Study On The Extraction, Separation, Stability, And Antioxidant Activity Of Pigment From Seed Coats Of Wild Soybean

ObjectiveTo study on the technology of extraction,separation and purification of pigment from seed coats of wild soybean,and to determine its stability,antioxidant activity and content,for further utilization.MethodsThe pigment was extracted with acidic ethanol from seed coats of wild soybean by ultrasonic wave.The optimum extraction conditions were determined by single factor and orthogonal tests.The purification of pigment by macroporous resin were studied.The stability was studied by spectrophotometry,under different pH,illumination,temperature, metal ions,reductant,oxygenant,potassium sorbate and nutritional ingredient.The scavenging activity on free radical and total antioxidant capacity of pigment from seed coats of wild soybean were determined by DPPH and FRAP methods,respectively.The content of anthocyanins and proanthocyanins in the seed coats of wild soybean were determined,respectively.ResultsThe optimum extraction conditions of pigment from seed coats of wild soybean were as follows:pH 2.3,ethanol concentration 60%,ratio of solid to liquid 1:20,temperature 60℃,extraction time 90 minutes.The best type of macroporous resin was AB-8.The conditions of separation and purification were:speed of sample injection 5 ml/min, concentration of eluting reagent 70%ethanol,washing speed 3 ml/min.The pigment was relatively stable under reductant and the acid condition;It could be kept for a long time under different light or temperature conditions;It was unstable under Fe³⁺ and oxygenant; Potassium sorbate,a food preservative,had no influence on its stability at normal dose;It was stable under glucose,lactose,sucrose,citric acid and L-lysine while it was unstable under vitamin C and L-tyrosine.The antioxidant activity and scavenging activity on free radical of extraction of pigment from wild soybean(three ecological types) were stronger than the three cultivated black soybeans.The scavenging activity on free radical was equivalent to 30.48%,40.80%,44.81%of vitamin C.The total antioxidant capacity was equivalent to 27.65%,29.45%,30.12%of vitamin C.The ranges of anthocyanin and proanthocyanidin contents in wild soybean were 0.09%～0.12%and 0.28%～0.38%, equivalent to 1.8～4.0 and 5.6～9.5 times of cultivated black soybeans,respectively.ConclusionThe pigment of seed coats in wild soybean could be used in food and medicinal industry for its easy extraction,stability and antioxidant activity.