Comparative Study on Purification Effect of Melanin in Pepper (Zanthoxylum bungeanum) Seed Coat by Different Treatment Methods
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Abstract:
Pepper seeds was used as raw material to prepare crude melanin extract of pepper seed coat (MCEP) by alkali-soluble acid precipitation method, and the MCEP was purified by hydrochloric acid hydrolysis, enzymatic hydrolysis, organic solvent extraction and alkali-soluble acid precipitation method, respectively, to obtain melanins of pepper seed coat (MP), which were labeled as SMP, EMP, OMP and AMP, respectively. The purification effects of the four treatment methods on MP were analyzed by the color of the pigment, ultraviolet-visible spectroscopy, color value, Infrared spectroscopy and its microstructure. The results showed that the L*, a* and b* values of SMP were significantly lower than those of AMP, OMP and MCEP (p<0.05), and the SMP was black amorphous powder with metallic luster; The SMP, EMP, OMP and AMP had maximum absorption at peak 220 nm; the color values of SMP, EMP, OMP and AMP were significantly higher than the color value of MCEP (151.25 U/g) (p<0.05), and the SMP color value (341.73 U/g) was the highest; Except for AMP, the infrared spectroscopy of OMP, EMP and SMP were weakened or disappeared compared with the absorption peaks of MCEP in C-H and C-H2 characteristic absorption band; The results of scanning electron microscope showed that SMP had a random block structure, and no other structural shapes existed. Therefore, we suggest that the hydrochloric acid hydrolysis is the best treatment method for purification and preparation of MP.
