Collaborative Study of Microbiological Assay for Folic Acid in Food

Abstract

Abstract The extraction and microbiological determination of folic acid in foods was studied collaboratively. Four samples and four extraction procedures were used. Extracts were assayed for folic acid activity with L. casei and S. faecalis, and chick assays were also made on the samples. The four extraction procedures were: (A) Incubating 4 hours with chick pancreas at 37 °C after autoclaving 15 min. at 15 lb in 0.2M pH 7.2 phosphate buffer and cooling; (B) autoclaving 30 min. at 15 lb in potassium ascorbate (pH 6.0, 6 mg/ml); (C) incubating 4 hours with chick pancreas enzyme after autoclaving 15 min. at 15 lb in 0.2M pH 8 phosphate buffer, cooling, and adding potassium ascorbate (20 mg/ml, pH 6) in volume equal to the phosphate buffer; and (D) autolyzing in incubator 4 hours at 37 °C in mixture of equal volumes of potassium ascorbate (20 mg/ml, pH 6) and 0.2M phosphate buffer, pH 8.0. The highest values were obtained with L. casei in extracts containing potassium ascorbate. A rough estimation of the types of folic acid derivative in each extract could be made by comparing values obtained in the various extracts with each organism. Collaborators’ results by chick assay agreed fairly well with those by microbiological assay, but further work is needed to standardize the extractions and both types of assays.