What it does
The colour comes from carminic acid, which is far more resistant to heat, light and oxygen than plant derived reds such as beetroot or anthocyanin. Its shade shifts with pH, from orange in acid to blue red at neutral, and it is usually supplied as an aluminium lake to fix the shade and improve dispersion.
Where it works
Meat products, where a stable red has to survive cooking and shelf life. Confectionery and dairy, where plant reds fade. Anywhere a beetroot red would brown within days.
Where it does not
It is of animal origin, which excludes vegan, vegetarian and several religious positionings, and that single fact is usually what decides against it regardless of performance. It can cause allergic reactions and must be declared by name in some markets. It also faces consumer resistance where the source is known.
What it interacts with
pH, which moves the shade. Protein, onto which it binds, which both stabilises it and changes the final colour.
