I have a hard, white material like "fish scales" in my homemade ketchup. Is it safe to eat?
These white deposits are calcium nitrate and are commonly found in home canned pureed or mashed tomato products. They are considered safe to eat. This occurs due to the mashing or pureeing process. It is not known why this occurs, however these deposits seem to vary with growing seasons and geographic locations of the harvested tomatoes. The deposit is usually on the surface or attached to the side or the lid of the jar. Simply remove with a clean spoon. The texture of calcium nitrate distinguishes it from mold growth, as it is hard, like fish scales, and won't disintegrate when rolled between fingers.
Sources: MSU "Hot Lines," Oct/Nov
1982 "Hot Lines," 82-10,11 Food Features #6, June 1983
Last update: Tuesday, May 05, 2009