How To: Canning Tomatoes
Capture a taste of summer with this step-by-step tomato canning how-to.
Spoils of Summer
What better way to capture summer flavor than in a jar of robust, home-canned tomatoes? For best results, you'll want to choose a tomato variety with ample meat (plum and San Marzano are good choices) and you'll want them just ripe. Discard any bruised, overripe or extremely under-ripe fruit.
Core and Score
Using a small paring knife, cut out the tough core of each tomato, then score the bottom.
Headed for the Heat
Once coring and scoring is complete, the tomatoes are ready for blanching.
Blanch and shock tomatoes as follows: Set a large pot of water to boil; keep a cooler full of ice water nearby. Submerge the tomatoes in boiling water for 20 to 30 seconds, until the skins wrinkle and split. Remove them to the ice water. Depending on how many tomatoes you are processing, you may need several changes of ice water, as the hot tomatoes will quickly melt the ice.
Skin, Seed, Crush ... and Stew
After removing each tomato from the ice bath, peel it, then break open to remove seeds and liquid. (Do this over a sieve with a bowl beneath to retain the juice.) Finally, crush the tomatoes over a third pot, discarding any that are under-ripe and resistant to crushing. Place crushed tomatoes with water (or puree) in a large pot on the stove. Bring to a low boil and reduce heat. Simmer the crushed tomatoes until they break down.
Keep it Clean
A lid caddy is a handy tool for sterilizing lids and rings and for keeping them off non-sterile surfaces.
Let the Canning Begin
Stuff a sprig of basil into each sterilized jar, if desired. Ladle the tomatoes through the wide-mouth funnel into each jar, leaving about 1/2" headroom at the top. Insert a clean spatula, knife or chopstick, and "bubble" the contents, wiggling it around the perimeter to dislodge any air bubbles. Using a wet paper towel, wipe the rims of the jars clean, then set the lids on top. Screw on rings until just finger-tight.
Timing is Everything
After each batch of jars has been filled, placed in the canner over high heat and vented for 10 minutes, apply the canner valve. Keep the canner over high heat, monitoring the pressure. When the pressure hits 11 pounds, reduce the heat to low and set the timer for 15 minutes. Keep an eye on the pressure: It can go over 11 pounds, but it's best to keep the pressure as stable as possible. Moreover, if it dips below 11 pounds, it must be brought back up, and the 15 minutes started again.
After the jars have completely cooled, test the seals by removing the rings and lifting each jar by its lid. If the lid gives, the seal did not set. These jars may be refrigerated and used right away, or the tomatoes can be reprocessed and canned, repeating all previous steps.
150 Degrees of Separation
As the contents of the jars cool, some separation may occur. This is normal and somewhat more likely with tomato water; puree tends to retain its emulsion better.
See more: 101 Ways to Love Summer