Extraction Of Yellow Pigment In Millet Straw And Research Of Its Physico-Chemical Property

Most pigments in cereals belong to carotenoids and anthocyanin, distributing in the straw stalk and fruit. In this experiment, it took the millet straw as raw material, to study the extraction of yellow pigment in millet straw by the solvent extraction and microwave-assisted solvent extraction method. And it compared the two methods of extracting to select the appropriate one. Through the single factor experiments, it investigated the influence of different factors on the extracting of yellow pigment in millet straw. Then it chose significantly influencing factors by factor screening test. After that, using the Box-Behnken response surface experimental design to determine the optimum process. Test results are as follows:1. The millet straw's yield of No.10 of Zhangza is high, its color is yellow and balanced. So No.10 of Zhangza is the ideal variety for extracting of yellow pigment in millet straw.2. The analysis of response surface shows that the optimum extracted conditions of solvent extraction are:78% ethanol (V/V), extraction temperature is 60?, solid-liquid ratio is 1: 40 (g:mL). Testing the experiment under this condition, the real measured value of absorbance is 0.623, closing to the predicted value, the error is 0.32%.3. As the response surface result of microwave-assisted solvent extraction shows, the optimum extracted conditions as follows:72% ethanol (V/V) as solvent, solid-liquid ratio is 1:20 (g:mL),320 W microwave processing 30s, extracting three times. The average absorbance of pigment extracting solution was 0.634, is similar to the predicted value(The relative error is 1.09%). Comparing the two extraction methods, the microwave-assisted solvent extraction method has a short time (the time is only 0.24% of solvent extraction), higher efficiency, and smaller dosage of solvent.4. The pigment has certain degree heat resistance (can tolerate 80?) and oxidation resistance. However, its photostability and reducing resistance is poor. The reductant-Na2SO3 has hyperchromic effect. The yellow pigment is suitable for using in neutral or alkalineconditions; It can be used jointly with cane sugar, sodium chloride and other food additives, but citric acid and natrium benzoicum. Cu2+ will damage the yellow pigmengt, different concentrations of Ca2+ and Fe3+ have different impacts on the yellow pigment. K+ and Mg2+ had no influence on the pigment.5. Results of UV absorption spectra and the visible color reaction tests show that, the composition of this pigment is similar to yellow pigment in millet, they both belong to carotenoids. The yellow pigment in millet straw has a-carotene-5,6-epoxide. This pigment is alcohol-soluble and strongly polar pigment, it belongs to alcohol-carotenoids. By the preliminary depuration and freeze drying, the yellow pigment crude extracts changed to fluffy, flocculent red brick powder, its color value is 61.4.