The Study Of Extraction,Purification And Function Of Melanoidins From Cooked Lycium Barbarum

Lycium barbarum is rich in nutrients and active components.The ripening lycium barbarum was made from lycium barbarum as raw material by high temperature and high humidity.The maillard reaction caused the lycium barbarum to change from red to black brown gradually.Melanoidin is a melanin produced by the Maillard reaction,which gives food its special aroma and functional activity.In this paper,ripening Lycium barbarum was used as raw material to study the extraction and purification method of ripening lycium barbarum melanin and analyze its structure and functional characteristics,in order to have a deeper understanding of the characteristics of ripening lycium barbarum given by Maillard reaction.The research results are as follows:1.Uv spectrophotometry was used to determine the content of cooked lycium barbarum melanoidin.The detection wavelength of cooked lycium barbarum melanoidin was 420 nm.Through ultrafiltration separation,the crude extracts of cooked lycium barbarum melanoidin were divided into four fractions,UF₁（>50 k Da）,UF₂（10 k Da-50k Da）,UF₃（3 k Da-10 k Da）and UF₄（<3 k Da）,with the content ratios of 3.52%,12.9%,59.37%and 24.21%.Through the determination of the basic components,the crude extract of melanoflavone in the main position,no flavonoids,phenolic substances only about 0.08%,can be excluded from the influence of these on its antioxidant.At the same concentration,the maximum total reducing power of UF₁ was about 1.12.The hydroxyl radical scavenging rate of UF₄ and DPPH radical scavenging rate of UF₃ reached 96.66%and99.67%,respectively.2.Through static adsorption and desorption experiment,AB-8 resin was selected for purification experiment,and the optimal elution concentration of ethanol solution was 40%.The optimum purification conditions were determined by single factor and orthogonal experiments:loading concentration 4 mg/m L,eluting volume 6 BV,flow rate 1 m L/min.The optimal purification conditions were as follows:the loading concentration was 100mg/ml and the column height was 35 cm.Two components M₁ and M₂ were purified.3.Through infrared spectrum analysis,M₁ and M₂ have no significant difference in structure,and both of them have alcohol hydroxyl,amide group,alkane group,amine group,carboxylic acid,aliphatic ether,ketone group and other functional groups.4.The stability of cooked lycium barbarum melanoidin was studied.The stability of melanoidin was significantly affected by sunlight,and the retention rate decreased to 83%.The temperature above 40℃makes melanoid extremely unstable,so it should avoid the environment with high temperature and sunlight during storage.Under the condition of high concentration of H₂O₂,the retention rate decreases to about 40%.Na₂SO₃ has little effect on the stability of melanoidin,and the retention rate remains above 70%.Among food preservatives,potassium sorbate has no effect on the stability of melanoidin,the retention rate is above 90%,and sodium benzoate has color enhancing effect on melanoidin.5.Five antioxidant indexes,ABTS free radical scavenging rate,DPPH free radical scavenging rate,hydroxyl free radical scavenging rate,total reducing power and metal ion chelating ability,were studied during simulated digestion of melanoidin,cooked lycium barbarum and common lycium barbarum in vitro.ABTS free radical scavenging rate of melanoidin decreased to 16%,and the other indexes retained strong antioxidant activity after digestion.