Study On Preparation, Structure Identification And Stability Of Red Pigment From Jujube Rind

In this paper, jujube rind of Shanxi Datan Jujube was chose as the raw material, the extraction, purification and stability of red pigment from jujube rind were studied, the major components and sturcture of the pigment were indentified, and the coloration quality of jujube rind red pigment and monascus red were comparatively analysed. The research provided a reference for the development and application of red pigment from jujube rind. The main results are as follows:(1) The extraction of red pigment from jujube rind was studied by using the conventional solvent extraction and microwave assisted extraction. The optimum conditions for solvent extraction were as follows: the concentration of NaOH was 0.37mol/L, the extraction time was 2.5h, the ratio of material to solvent was 1:27 g/mL, the temperature was 85℃, extract 2 times and the extraction yield reached 94.85%; The optimum conditions for microwave assisted extraction were as follows: the microwave power was 240W, the concentration of NaOH was 0.50mol/L mol/L, the extraction time was 180s, the ratio of material to solvent was 1:20 g/mL, extract 2 times and the extraction yield reached 94.85%; There were no obvious difference in the extraction yield of two methods, but the extraction time of microwave assisted extraction was only 6 min, which is much smaller than solvent extraction.(2) The results of purification were as follows: the purification ability of macroporous resin LX-60 was much better than others. The optimum conditions showed that the pigment concentration 1.50(absorbence), absorption speed 1.0mL/min at room temperature, the eluant (alcohol) concentration 50%, desorption speed 1.0mL/min at room temperature. After the purification, the red pigment yield was 2.61%, the colourity was 15.49, which was 4.78 times before purification.(3) The stability of red pigment has been studied. The results showed that, the pigment was stable to weak acid, neutral and alkaline solution, the temperature and edulcorator. The sunlight and food acids such as citric acid and ascorbic acid had significant effects of the pigment. The pigment had definite antioxidant and reduction prosperities, it's stable to Na2SO3 and H2O2 of low concentration. The pigment was stable to sodium benzoate and Nisin of low concentration, both of which enhanced its stability. The pigment was very sensitive to the metal irons Fe³⁺,Fe²⁺,Cu²⁺,Al³⁺ and stable to K+,Mg²⁺,Ca²⁺,Zn²⁺ which can enhance its stability.(4) By the methods of infrared spectrum and LC/MS, the framework of aromatic ring, C=O and -OH of alcohol or phenol were inclued in the structure. The formula weight of three componets were 342.2,363.3 and 328.1.(5) The comprative analysis of stability between Jujube rind red pigment and monascus red were studied. The conclusions were as follows: the Jujube rind red pigment had much better stability to sunlight and heat than monascus red, but monascus red had much better coloration quality than Jujube rind red pigment.