Copper sulphate

Copper(II) sulphate (cupric sulphate) is used in food at trace levels primarily for its role in preserving the green colour of processed vegetables. It forms stable copper-chlorophyll complexes that maintain a bright green colour in canned peas, herbs, and certain other preserved vegetables that would otherwise turn olive-brown during heat processing. It is also used in wine fining to remove hydrogen sulphide off-flavours.

JECFA's ADI is 0.5 mg per kilogram body weight per day expressed as copper, evaluated in 1965. This numerical ADI reflects that copper, while an essential mineral, is toxic in excess. At the trace concentrations used to maintain vegetable colour, dietary exposure is well below the ADI. The EU sets strict maximum residue limits for copper in food to ensure safety.

Copper sulphate is approved in the EU at restricted maximum use levels and in several other markets. It is found in commercially canned or preserved green vegetables where colour maintenance is important. For healthy adults at typical dietary exposures there are no safety concerns — dietary copper from all sources, including E519, remains within normal physiological ranges. Individuals with Wilson's disease (copper metabolism disorder) should monitor copper from all food sources.