PROTEINS FROM CRAMBE ABYSSINICA OILSEED - II - BIOCHEMICAL AND FUNCTIONAL-PROPERTIES

Little information is available concerning the properties of proteins that constitute a major component of the seed of Crambe abyssinica. Th erefore, a method was developed to isolate these proteins. This proced ure resulted in two fractions, an isoelectric precipitate (Fraction 1) and a retentate after ultrafiltration (Fraction 2). Biochemical and f unctional properties of both fractions were studied. Gel permeation ch romatography revealed that high-molecular-weight proteins (>669,000 Da ) are present only in Fraction 1, whereas Fraction 2 consists of prote ins with lower molecular weights (<200,000 Da). Sodium dodecyl sulfate -polyacrylamide gel electrophoresis, in the presence of mercaptoethano l, showed that both fractions consist of proteins that range mainly fr om 40,000 to less than 14,400 Da. Fraction 1 was highly soluble only a t acid and alkaline pH values, while the solubility of Fraction 2 rema ined 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 i ncreased significantly that of Fraction 1 in the isoelectric range. Fo aming properties of Fraction 1 were better than those of chicken egg w hite only at pH 9, whereas those of Fraction 2 were superior at almost every pH value studied. Addition of NaCl improved significantly the f oaming properties of Fraction 1 at all pH values tested but did not ha ve a profound effect on the foaming properties of Fraction 2. Both fra ctions had good emulsifying properties only at alkaline pH values.