Comparison of Microbiological and Radiometric Assays for Determining Total Folacin in Spinach

Several commercially available forms of spinach were analyzed for total folacin content by the microbiological assay using Lactobacillus casei and a radiometric assay. Types of products included frozen uncooked, fresh raw, microwave and conventionally cooked fresh and creamed strained spinach. Folacin content ranged from 0.62 mcg/g for strained spinach to 2.50 mcg/g for uncooked frozen spinach, when assayed microbiologically. With the radiometric assay, folacin values were significantly higher (P<0.05) than with the L. casei assay. The microbiological assay appears more suitable for determination of total folates in complex food matrices than the radioassay.