Milk of Northern Fur Seal: Composition, Especially Carbohydrate and Protein

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Abstract
The milk of northern fur seals was analyzed with special interest in carbohydrate and protein. High solids (61%) and fat (45.6%) were characteristics of its gross composition. Fatty-acid distribution showed that > 22% of the fatty acids had C chains longer than 20 and that .apprx. 70% contained one or more double bonds. Analysis of free sugars showed no lactose but 123 mg/100 ml of myo-inositol. In carbohydrates bound to casein, 0.99% of sialic acid and 0.2% of glucosamine were determined. The amino acid composition of casein showed higher Trp, Lys, Ser, and Gly than bovine casein, and lower Arg, Pro, and Leu. In whey, Arg, Thr, and Val were higher, whereas Lys, Asp, Ile, and Leu were lower than in bovine whey. Amino acid patterns in casein and whey were similar to those of cat milk. The appearance of casein micelles was similar to bovine casein micelles. The mean diameter, however, was larger (.apprx. 330 nm). Electrophoretic pattern of casein showed 5 major bands in addition to minor components. One of the minor components was a glycoprotein, proably .kappa.-casein-like protein. The major whey protein had a mobility similar to that of bovine .beta.-lactoglobulin. No .alpha.-lactalbumin-like protein was observed. [This study has implications for infant formula for zoo reared seals.].

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