| Because of the bright and stable color, good coloring effect, low cost and so on, the synthetic pigment play an important role in the market of edible pigment. People realize that it brings all sorts of threats to human health, so they’re getting lost on one side. Compared with synthetic pigment, natural pigment has so many characteristics. Such as wide range of sources, soft color, safe and non-toxic, the characteristics of a certain functional and so on. So people pay more and more attention to it. The research and development of natural pigment has become the main direction of the future development of edible pigment. Sorghum pigment is known well as a kind of flavonoid pigment. In fact, sorghum pigment is found as a mixture of several kinds of pigment in the production practice. In the course of the experiment, it is found that the Yellow sorghum pigment can be obtained by changing the method of extraction and settlement. In view of this phenomenon, carrying out further research about sorghum pigment. A yellow tone in the extract liquid causes people to think, A new natural yellow pigment can be developed. It can expand the variety of sorghum pigment.The subject research use the sorghum shell as the test material. In this paper, the extraction methods and stability of sorghum pigment were studied in detail. And the character and composition of sorghum pigment were analyzed preliminarily. This study provides a theoretical basis and reference for the development and application of sorghum pigment. The main conclusions are as follows:(1)The solvent method was used to extract the sorghum pigment in this test. The extraction effect of the high concentration of sodium hydroxide solution is the best by comparing the extraction effect of ten kinds of extraction solvent.So the 1% sodium hydroxide solution was determined to be the best extraction solvent.(2)Four factors was determined as the the influencing factors, including the concentration of sodium hydroxide, extraction time, extraction temperature, solid-liquid ratio. On the basis of single factor tests, the optimum extraction process of sorghum pigment was optimized by response surface methodology. The results showed that the sodium hydroxide concentration was 1.82%, the extraction duration was 4.25 h, the extraction temperature was 72.39℃, the solid/liquid ratio was 1:10. In order to facilitate the practical operation, the specific parameters are adjusted:the sodium hydroxide concentration was 1.8%, the extraction duration was 4.25 h, the extraction temperature was 72 ℃, the solid/liquid ratio was 1:10. Useing two times 95% ethanol to wash the extract after adjusting the parameters of the extraction, then dry the pigment sample.The yield of the product is 24.5%, the color value is 26.9.(3)The sorghum pigment obtained from this test is a kind of brown yellow powder, and it is a kind of water soluble pigment. Depending on the concentration, the color of the aqueous solution is changed from orange yellow to pale yellow.(4)The results of stability test show that:the pigment has certain stability to sugar, heat, sodium benzoate, K+ and Na+, and the low concentration of sugar, sodium benzoate, K+ and Na+ will have a hyperchromic effect on the pigment. Light, Ca2+, Pb+, potassium sorbate, hydrogen peroxide and sodium sulfite can influence the stability of the pigment, reducing its absorbance. The pigment is very sensitive to Fe3+, Fe2+, Al3+ and Cu2+, the presence of these ions causes the pigment solution to become turbid or the system becomes precipitated. Pigment loss of the original color effect. So the use and storage of the pigment should avoid contacting with such metal ions.(5)The pigment has a wide application range for pH. In the range of pH for 4-11, it can stabilize the performance of color. In the partial alkaline environment, it is better for the coloring effect; in the acidic environment, the absorbance of the pigment can be reduced.(6)There are three characteristic color reaction of flavonoids, as hydrochloric acid and magnesium reaction, ferric chloride reaction and neutral lead acetate reaction. The pigment solution remains yellow, and bubbles appear at the same time after adding magnesium powder and concentrated hydrochloric acid. This shows that the pigment contains phenolic hydroxyl, belong to flavonoids. The pigment solution adding 1% ferric chloride solution, the color becomes dark brown, that mains it contains phenolic hydroxyl. After adding saturated neutral lead acetate solution, the yellow precipitate was produced, then add glacial acetic acid, precipitation gradually dissolved.(7)The scanning pattern of aqueous solution of the pigment has an absorption peak at 280nm. Scanning spectrum of the pigment ethanol solution, at 280 nm has a very obvious absorption peak, at 325 nm with a shoulder, at 400 nm has an absorption peak. The scanning pattern of methanol solution of pigment has an absorption peak at 210nm and 280nm respectively. The UV-Vis scanning spectra of pigment were obtained by scanning the pigment aqueous solution, the pigment ethanol Solution and the pigment methanol solution. By analyzing the above results, the main components of the pigment were judged to be isoflavone, flavonone or dihydroflavonol. |
PDF Full Text Request