Chlorophylls (E140) are extracted from plant material using solvents. Manufacturers typically start with green biomass such as alfalfa (lucerne), grass, nettles, or spinach, which is dried and treated with a solvent like acetone, ethanol, or a hydrocarbon to dissolve the pigment out of the plant tissue. The solvent is then removed, leaving a concentrated green extract.
Natural chlorophyll carries a magnesium ion at the center of its molecule, but this bond is fragile. Under heat or acidic conditions the magnesium is displaced and the color shifts toward a dull olive or brown, while exposure to light gradually fades the pigment as well. To make a colorant that survives food processing and shelf life, producers replace the magnesium with copper, yielding copper complexes of chlorophyll (part of E141). This copper-stabilized form holds a brighter, more consistent green.
Both the plant extraction and the copper substitution are chemical processes applied to plant-derived starting material. No animal-derived inputs are involved in standard manufacture, which is why both E140 and E141 are classified as vegan.