In this study the folate contents in several rye varieties and their fractions were determined. Total folate content was analysed microbiologically using chloramphenicol-resistant Lactobacillus rhamnosus as the growth organism. The amount of folate in rye grains was high, 630–780 µg kg−1, and variation between varieties was 8% (% CV). Affinity chromatography purification (with folate-binding protein from bovine milk) followed by high-performance liquid chromatography (HPLC) analysis proved to be an effective method for determining folate vitamers. 5-Formyltetrahydrofolate showed a lower affinity to the folate-binding protein than other vitamers; in order to obtain recoveries over 90%, the total folate load should not exceed 25% of the column capacity. Owing to intefering compounds, fluorescence detection was not always as specific as UV detection and thus not adequate for peak identification and quantitation alone. Formylated folates and 5-methyltetrahydrofolate were the most abundant vitamers in rye, with tetrahydrofolate and folic acid representing only a minor proportion. However, different milling fractions had different folate vitamer distribution patterns. Both microbiological and HPLC methods were useful and reliable in determining folates in rye.
© 2001 Society of Chemical Industry