Study on Stability of Purple Pigment from Peristrophe roxburghiana

Purple pigment was extracted by ethanol extraction method from Peristrophe roxburghiana and used to study its stability.The results showed that the purple pigment of Peristrophe roxburghian had high light and heat resistance.It was stable when pH 5～13;unstable under strong acid and alkali conditions.Oxidant might cause decolorization of purple pigment;while reductant had protective effect of purple pigment.Food additive sucrose and potassium sorbate acid had little impact on the stability of purple pigment;while citric acid and vitamin C could react with purple pigment or cause its degradation.The effect of Na+,Zn2+,K+,Mg2+ and Ca2+ on the pigment stability and color was insignificant;however,Cu2+,Al3+ and Fe3+ could change the color of purple pigment and decrease its A580 nm.