Asked September 16, 2015, 6:39 PM EDT
York County Pennsylvania
No, if the citric acid is being used to acidify a product for safety in canning, such as with tomatoes, this idea not supported by the science involved in home canning. When citric acid is used to adjust pH for safety in following a canning process, a specific amount of citric acid is required. Dried lemon powder is not pure citric acid and there would be no conversion to make, nor has this preparation of dried whole lemon ever been tested as an acidulant. The citric acid activity in all dried lemons would not be the same.
Even the amount of lemon juice required for acidifying tomatoes is different than the amount of citric acid, and furthermore, we recommend commercially bottled lemon juice over natural because it has a minimum standardized amount of citric acid. Natural lemon juices vary in their citric acid content for the same volume of juice.
I cannot think of home canning recommendations in our guidelines where citric acid is recommended for purposes other than pH or acidity adjustment for safety in canning. Therefore, what you want to do would not be an acceptable substitution where citric acid is included.