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Physicochemical properties of aggregates of globin hydrolysates

Liu, X.Q., Yonekura, M., Tsutsumi, M., Sano, Y.
Journal of agricultural and food chemistry 1996 v.44 no.10 pp. 2957-2961
animals, blood, citric acid, food industry, food science, functional properties, gel chromatography, gels, hydrolysates, hydrolysis, ingredients, light scattering, meat products, models, molecular weight, pH, polypeptides, solubility, thyroglobulin, transmission electron microscopes
Globin is an edible protein that is obtained in large quantity from animal blood. It can be used as an ingredient in a variety of meat products. However, globin showed a rather low solubility at neutral pH and little advantage compared with other proteins used in the food industry. The effective use of latent materials is an important research area in food science. This study succeeds in improving globin's functional properties and explaining the mechanism of gel formation. The hydrolysis of globin was performed with 0.8 M citric acid. The globin hydrolysates showed eight bands by tricine-SDS-PAGE having molecular masses that ranged from 5000 to 15 000 Da. The results of gel filtration chromatography indicated that the large aggregates were formed easily in the case of the globin hydrolysates. Physicochemical properties of aggregates of globin hydrolysates were studied by light scattering measurement and transmission electron microscope. It is clear that the aggregates were composed of two kinds of polypeptides, one of which, the beta-chain, originated from the native globin and another, beta-1, originated from the beta-chain by cleavage between 99 (Asp) and 100 (Pro) of the beta-chain through noncovalent bonding. By comparison with the position of standard protein (thyroglobulin, MW 669 000 Da), the molecular mass of the aggregate was estimated as above 700 000 Da. The aggregates of globin hydrolysate in solution approximated the thin rod-shaped model and had lengths of 130-140 nm by light scattering measurement. Electron micrography also showed the aggregates to consist of the thin rod aggregates. The molecular mass of the aggregates was determined to be 870 000 Da by light scattering measurement, indicating that the aggregate consists of 33-34 units because each unit was in the ratio of 1:1 complex of beta-chain and beta-1 with molecular masses of 16 000 and 10 9000 Da, respectively.