Research On Extraction Conditions And Purification And Properties Of The Roselle Calyx Red Pigment

The roselle red pigment is a natural edible pigment, which has natural colors, non-toxic and harmless, it also has the effect of antioxidant and anti-tumor. It is a perfect combination of the coloring agent and antioxidants. And it becomes a new food additive which has great potential development.Roselle is a native plant of Africa and other tropical regions, gradually introduced into China in recent years, and grown in Fujian, Jiangxi and other areas. Roselle has detoxification, lowering blood pressure and blood fat, beauty and other effects. Roselle calyx is rich in anthocyanins, which is a ideal raw material to produce the Roselle red pigment.In this paper, the extraction and purification technics, the structure, stability and oxidation resistance of the roselle red pigment were studied systematically. The main process parameters and conclusions were as follows:After being smashed and screened, the roselle calyx extracted by alcohol solution to remove part of the polysaccharide, protein and other impurities, and got the crude roselle red pigment. The experiment determined the total anthocyanin content by pH-differential method under 520nm, and optimized the extraction process parameters by the single factor and response surface methodology. The conclusion was following:Among the effect factors, solid to liquid ratio was the main factor, the extraction time and temperature was the secondary factors. The optimum extraction conditions process parameters were the following:solid to liquid ratio is 1:24.8g/mL, extraction time is 1.52h, extraction temperature is 48.74℃, and the corresponding total anthocyanin content is 487.6mg/100g.After comparing the adsorption and desorption rate of XDA-7, AB-8, D101, DA-201, X-5, it showed that XDA-7 was the optimum resin to purify the roselle red pigment. Through the single factor and orthogonal test, the optimum adsorption conditions were that the concentration of the sample was 2mg/mL, the flow rate was 1.75mL/min, pH was 2.76, the adsorption rate was 90.1%. The optimum desorption conditions were that concentration of eluent was 75%, pH of eluent was 3, elution rate 1.5mL/min, the volume of elution was 60mL, and the desorption rate was 94.6%. After the purification, the color value of roselle red pigment was 52.6, which was 7 times as much as which was not purified.The roselle red pigment was identified by UV, IR, and LC-MS. Roselle red pigment was anthocyanin pigment though analyzing the scanning spectrum of UV. It could preliminary be determined the pigment was cornflower-glucoside or delphinium-glucoside though analyzing the spectrum of IR. There were two main components in the pigment through analyzing the result of LC-MS. The molecular weight of Component I (21.55min) was 449.3, which contained a glucoside, it should be cornflower-glucoside pigments. The molecular weight of Component II (38.23min) was 580.8, it should be polymer anthocyanin pigments which bonded through C4-C6, C4-C8.The studies on the stability of the roselle red pigment were showed that:(1) The roselle red pigment remained a relatively stable state under the conditions of pH<3, but when pH>5, the color value changed greatly and the pigment became unstable. (2) The red pigment had a general heat resistance, which remained a relatively stable state when T<60, however, the pigment became unstable when T>80. (3) It also had some light resistance, the pigment would lightly effect under the conditions of dark and room light but not under the sunlight condition, so it should avoid sunlight during processing and storage process. (4) Most of the cations had effect to this red pigment. Mg2+, Zn2+, Ca2+ had little effect to the red pigment, however, Cu2+, Al3+ had a hyperchromic effect, Fe3+ had red shift of absorption peak. So it should avoid contacting with vessels made by Copper, Iron and Aluminum.The studies on the inoxidizability of the roselle red pigment were showed that:(1) As the concentration of the red pigment increasing, the ability of eliminating DPPH, superoxide anion and hydroxyl radical experiment became stronger, and could be achieved to 86.1%,78.5% and 88.1% of Vc when in high concentration although slightly lower than Vc. Therefore, roselle not only could be as a food colorants which could increase human's appetite, but also could be as an antioxidant added into the food to effectively remove the harmful free radicals of body, in one word, it can prevent aging. (2) As the concentration of red pigment increasing, the ability of eliminating became stronger. when the concentration is low, the ability to remove nitrite of the red pigment was 11% of Vc, but when the concentration became 1.25%, the ability could be achieved to 73.9% of Vc.