Determination of folate for food composition data : development and improvement of analytical methods

Abstract: Folate is B vitamin that is required for maintaining normal blood status. Recommendations on daily intake are based on information on blood folate status in relation to folate intake and bioavailability. Folate intake from a diet is evaluated by folate content in the food consumed. In Sweden folate intake is evaluated on a regular basis in food consumption surveys by the National Food Agency (NFA). Folate content in foods is determined at NFA for the Swedish food composition database with a microbiological assay (MA), an international standardized method. In 2008 sampling of eggs was made for reassessment of folate content and for this study for investigation on effects on folate content from production form and processing. In folate determination the extraction procedure is a critical step that needs to be validated for the folate forms present in the food analysed. Due to the labile nature of some folate forms, the vitamin might be destroyed during the extraction process with underestimation of folate content as a consequence. With MA total folate content is determined and another approach has to be used in order to matrix validate the extraction in respect of stability and glutamate forms of the present folates. In eggs the chemically stable folate derivatives 5-methyl-tetrahydrofolate (5 CH3 H4folate) and 10-formyl folic acid (10 HCO folic acid) in their monoglutamate forms were found using high performance liquid chromatography and mass spectrometry detection (LC/MS). The extraction procedure of MA was improved according to these findings, validated and used for analysis of the sampled eggs. There were no significant differences related to production form, the breed of hen or the feed used, organic or conventional. The retention factor for folate in boiled eggs was determined to 91 %. A method with a new technique, ultra performance liquid chromatography (UPLC) was developed. It was more sensitive and faster when compared with an HPLC method. Further comparison with the MA will show if this can be an alternative method for folate determination of foods.