Determination of Cobalamin and Related Compounds in Foods

Cobalamin, also known as the red-colored vitamin B12, is found in animal-based foods such as meat, milk, and fish. Various cobalamin compounds are extracted from foods and converted into cyanocobalamin, which is most stable, to be analyzed by various methods. Traditionally, the cobalamin content of foods is determined by microbiological assay with Lactobacillus delbrueckii subsp. lactis American Type Culture Collection 7830. However, this lactic acid bacterium can substitute deoxyribosides or deoxynucleotides (known as an alkali-resistant factor) for cobalamin. Therefore, cobalamin contents determined by this microbiological assay are often incorrect in some foods. The difficulty of evaluating whether certain foods contain cobalamin or inactive corrinoids (or both) may be easily resolved by the use of bioautography with a cobalamin-dependent Escherichia coli after separation of the sample by silica gel TLC. LC/electrospray ionization-tandem mass spectrometry is also used to analyze corrinoid compounds, and various inactive corrinoid compounds have been identified in foods.