Study On Extraction, Purification And Properties Of Anthocyanins From Hibiscus Sabdariffa

Roselle is an annual plant of Hibiscus hamabo Sieb et Zucc, its calyx is rich in anthocyanins which is a kind of natural edible pigment. It is a new kind of food additives which not only has the characteristics of high safety and natural colour and lustre, but also has antioxidation and antitumor effects. This article mainly research the extraction, purification and characteristics of roselle anthocyanins, the main research contents and results are as follows:1. The research on extraction technology of roselle anthocyanins(1) Determining the absorption wavelength of roselle anthocyanins is 580nm.Use the content of anthocyanins in first extract as evaluation standard to determine the content of roselle anthocyanins by pH method quickly and effectively.(2) Compare the traditional water bath method and ultrasonic-microwave synergistic extraction method. Using the single factor and orthogonal experiment in traditional water bath method, the results showed that the effects of four factors were: extraction time> extraction temperature> liquid ratio> ethanol volume fraction; the optimum processing conditions are:extraction temperature 60℃, material to liquid ratio 1:20, ethanol volume fraction 40%, extraction time 1.5 h.The anthocyanins content in extract can reach 486.133 mg/100g material on the optimum processing conditions. In the experiment of ultrasonic-microwave synergistic extraction method the effects of three factors were material to liquid ratio> microwave power >extraction time. The optimum processing conditions are microwave power 164 W, material to liquid ratio 1:25, and extraction time 12 min. The anthocyanins content in extract can reach 537.873 mg/100g material. On the optimum processing conditions, the anthocyanins content is 21.517 mg/100 g higher when the ultrasound is open than the ultrasound is close. This suggested that ultrasonic wave had obvious effects on anthocyanins extraction retio of roselle, this is because that the ultrasonic has unique mechanical vibration and cavitation effect, which can rapidly penetrate the cell, make anthocyanins dissolve out in great quantities, and increase the content in extract. The comparison of two methods suggested that ultrasonic-microwave synergistic extraction method can extract more anthocyanins than the traditional water bath method and the anthocyanins content in extract increased from 486.133 mg/100g material to 537.873 mg/100g and the extraction time reduced from 90min to 12 min, which is a high efficient extraction method.2. The research on purification of roselle anthocyanins(1) Through the screening five kinds of macroporous resins:X-5、DA-201、 HPD-100、D101、AB-8, the most suitable resin for roselle anthocyanin purification was HPD-100.(2) Optimize HPD-100 macroporous resin purification conditions, through single factor and orthogonal test, the best adsorption process conditions were liquid concentration 1.5 mg/ml, sample flow rate 2 ml/min, pH 3. The adsorption rate can reach 91.988%. The best desorption process conditions were eluent concentration 70 %, elution velocity 1.75 ml/min, dosage of eluent 60ml.The desorption rate can reach 92.144%. The resin absorption curve showed that the saturated adsorption amount was 3 mg/g.(3) After the purification, the color value of roselle anthocyanins was 54.6, which is 7 times as much as not purified.(4) With cornflower anthocyanin as standard, the high performance liquid chromatography (HPLC) figure of roselle red colors showed that roselle red colors mainly contain five components, after purified by HPLC, the cornflower anthocyanin content increased significantly.3. The research on the properties of roselle anthocyaninsThis chapter mainly research anthocyanins stability and antioxidation.(1) Stability analysisLight has a certain influence to the stability of the roselle anthocyanins. The preserving rate of anthocyanins dropped to 80.7% after 30 days’ storage in natural light outdoor, but the preserving rate was 93.1% when it was in natural light indoor. So during the processing and storage of roselle anthocyanins they should be protected from light; Temperature has a large effect on the stability of anthocyanins. The preserving rate reduced to 63.4% after 4 hours in 100℃ water bath pot, and it was relatively stable in 20～60℃; The change of pH value has a large effec on stability of the roselle anthocyanins. The optimal pH value for the anthocyanins processing and storage is 3.0. The study showed that Fe3+, Cu2+, Al3+ had bigger influence on the stability of roselle anthocyanins.(2) The antioxidation analysisThe results in studying the antioxidation of roselle anthocyanins showed that when the anthocyanins concentration is 0.35 mg/ml, the clearance rate of hydroxyl radical reached 94%, while the ascorbic acid concentration is 0.35 mg/ml, the clearance rate is only 78%.; when the two antioxidants were at the same concentration of 0.65 mg/ml, roselle anthocyanins clearance rate of superoxide anion reached 91%, while ascorbic acid is only 80%; when the anthocyanins concentration is 0.07 mg/ml, its clearance rate of DPPH radical is 97.4%, while ascorbic acid concentration is 0.07 mg/ml, the clearance rate is 94.8%, their removal ability to DPPH radical was similar.