Extraction And Purification,physical And Chemical Properties,and In Vitro Digestion Of Maca Protein

Recently,more and more studies have shown that Maca has a variety of physiological activities which made Maca more and more popular in the market.But most of the studies just tested the properties of whole Maca and most of the potential efficient functional substances have not been studied yet.Maca protein is the main component of Maca,in order to promote the development of Maca and improve its comprehensive utilization,Maca protein has been systematically studied in this research.Maca roots was used as raw material in this study.Single factor and response surface experiment design were applied for the optimization of Maca protein extraction process.The results showed that the optimal Maca protein extraction conditions were: Tris concentration as 0.07 mol/L,extraction temperature as 60 ?,pH 10,extraction time as 30 min,mass to volume ratio value as 1?45(g/m L),and under these conditions,Maca protein extraction ratio reached to 90.67%.In addition,the isoelectric point of the protein was measured.The results showed that the optimum pH was 3.75 with the precipitation rate as 74.04%.The fundamental physical and chemical properties and physicochemical function of Maca protein were studied.The results showed that Maca protein had all kinds of the essential amino acids.It was rich in sulfur-containing amino acids and hydrophobic amino acids with the first limiting amino acid as isoleucine.The solubility of Maca protein was 90%(pH = 9).Oil and water absorption of Maca protein were 5.57 g/g and 9.73 g/g,respectively.Foaming and emulsification capacity were 100% and 14.30%,respectively.The free sulfydryl content was as high as 23.92 ?mol/g and the denaturation temperature was 87.36 ?.Built the purification method of Maca protein.The purification conditions of DEAE Sephrose FF chromatograph were as follows: flow rate was 1m L/min,eluent was 0.02 mol/L Tris with pH 8.0,loading quantity of Maca protein was 20 m L with a concentration of 5 mg/m L.Sephadex G-100 chromatograph conditions:Flow rate was 0.18 m L/min,eluent was 0.02 mol/L Tris with pH 8.0,loading quantity of DEAE Sephrose FF chromatograph purified Maca protein was 2 m L with a concentration of 10 mg/m L.The preliminary structure of purified Maca protein was identified.The purification of purified Maca protein were reach to the grade of high performance liquid chromatography and electrophoretic pure.And it is tentatively speculated that Maca protin was a multimer of five subunits with a molecular weight of 22.5 ku.The secondary structure of Maca protein was mainly consisted of ?-helix with a percentage about 52.6%.Besides ?-sheet content was about 8.6%,?-angle was about 15.6%,and the irregular curl was about 22.4%.The effects of boiling process on the digestion of Maca protein were studied.The results showed that after in vitro digestion,the protein was hydrolyzed into the product with a molecular weight between 612-1450 Da which is accounted for 99.82% and 62.18% of the corresponding product,respectively.Among them,there are still 19.12% of product of the untreated protein remained a molecular weight between 1450-5734 Da.The free nitrogen release rate of in vitro digestion of Maca protein were 13.69% and 26.76% respectively,after boiling cooked and untreated preparetion.ABTS scavenging rate were 79.74%(treated)and 72.06%(untreated)respectively,Fe3+ reducing capacity were increased to 0.476(treated)and 0.336(untreated)with a significant difference.