The Subcritical Water Extraction And Properties Of Purple Sweet Potato Pigment

Purple sweet potato pigment is a water-soluble anthocyanin pigment, the main ingredient iscyanidin acyl glucoside and peony prime acyl glucoside.AS a result of its vivid color, anti-oxidation,anti-mutation,anti-cancer and other physiological activity, purple sweet potato pigment has been widelyconcern as a natural pigment resource which had broad future of development.In this study,purple sweetpotato pigment was extracted with subcritical water extraction and purification,then purified purplesweet potato pigment was studied by the analysis of its antioxidant,stability and optimiza thetechnological conditions of purple sweet potato pigment microcapsules.1)The pigment was extracted from purple sweet potato using subcritical water.Based on theanthocyanin yield,the single factor experiments and orthogonal test were used for the optimization ofpigment extraction conditions.The results showed that the optimal extraction conditions weretemperature110℃,time6min,liquid-material ratio40:1(mL:g),ethanol concentration40%(V/V) andpH2.5.Under this condition the anthocyanin yield was1.897±0.049mg/g.The influence of influencingfactor follows the sequence:temperature＞liquid-material ratio＞ethanol concentration＞time.Thetemperature and liquid-material ratio have significant effect on the yield by the analysis ofANOVA,while other factors have less effect.Compared with ultrasonic extraction and solventextraction,the subcritical water extraction shorten the extraction time and reduce the usage amount oforganic solvents,which is an environmentally friendly and efficient extraction technology.2)The purple sweet potato pigment was purified by AB-8macroporous resin.Afterpurification,anthocyanin content and color value were7.89times compare with non-purified,totalphenolic content was1.29times compare with non-purified.3)The antioxidant activities of anthocayanin from purple sweet potato were evaluated bydetermining the reducing capacity,free radical-scavenging activity on DPPH and ABTS.The values oftests show purple sweet potato pigment has antioxidant activities and the antioxidant activities increasedas the concentration increased.But the antioxidant activities of purple sweet potato pigment lower thanBHT and Vc.4)The stability of purified purple sweet potato pigment were examined by light,pH,oxidizing andreducing agents,common food additive.The results show that:the retention of purple sweet potatopigment were80.59%and94.17%in outdoor natural light and dark chamber for7d respectively.Withthe pH increase, retention of purple sweet potato pigment decreased significantly. Hydrogen peroxideand Na2SO3were obviously harmful to the stability of purple sweet potato pigment.Glucose and sucrose have a certain color enhancement function.Potassium sorbate and sodium benzoate had no effect on thestability of anthocyanins.5)During preparation of purple sweet potato pigment microcapsules using piercing-solidifyingmethod,encapsulation efficiency was used as evaluation index,the single factor experiments andorthogonal test were used for the optimization of technological conditions.The optimal technologicalconditions were sodium alginate concentration3%,cacium chloride concentration2%,core-to-wall ratio1:3,solidify time1h,in which condition the encapsulation efficiency is76.12±1.09%.The sodiumalginate concentration and cacium chloride concentration have significant effect by the analysis ofANOVA,while other factors have less effect.Subsequent tests prove that the stability of the purple sweetpotato pigment microcapsules had improved compared with these did not microcapsules in the samelight condition.