Study On Extraction, Purification And Stability Of Pigment From Buckwheat Hull

Natural pigments, on the safe and reliable side ,can gradually replace synthetic pigments and become the main food pigments. The pigment extracts from Buckwheat hull is a natural pigment, which can increase the kinds of natural pigment and crop economy.The buckwheat pigment was extracted by two methods of circumfluence and ultrasonic from buckwheat hull. For contrasting, ultrasonic extraction method could extract the pigment efficiency. Adopted resin to purify rude pigment .The stability of the pigment was discussed. Preliminary studied the ingredient of buckwheat pigment.The optimal circumfluence extraction conditions was as follow: particle sizes 80, 50% alcohol concentration, pH 1.0, ratios of solvent to material 60:1, extract two times and each time for 210 minutes with 90℃. Based on the experiment, the yield is 5.0%, the color value is 15.5. The optimal ultrasonic extraction conditions was as follow: particle sizes 80, 70% alcohol concentration, ratios of solvent to material 50:1, pH 1.0, extract two times and each time for 4 minutes. Based on the experiment, the yield is 4.69%, the color value isl7. Ultrasonic extraction's yield is less little than circumfluence extraction, but more color value and save plenty more time.The result of purification was as follows: NKA-9 is better than the other 5 resins. The optimal adsorption conditions showed that pigment concentration 0.844 (absorbency) , speedl.5mL/min, pH 4.0. The optimal desorption conditions showed that dosage 85mL, alcohol concentration 60 %, speed 4.0mL/min. Based on the experiment, the yield is 1.5%, the color value is 53.The result of studying on pigment stability showed that, the pigment was stable against to tight, temperature and some food addictives such as dextrose, sucrose, antiseptic, citric acid and so on. Reducing agent and oxidant had obvious influence on the pigment. The color of pigment was darken in alkaline condition, but in acidic condition the pH had little influence on. Some metal ions, such as K⁺,Na⁺,Ca²⁺,Mg²⁺,Cu²⁺,Zn²⁺had little influence on the stability of pigment, but other ions such as Fe³⁺,Al³⁺ destroy its stability. Infrared spectrum result showed that the buckwheat pigment included the following framework:＝C-OH,(?), C＝O;GC/MS authenticated 5primary ingredients, molecular formula as follows: C₂₀H₂₀C1OP, C₁₄H₂₆O, C₉H₈N₂O₂,C₁₆H₂₃NO,C₁₆H₃₀O.