Purple Corn Cob Pigment Research On Extraction And Purification And Oxidation Resistance

Extraction&purification of purple corn cob pigment, and effect of several organicacids&metallic ions on the pigment’s stability, are dealt with in the paper. The organicacids to have hyperchromic effect on the purple corn cob and metallic ions to weakenthe color, are optimally sieved to function as co-colored action. Optimal concentrationsof organic acids, optimal concentration of metallic acids, optimal temperature of thepigment, optimal extraction temperatures, are specified in uniform design experimentby maximum target function. Furthermore, the optimal results are verified.Themechanism to aid the color is primarily discussed in UV, IR, HPLC by choice of anorganic acid and a metalicion. Antioxidation and stability in food are also involved inthe paper to supply theoretical application criteria for the purple corn cob. The resultsare as follows:（one）Optimal processing operations as to60%molar fraction of ethanol,80mesh,60:1ratio of liquid to solid,3h extraction time, are achieved in solvent extraction of thepurple corn cob. The6.88%yield of the pigment is available,the color value14.Cyanidin-3--glucoside content0.0224mg/g.（two） Based on adsorption capacity, adsorption rate, desorption rate, adsorptionequilibrium rate as testing index, the adsorption and desorption performances of5macroporous resins on the purple corn cob are compared. Moreover, the characteristicmechanism are examined in the paper, The results show that the AB-8resin is areasonably perfect resin and its adsorption to the cob follows Freundlishisotherm.Optimal dynamic desorption parameters are as follow: the sampleconcentration of3.8681g/mL, flow rate of1.5mL/min, elution flow rate of1mL/min,ethanol concentration of30%. Additionally, effective adsorption chromatographyadsorption capacity can reach77.63%volume. Under the separation condition, the colorequivalent is48,3.5times as much as that before separation, which is over currentNational Standard, namely color equivalent of8.（three） Effect of the organic acid on stability of anthocyanion of purple corn cobpigment.The percent storage in the pigment solution at pH=3is larger than at pH=5,whereas percent storage of high concentrations over that of low concentration is notassociated with organic acids.The percent storage of the pigment solution at pH=5derived from glycine,as well as that at pH=3derived from tannin acids,is higher than that of reference solution.Baseon activation,high concentration pigment solution has a better thermal stability afteraddition of coumarin,tannic acid,malonic acid,cinnic acid,glycine,i.e.the organic acidsare able to increase the thermal stability of the pigment solution.Howere,low concentionpigment solution has a better thermal stability after addition of coumarin,tannicacid,DL-mlic acid,cinnic glycine.In terms of half-life,the thermal stability of thedecreases at elevated temperature in the presence or absence of the organic acids.Thesecondary color is not significant at90℃in the presence of organic acids.The said metallic ions,except Fe²⁺,have a distinct effect on the stability ofanthocyanins,but no distinct effect on others.By means of uniform design the optimalresults are as follow:the3.76g/mL of pigment,1.25mmol/L of glycine256mmol/L ofFe²⁺,75℃temperature,pH=5of the solution under which secondary color is developedand inhibition of Fe²⁺on the destruction of pigment’s stability is also developed.Furthermore,H2O2and Vc reduce the system’s stability,whereas Nacl has ahyperchromic effect on the system.UV spectrum possibly shows that the hydroxyl ofanthocyanins are substituted by metoxy namely,the acyl group in the anthocyanin isacrylated to ferulic acid or ecffeic acid;IR spectrum indicates that there are considerablequantities of esteric groups after esterification of the anthocyanins;LC spectrum revealsthat the relative content of the anthocyanins varies after modification of theanthcyanin.Its detailed structure will necessarily be established by LC/MS and NMR.（four）The removal yield derived from the pigment to remove superoxide anionradical is greater than that derived from Vc to do.The efficiency for both the pignmentand Vc to remove hydroxyl radical increases with increasing the their massconcentrations and reaction time.The efficiency for the pigment to remove at lowconcentration is slightly advantageous over that for Vc to do.The efficiency for pigmentto remove at high concentrations is comparable to that for Vc to do.The removed ofDPPH reaches steady state in30min both in the presence of the pigment and in theabsence of the pigments.The removal of DPPH in acidic medium is stronger than thatin alkaline medium.The removal capacity of the pigment to remove DPPH is largerthan that of Vc when the concentration is less than0.1mg/mL,and EC₅₀values for theboth are0.4753mg/mL and0.3359mg/mL respectively.Low EC₅₀is comparable tostrong removal capacity at which Vc capacity is slightly greaterer than thepigment’s.The pigment in carbonated beverage is more stable than that in yogurt or thatin XiaoBuDing Ice-cream.The degradation rate of the pigment in beverage follows the zeroth-order,whereas one in yogurt follows the first-order at high concentration,zerothat low concentration.