Processed
Ferrous Sulfate Heptahydrate
A tier
Ferrous sulfate heptahydrate is the blue-green crystal most people picture as "iron sulfate"—about 20% elemental iron, cheap, bioavailable, and eager to stain and oxidise. Flour fortification and some supplements still use it. It tastes metallic if the dose is high and it can catalyse fat rancidity. It is not the dried (monohydrate) form, which is less messy in a premix. Keep it dry or it cakes into a rusty brick. Encapsulated iron exists because this crystal is honest about its faults. Use heptahydrate when the process is wet or the tradition is old; use dried or encapsulated when the food is delicate.
Track this ingredient
Characteristics
Preparations
Traits
History
Green vitriol (ferrous sulfate heptahydrate) was already a known iron salt in medicine and trade.
Wartime flour fortification used heptahydrate as a cheap, available iron.
Cereal chemists documented its staining and rancidity faults in dry mixes.
Heptahydrate remained the economy iron while dried and encapsulated grades took premium premixes.