Maximum limits on levels
of addition of synthetic colours are imposed by many countries, but
the use of anthocyanin often has no numerical limit, and maximum
dose is simply that which is sufficient to give the desired colour
strength (Henry, 1992). However, colour stability of anthocyanins
depends on a number of factors such as the structure and
concentration of the anthocyanin, pH, temperature, oxygen and
presence of complexing agents such as phenols and metals