| Melanins of black sesame is a kind of functional pigment that has high edible value. There are little research on the pigment. In order to solve the questions, this thesis deals with the extraction, isolation and purification of pigment from skin of black sesame, discussing some factors affecting pigment stability,. The theoretical foundations and the practical value of the melanins were provided for the development of the new food additives.Experiments show the best extraction condition of melanin from skin of black sesame was extraction melanin below 60℃for about 120 min with sodium hydroxide 5g/100g, and the extracting proportion of solid to solvent was 1:40 (w/v). Order of affecting factors involved with extracting efficiency could be sorted as time, proportion of solid to solvent, temperature,solvent concentration.A method for the preparation and purification of melanin from skin of black sesame was developed in this paper. After removing most associated impurity by acid washing with diluted hydrochloric acid and concentrate acid hydrolysis, sodium hydroxide was added in order to dissolve the melanin completely, then the melanin was precipitated by adding hydrochloric acid in order to change of PH in the solvent system. Finally , recrystallization was repeated for six times and refined melanin pigment was obtained. Besides , ultraviolet-visible and infrared(IR) spectra. The results revealed that the melanin is an irregular high-polymer mainly consisting of eumelanin structure.The melanin is soluble in water and alkaline solution, insoluble in organic agents. While the majority metal ions had no side-effect on pigment stability, only Fe3+,Cu2+,Zn2+ had a little influence. Heat–resistant, oxidize-resestant, and its light-resistancce and reducing-resistance is rather better. Oxidant agent , reducing agent and sugar agent has no obvious effect.The free radical scavenging capacity of melanin was investigated. The results showed melanin could scavenge the free radical (DPPH·,·OH,O2-·). The mechanism of antioxidative activity of melanin was discussed on the basis of melanin molecule structure. |
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