use it soon. If they unseal, I cut my losses.) Run the jars and rings through the dishwasher on high heat to sterilize, preferably ending the cycle right about the time you need them so they’re still warm (easier said than done in a household with children).
Pardon the blurry photos in this post; my canning time is usually after the kids are in bed, and the lighting is not exactly ideal for photography!
Before you even start with the food preparation, get the pots ready on the stove. Fill your canner (I just have a water bath canner that I inherited from my great aunt) about 2/3-3/4 of the way with water, depending on the size of your jars. You’ll want the water to cover the submerged jars by about an inch. Turn that on high to get it boiling (lid on!). Put your lids in a small pot and bring it to a simmer, not a boil. Leave a spot at the front of the stove for your pot of tomatoes.
Note: Did you know regular canning lids are lined with BPA-laden plastic? If you’re looking for an alternative, try Tattler reusable, BPA-free lids.
Now you’re ready to start prepping tomatoes! I like to skin them, because sometimes the skins are harder to digest (at least according to Grandma). Do this by getting some water boiling – in the pot you’re going to use to cook tomatoes, if you want to save a pot – and put 5-10 washed tomatoes in for one minute or so. Take them out with a slotted spoon and put them in a colander where you’ll run cold water over them. The skins just slip right off with a paring knife or even just your fingers.
I think that part is so cool, almost like magic! My next step was to core the tomatoes, which is really simple with a paring knife or even just your fingers.
Next, you can dice them and put the pieces in a big pot to cook/simmer. My grandma doesn’t use a cutting board but rather just hacks the tomatoes apart in midair over the pot with a paring knife, like you might when slicing an apple or peach. The size and shape of the tomatoes matters little after they’re cooked.
Get ’em boiling on the stove. Your canning pot water should be totally ready by now; in fact, you probably have had to turn it to low and make it wait for you. That’s okay. Better it waiting than you, especially if bedtime is approaching.
To expedite the process, you can fill the first set of jars as soon as you have enough tomatoes ready for them, then continue to chop tomatoes into the pot as round one processes in the canner. (Process is the canning word for boiling the jars for the appropriate amount of time for them to seal.)
How to Fill the Jars
This is the part where my heart starts racing a little bit. Up until this point, you can be interrupted by kids, the phone or even dinner, but for about 10 minutes here, it would be best if you were focused (Hence the 10 p.m – midnight canning at my house). Prepare the following supplies on the counter near your canner:
- tongs or magnet thingy to get lids out
- clean, dry washcloth
- 1/2 or 1 tsp. measuring spoon
- salt in a little dish
- oven mitt (to move the warm jars once filled)
You’ll need to:
- Fill a jar of tomatoes using a ladle, and optionally, a canning funnel. Best practice is to use hot jars, so right out of the dishwasher is great.
- Add 1/2 tsp. of salt per pint, 1 tsp. per quart, preferably coarse or kosher salt. I used Celtic. If you’re a forgetful person like me, you may want to put the salt and acid (below) in the jars first, all at once. With quarts, I added 1/2 tsp. at the bottom of the jar and 1/2 tsp. at the top.
- Add 1 Tbs. lemon juice or 1/4 tsp. citric acid per pint (double for quarts). This is necessary because so many tomatoes are “low-acid” these days. My grandma didn’t use to have to add the acid, and we actually forgot when we canned last summer, but it’s probably not a rule I should take so lightly.
- Wipe the rim of the jar with a clean cloth.
- Pull a warm lid out of the simmering pot and place it on the jar, then tighten the ring (but not as tightly as you possibly can, just a quarter turn or so past “on”).
- Get the jars into the canner, balancing them on the rack. Put them in as you fill them, and you want to get them all in quickly so you can get the jars processing as soon as possible. Keeping everything hot is important.
- Lower the jars, make sure the water is about an inch over the tops of the jars (i.e. the jars are totally submerged plus some), put the lid on the canner and bring to a boil.
Now the kids can bug you if they need something. 🙂
The boil will take longer than you think. Do not start your timer until you have a genuine, rolling boil. Process for 10 minutes 40 minutes for pints, 45 for quarts, then lift the rack and hang it on the canner. See here for details. I didn’t process long enough. That’s what I get for learning from grandma with an old, old recipe, from when canning didn’t have federal recommendations and probably wasn’t so safe. Sigh. See comments for more. Use a really good oven mitt or the jar lifters from your canning equipment to get the jars out, setting them on a towel spread out on your counter. I prefer the Ove’ Glove for jobs like this, since I never invested in the right equipment. This is 21 pints of diced tomatoes, a half bushel’s worth, which costs about $9-10 at my farmer’s market.
Now is the fun part. Pop! Pop! Pop! Within an hour, and often in the first 5-10 minutes, the jars will begin to seal. Write the year on the top and let them cool, and you’ve got food for the winter (just like Blueberries for Sal).
Speaking of equipment…my “canner” is actually just a gigantic pot that looks exactly like a canner, but with a flatter bottom. It’s what I make my chicken stock in and is sold for cooking corn, lobsters, etc. but looks a lot like this. I got the rack from my great aunt, and I didn’t even know it could hang on the side the first year. I hefted the entire rack, full of jars and pickles, from the stove across the kitchen to the counter. I wondered how my tiny great aunt managed to can when it took such strength! More brawn than brain, that night.
You can get by without most of the canning equipment: just use tongs to get the lids out of the pan, ladle carefully into jars and wipe the rims, and lift with mitts. I did invest in a canning funnel this year and wonder why I waited so long.
If you want to can anything other than fruits, salsa, and tomatoes (i.e., meat, beans, green beans, other vegetables) you need a pressure canner. Rene recommends this one as the safest and best out there.
The Big Question: Why Can Tomatoes?
Is canning tomatoes nutritious? In the traditional foods world, it seems that canning gets a bad reputation. For most vegetables and all fruits, heating does reduce the nutrients and high temperature/pressure often renders the produce far less nutritious than fresh or frozen. Tomatoes, however, release their lycopene when heated, and I’m going to buy canned tomatoes if I don’t make my own.
Does it save money? After the cost of the jars, new lids each year, and tomatoes, not to mention the energy used for the stove, canned tomatoes are pretty close to the same price as a good deal at the store. This was incredibly disheartening to me last summer after spending 4-6 hours canning tomatoes, then realizing I probably saved all of 50 cents! I vowed never to can again, unless by some chance I had a tomato harvest from my own garden. That would be worth it.
Other Health Benefits As the year wore on, however, I came across articles like this one called “7 Foods Even Experts Won’t Eat” and became more convinced that using the glass jars simply to avoid BPA might be reason enough. Compared to organic tomatoes in glass jars, I save half or more doing my own. Today at the Farmer’s Market, I found an entire half bushel basket of gorgeous organic tomatoes for 8 bucks. Hence, I will be canning twice as many tomatoes this year as last. Figures.
Have you seen 10 Questions to Ask Your Farmer? A helpful list for Farmer’s Market visits!
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