Studies on the response of Lactobacillus casei to folate vitamin in foods.

1. Folate was measured microbiologically with Lactobacillus casei in extracts from a range of different foods at two incubation pH values, 6.1 and 6.8. 2. The values for folate content obtained at pH 6.2 were, in several instances, considerably higher than at pH 6.8. The 'positive drift' seen in the values for dilutions incubated at pH 6.8 were absent from results at pH 6.2. 3. A comparison was made of the ability of the two main sources (hog-kidney and chicken pancreas) of deconjugase enzyme to produce measurable folate and the hog-kidney enzyme was shown to produce consistently higher values. 4. The results presented here will have significance for studies of folate intake using calculations from food composition tables, in the light of the apparent discrepancy between calculated folate intake and the recommended daily allowances for the UK.