Canning tomatoes is like storing a little bit of summer and getting to open it up again when the ground is covered in snow. It is also pretty easy to do. As long as you have a large pot, some mason jars, and lots of tomatoes... you can do water bath canning. Tomatoes are high enough in acidity that it doesn't require being canned in a pressure cooker. There are only a handful of things you can can this way, and even with high acidity, you still need to be careful and follow every step. You're not putting the preservatives and additives that food producers use in their canning process. So follow the steps and make sure your kitchen is nice and clean before starting!
1. After cleaning your kitchen, fill your large canning pot with water and heat it up to a rolling boil. This will take some time because of the volume of water. In a separate pot (normal size), fill with water and bring to a simmer.
2. While the pots are warming up, wash your tomatoes in the sink; one part vinegar to 10 parts water. Make sure any dirt is scrubbed off and the tomatoes can sit in the vinegar wash until you need them.
3. Once the water is simmering, cut an X into the skin of each tomato. This helps the skin peel away. Put several of the tomatoes in the simmering pot for about one or two minutes or until the skin starts pulling away from the X. Remove tomatoes from pot and dunk them in very cold water (I spray them with cold water in the sink). The skins should pull away easily and cool the tomatoes enough to be handled.
4. Once water in boiling in the large canning pot, put your clean, empty mason jars in the pot. This will help sterilize the jars. Always add one or two extra mason jars than you think you will use... it is always better to have too many than not enough! Leave the jars in the boiling water for at least five minutes. Then remove and set on towel.
5. Peel away skins from each tomato and cut out the core. Remove any blemished area completely. If a tomato smells funny, get rid of it... better safe than sorry. You can try to remove seeds at this point, but it can get really messy and you end up removing a lot of the juices.
6. Cut any large tomatoes into manageable pieces. Add tomatoes to sterilized jars and make sure everything is packed tight by pressing the tomatoes down into the jar with a spoon or spatula. Add about one teaspoon of freshly squeezed lemon juice to each jar to add some additional acidity.
7. Toss jar lids into boiling water to get the wax tacky. Wipe clean the tops of each jar making sure there is no residue anywhere around the lid area. Remove lids from pot and place them on top of the jars. Use the canning rings to secure the lids in place... screw on tight, then loosen about one centimeter to allow air to escape while in water bath but prevent the lid from coming off.
8. Carefully lower each jar into the canning pot. About 7-8 pint jars or 6 quart jars will fit at one time. The jars should not be touching each other. The water should be at least one inch above the jar lids when all jars are in the pot. Add hot water to pot if there isn't enough coverage. Once water has returned to a rolling boil, cover with lid and start the timer for 25 minutes.
9. After 25 minutes, check to see if you can see any bubbles coming out of the jars. After checking for about 30 seconds, if you haven't seen any bubbles, remove the jars from the pot and set on a towel. The lids will begin to "click" as the jars seal. If you saw bubbles coming from the jars, return the lid and continue to boil for another 5 minutes. Check for bubbles again.
10. After all of your jars have "clicked" shut and cooled down, remove the rings. Press on the center of the lid to make sure the jar sealed shut. If the lids still presses down and clicks, then the jar has not sealed, continue to wait. Some jars could take a couple hours to seal. Mine usually take between 30 seconds and 25 minutes. If your lid does not seal, it is not safe to store in the pantry. Keep it in the fridge for up to five days. Label all of your lids with the date.
You're done! You have successfully saved some of your summer harvest for another time. Toss out any canned tomatoes that have been stored for a year or longer.