258. The Vitamin B1and Riboflavin of Milk

Abstract

Part I1. A method for the estimation of vitamin B1in milk by a modified Jansen test involving takaphosphatase treatment is described in detail.Part II2. It is shown by ultra-filtration experiments, by treatment with pepsin and takaphosphatase, with trichloroacetic acid and with fuller's earth that vitamin Bx is present in milk unesterified and phosphorylated and that both forms may be freely diffusible or combined with protein either loosely or by firmer bonds.Part III3. The effect of the stage of lactation on the amounts and partition of vitamin B1in milk has been studied. Samples of colostrum and early milk were found to contain large amounts of cocarboxylase (up to 80 % of the total). Hardly any cocarboxylase was present in mid or late lactation milks. The total vitamin B1content was 60–100μg./100 ml. for colostrum, up to 60μg./100 ml. for early milk and 30–40μg./100 ml. for mid and late lactation.4. A marked negative correlation exists between the cocarboxylase content of cow's and goat's milk and their alkaline phosphomonoesterase titre. As this enzyme cannot dephosphorylate cocarboxylase it is probably accompanied in milk by other enzymes more suited to this process.5. The suggestion is put forward that the vitamin B1of milk is mostly derived not directly from the blood but from the secretory cells of the mammary gland.