Approximately 15 to 20 quart jars are required to can a bushel of tomatoes. Variation in the quantity produced by one bushel results from differences in quality of the tomatoes. One bushel of tomatoes weighs about 53 pounds, but some of the tomatoes in the bushel might not be fit for human consumption.
To can tomatoes, a small batch of fresh tomatoes is washed and submerged in boiling water for about 30 seconds or until the skin begins to separate from the flesh of the fruit. The tomatoes are then transferred to an ice bath, which halts the cooking process and allows the tomatoes to be easily handled. The skin is then peeled away, the core removed and the remaining fruit and juice are strained into a quart jar.
Herbs, such as basil, thyme, oregano and rosemary, are often added to the jar. One to 2 tablespoons of lemon juice is added to the jar to raise the acidity of the tomatoes, making it safe to can the fruit. A few teaspoons of boiling water are then poured over the tomatoes, and any residue on the sides of the jar is wiped away. The jar is then tightened according to the manufacturer's instructions.
Finally, each filled jar is placed into boiling water for 40 to 45 minutes to seal the jar. The jar is completely sealed when the impression in the middle of the top of the jar holds when it is depressed.