Forgetting lemon juice in tomato canning?

Lemon juice is important in tomato canning because it helps lower the acidity level so that the food can be safely canned in a boiling-water canner. Without added acid, the acidity of tomatoes falls in the range of pH=4.6-4.9, which is too high for safe boiling-water canning. If the food is not sufficiently acidic, bacteria that can't be destroyed by boiling may enter the jar from the air, creating bubbles and spoilage. Therefore, lemon juice or another type of acid is recommended for safe tomato canning.