FOLATE LEVELS IN FOOD—A COMPARISON OF MICROBIOLOGICAL ASSAY AND RADIOASSAY METHODS FOR MEASURING FOLATE

Abstract

ABSTRACT Concentrations of N5‐methyltetrahydrofolic acid (N 5 MTHFA) were determined by the radioassay and the L. casei microbiological assay methods. The correlation coefficient for samples analyzed by both methods was 0.93. The radioassay method was found to be faster, simpler and more accurate than the microbiological method. The milk folate binder and L. casei were found to react differently to pteroylglutamic acid compared to N 5 ‐MTHFA acid. The two methods are suitable only for measuring the form of folate used to construct the standard curve for the assay. Therefore, neither method can be used to accurately quantitate folate levels in foods.