Study On Extraction, Purification And Stability Of Anthocyanins From Purple Sweet Potato

Base on the material of purple sweet potato “Jihei” in this paper, the conditions ofextracting anthocyanins were optimized through Response surface method(RSM). Then pureanthocyanins was gained from the crude extract by a macroporous adsorption resin. On the otherhand, the factors such as temperature, pH, metal ions, the copigments, oxidant and reducingagent which effect on the stability of the purple potato anthocyanins were studied. Finally,discussed the antioxidant activity of purple potato anthocyanins. All of these could offer thereference for the industrial production and application. The main results were summarized asfollows:On the basis of single factor experiments, response surface method(RSM) experimentaldesign was employed to establish the mathematical models of purple sweet potato anthocyaninsextraction. The optimal conditions were as follows: alcohol concentration60%, extraction time127min, liquid to ratio of solid18. The actual extraction yield was2.680mg/g, which wasclosed to the theoretic value0.3%. So the model was feasible.The results of static adsorption-desorption and dynamic adsorption-desorption experimentsshowed that XDA-7resin was a preferable macroporous resin among the ten resins forseparation and purification of purple sweet potato anthocyanins. The optimum adsorption anddesorption conditions were that: the concentration, pH and flow velocity of the sample were450mg/L,4.0and1BV/h, respectively. The eluent was60%ethanol aqueous and its flow velocitywas2BV/h.The degradation of purple sweet potato anthocyanins was followed fist-order reactionkinetics. The degradation prediction model was established through mensurating the changes ofresidual rate of anthocyanins at different pH values and heating temperatures. Ca2+in theconcentration of1800mg/L had obviously protective effect on the purple sweet potatoanthocyanins at pH7.0in90℃; the other metal ions had no significant effect. At pH3.0and7.0in90℃, VC, the tea polyphenols, Na2SO3and NaNO2also had no significant effect. H2O2hadobviously destructive effect. The higher the concentration, the stronger the destruction.The purple sweet potato anthocyanins exhibited a scavenging activity against DPPHradicals, O2-·radicals and·OH radicals, the IC50value respectively were1.245mg/L,332.291mg/L and70.830mg/L. The total antioxidant capacity was101.38U/mg, which suggested the purple sweet potato anthocyanins had very excellent antioxidant activity.