Proteins from Crambe abyssinica oilseed. II. Biochemical and functional properties

Abstract

AbstractLittle information is available concerning the properties of proteins that constitute a major component of the seed of Crambe abyssinica. Therefore, a method was developed to isolate these proteins. This procedure resulted in two fractions, an isoelectric precipitate (Fraction 1) and a retentate after ultrafiltration (Fraction 2). Biochemical and functional properties of both fractions were studied. Gel permeation chromatography revealed that high‐molecular‐weight proteins (>669,000 Da) are present only in Fraction 1, whereas Fraction 2 consists of proteins with lower molecular weights (<200,000 Da). Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, in the presence of mercaptoethanol, showed that both fractions consist of proteins that range mainly from 40,000 to less than 14,400 Da. Fraction 1 was highly soluble only at acid and alkaline pH values, while the solubility of Fraction 2 remained high (>80%) over the whole pH range tested. Addition of NaCl did not have any profound effect on the solubility of Fraction 2, but it increased significantly that of Fraction 1 in the isoelectric range. Foaming properties of Fraction 1 were better than those of chicken egg white only at pH 9, whereas those of Fraction 2 were superior at almost every pH value studied. Addition of NaCl improved significantly the foaming properties of Fraction 1 at all pH values tested but did not have a profound effect on the foaming properties of Fraction 2. Both fractions had good emulsifying properties only at alkaline pH values.