Dairy Chemistry And Biochemistry

(^288) DAIRY CHEMISTRY AND BIOCHEMISTRY
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Vitamin B,,
tion in milk is not influenced greatly by feed, breed or season. Higher
concentrations are found in colostrum than in mature milk.
The BIZ-binding proteins of human milk have been studied in detail. The
principal binding protein (R-type B , ,-binding protein) has a molecular mass
of c. 63 kDa and contains about 35% carbohydrate. Most or all of the B,,
in human milk is bound to this protein. A second protein, transcobalamin
11, is present at low concentrations.
Raw ovine and pasteurized caprine milks contain 0.6 and 0.1 pg B,, per
100 g, respectively. Human colostrum contains 0.1 pg per 1OOg but the
mature milk contains only traces of B12, Concentrations of B,, in dairy
products (Appendix 6A) include about 0.3 pg per 100 g for cream and 1 pg
per 100 g for many cheese varieties. Yogurt contains roughly 0.2 pg per 100 g
of this nutrient.
Vitamin B,, is stable to pasteurization and storage of pasteurized milks
(c 10% loss). UHT heat treatment, and in particular storage of UHT milk,
causes greater losses. Storage temperature has a major influence on the