To can tomatoes in Mason jars, first remove their cores and score their bases, then blanch in boiling water and shock in ice cold water. Next, discard the skins and seeds and crush the pulp into a pot to bring to a boil and simmer until broken down. Sterilize the jars by submerging in near-boiling water then fill with the tomatoes, seal the jars and lower into a pressure canner for 15 minutes before cooling.
To can tomatoes with Mason jars, follow the steps below.
- Prepare tomatoes
- Stew tomatoes
- Sterilize jars
- Can tomatoes
Cut the cores from the tomatoes and score the bottoms. Then, keeping a cooler of ice water to hand, place the tomatoes into a pot of boiling water for between 20 and 30 seconds before transferring to the ice water. Next, peel off the skins and remove the seeds to discard, mashing the flesh into a bowl.
Transfer the tomatoes to a cooking pot and bring to a low boil with water before reducing the heat to simmer.
Bring 3-quarts of water to at least 180 F in a pressure canner, then submerge the Mason jars, lids and other parts.
Remove the jars from the water and fill with the stewed tomatoes, leaving around half an inch at the top. Then disturb with a chopstick or spatula to eliminate air bubbles. Wipe the jars clean and seal. Place the jars into the canner and cover with the lid, maintaining a high heat and allowing steam to vent for 10 minutes before attaching the valve. When the pressure reaches 11 lbs., turn the heat down to a low setting and time for 15 minutes, aiming to remain at or above 11 pounds. If the pressure goes below 11 lbs., raise the temperature again and time for another 15 minutes. Finally, turn off the heat and allow the jars to cool until the pressure falls to zero. Remove the cans and cool. Test the canning by holding the jars by the lids to see if they give way. If so, the tomatoes will not keep for long.