When the tomatoes are producing in the garden, there's only a certain amount of ways to use them. That's why this tomato juice is perfect to save for later. Once canned, it will be a welcome sight on a cold winter evening when soups are in order!
Run the cored tomatoes through a juicer/sauce maker or food mill. For a thicker juice, run the discarded skins through a second time.
Once the tomatoes are juiced, bring the juice to a boil over medium heat. Continue to boil for 10 minutes. The juice can be cooked as long as desired to condense and cook off any excess water.
Once cooked, remove from the heat and pour into sterilized jars, leaving ½ inch headspace. Add the citric acid or bottled lemon juice to each jar. Fit with lids and rings prepared according to the manufacturer's instructions.
Place in a boiling water bath fitted with a rack to lift the jars off the bottom of the kettle. Return to a boil and process for 40 minutes. Adjust for elevation using the USDA recommendation.
After processing, remove from the water bath and cool at room temperature for 12 hours. Once cooled, remove the rings and check for a good seal. Store at room temperature.
If using bottled lemon juice instead of citric, use 2 tbsp per quart jar.