Comparative Review of the Thiochrome, Microbial and Protozoan Analyses of B-Vitamins

A comparative review of the specificities of various B-vitamin analysis methods is presented. Methods of vitamin analysis employing protozoa, viz. Tetrahymena and Ochromonas , are compared to the commonly used methods of vitamin assay, including officially accepted methods. Since 1968 the protozoan techniques have routinely been used to evaluate clinical vitamin status. This is due to their more mammalian-like response to the various forms of the vitamins that occur in natural materials. Protozoa have more developed ingestive and digestive systems than bacteria and yeast, which allow them to respond to conjugated forms of the vitamins (e.g. thiamin pyrophosphate and folic acid polyglutamates). Also, fewer problems are encountered with non-specific stimulation (e.g. fatty acid stimulation of the Lactobacillus casei assay for riboflavin or the sparing of the vitamin B₁₂ requirement of Lactobacillus leichmannii by deoxyribosides). Application of the protozoan methods to analysis of foods indicate significantly lower levels of biotin and vitamin B₁₂ than official methods, while significantly higher levels of riboflavin, vitamin B₆, niacin and pantothenic acid are found in low-acid foods. This review also summarizes extraction methods for the B-vitamins from food samples and indicates the importance of enzymatic hydrolysis in extract preparation.