Vitamin B12 Content of Organ Meats

Abstract

The microbiological method of assay for vitamin B₁₂ using L. leichmannii 327 as the test organism has been further investigated. Additions of KCN, NaNO₂ or thioglycollic acid to the sample or assay medium did not improve the assay method over that of short term autoclaving ad subsequent assay with the use of an amino acid medium containing thioglycollic acid. The vitamin B₁₂ potency of composite samples of liver, kidney, pancreas, spleen, heart and lung, from beef, pork, and lamb, and of brain and liver from old cows and sows was determined. Liver and kidney were found to be the richest source of the vitamin, and the meats of beef organs were higher in vitamin B₁₂ potency than those of pork. Pancreas was found to contain considerable vitamin B₁₂ activity after alkali treatment when assayed with L. leichmannii, but not when assayed with E. gracilis. Limitations in the use of alkali lability as an index of the true vitamin B₁₂ potency of samples are discussed.