Comparison of Vitamin B 1 Content of Raw and Evaporated Milk by the 10-Day Bio-Assay Method

Abstract

The amount of vitamin B₁ destroyed in the process of dehydration and sterilization involved in the production of evaported milk has been variously reported. Hartwell, 1 by means of lactation tests, found approximately a 50% destruction in some of the milks tested, 33 cc. of fresh cow's milk being almost enough and 50 cc. quite sufficient to meet the needs of the lactating rat and 6 young, when used in conjunction with the basal ration; whereas 75 cc. of evaporated milk was found to be too little. Daniels and Brooks, 2 and Daniels, Giddings, and Jordan, 3 using a similar technique with a slightly modified diet, obtained similar results. Feeding tests with pigeons (Donath, 4 and Daniels and Brooks²) also indicated that the evaporated milks tested contained approximately 50% less vitamin B₁ than the raw milk used in comparative tests.

Samuels and Koch, 5 on the other hand, by 2 different methods: a modification of the Hartwell 1 lactation test, and a direct feeding procedure, found only about one-sixth less vitamin B₁ in the evaporated milks, while Dutcher, Francis and Combs' believe the difference in the potency of raw and evaporated milk to be so slight as to be negligible. These authors state: “Vitamin B is not readily destroyed by the evaporation process used, and only under unusual conditions would we expect the deficiency of commercial evaporated milk to be due to the process of manufacture.”

The lack of unanimity in these reports has led to a study of the vitamin B₁ content of raw Guernsey milk (4.5% fat) and commercial evaporated milk (diluted 1:1) by a modification of the 10-day bio-assay method of Schlutz and Knott. 7 Young rats at weaning were fed a purified vitamin B₁-free ration consisting of: 20 gm. triple precipitated alcohol-extracted casein, 54.5 gm. cane sugar, 19 gm. Crisco, and 3.5 gm. Wesson's salt mixture. 8 In addition, each animal received 2 drops of cod liver oil.