Extraction, purification and characterization of globulin from common buckwheat (Fagopyrum esculentum Moench) seeds

Abstract

Salt-soluble globulin was extracted from common buckwheat (Fagopyrum esculentum Moench) seeds. The protein content of buckwheat globulin (BWG) was over 90%. Anion-exchange chromatography (with stepwise salt gradient elution) was used to obtain two fractions of BWG, corresponding to the basic and acidic polypeptides, respectively, at a ratio of approximately 1:2. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the acidic and basic polypeptides were linked by disulfide bonds. The basic polypeptide has an estimated molecular weight of 23–25 kDa, an isoelectric point in slightly alkaline region (pH 8–9), and showed a high degree of homology with other legumin-like proteins. Disulfide and sulfhydryl contents in BWG were estimated as 36.4 and 3.20 μM/g of protein, respectively. BWG exhibited beneficial functional properties such as high solubility, emulsifying activity and emulsion stability, while the foaming properties were relatively poor. BWG had lower water holding capacity and comparable fat binding capacity when compared to a commercial soy protein product.