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The full compliance date for mandatory folic acid fortification of enriched cereal-grain products in the United States was 1 January, 1998. There is currently a great interest in determining the effectiveness of this measure, which was instituted to increase the folate intakes of women of child-bearing age to reduce their risk of having a pregnancy affected by a neural tube birth defect. We surveyed 83 enriched cereal-grain products that are required to be fortified with folic acid under the new regulations and an additional 79 foods that contain enriched cereal-grain ingredients or that are currently fortified with folic acid. Products were collected and analyzed between February 1998 and April 1999. Total folate was determined by microbiological assay using a tri-enzyme digestion. We compared analyzed values for total folate with amounts required by Federal regulations and/or with label declarations of folate content. For many enriched cereal-grain products, there were significant differences between amounts of folate found on analysis and amounts required by Federal regulations. In part because of this, label declarations of folate content were also in error. The high values found in some enriched cereal-grain products may represent manufacturers' averages as well as the presence of higher-than-expected levels of endogenous folates. These results indicate that reliable food composition databases cannot be developed without extensive new data on the actual concentrations of folate in recently fortified enriched cereal-grain products as well as in products containing enriched cereal-grain ingredients. Reliance on older data bases or on compositional information that has a weak analytical underpinning will lead to unsound estimates of folate intake, and hence, of the potential impact of the new fortification program.

January 1, 1998 was the effective date for PDA regulations that mandated the fortification in the USA of a wide range of enriched cereal-grain products with folic acid at levels specified in federal regulations. Because data on prefortification levels of folate in such products are limited, we measured folate in 56 enriched foods, including enriched breads and rolls, flours, corn grits and meals, rices, and macaroni and noodle products. Folate was measured by a modification of the Association of Official Analytical Chemists' microbiological method 992.05 using Lactobacillus casei . Foods were composited, suspended in 0. 1 m phosphate buffer containing 1% ascorbic acid (pH 7.8), autoclaved and cooled. Chicken pancreas conjugase was added and the suspensions were incubated for 16h at 37 °C. Values for folate in enriched products were (μg/lOOg): bread and rolls, 24–40; flours, 19–24; corn grits and meals, 22–32; macaroni and noodle products, 27–42; rice, 19–32. Because the single-enzyme method is usually insufficient to liberate food-bound folates, suspensions of foods were also incubated with α-amylase and conjugase followed by treatment with protease to determine the effects of the tri-enzyme digestion on release of folates. For many foods, total folate was 20–30% higher after the tri-enzyme digestion than after incubation with conjugase alone. The modifications of AOAC method 992.05 described here provide a microbiological assay method for the determination of folates in cereal-grain products that may be appropriate for collaborative testing.