Physicochemical properties and antioxidant activities of Auricularia auricula melanin

The physicochemical properties and antioxidant activities of Auricularia auricula (A. auricula) melanin were studied. The result showed that A. auricula melanin powder was dark with a little red and yellow colored (L*=41.03, a*=2.26, b*=3.78) . The solubility properties of A. auricula melanin were very similar to those of the typical melanin. A. auricula melanin possessed a stronger thermal stability and pigment retention rate was 88.0% after heating at 100℃ for 4h. Whereas, A. auricula melanin was sensitive to light and pigment retention rate was only 25.3% when irradiation for 5d by natural light. A. auricula melanin exhibited a strong antioxidant activity. At concentration of 1.0mg/mL, hydroxyl radical scavenging activity and lipid peroxidation inhibiting activity of A. auricula melanin were greater than 40%. Thus, A. auricula melanin could be further used as a natural healthful food colorant.