Structural Characterization and Stability Evaluation of Melanin from Liquidambar formosana Hance Leaves: A Potential Natural Pigment for Food Applications

In this study, purified Liquidambar formosana Hance melanin (P-LHM) was structurally characterized and evaluated for stability. The yield of P-LHM was approximately 3.47%. Analytical results revealed P-LHM is a melanin-rich complex where eumelanin and pheomelanin polymers are intimately associated with specific flavonoids, phenolic acids, and terpenoids. The condensation molecular formula of P-LHM might be ([C24H29NO9]n). The stability evaluation showed that under specific conditions (natural light, darkness, pH = 7–11, 25–100 °C, Na+, Al3+, Fe2+ solution, and low concentrations of reducing agents), the retention rate of P-LHM was >90%. Given its excellent stability, LHM may be used as a new type of food ingredient in the processing of black-colored foods. Meanwhile, the rich phenolic compounds provide a theoretical basis for the development of functional colorants, enhancing the functional value of food colorants.