Folates in Berries Evaluation of an RPBA method to study the effects of cultivar, ripeness, storage and processing

Strålsjö, L. 2003. Folates in berries – evaluation of an RPBA method to study the effects of cultivar, ripeness, storage and processing. Doctoral dissertation ISSN 1401-6249, ISBN 91-576-6197-9 Folate concentrations in berries and berry products were investigated, determining folate retention from raw material to the final product. Folate content was quantified using a modified and systematically evaluated radioprotein-binding assay (RPBA). The optimised RPBA was demonstrated to be a useful method for folate quantification in berries containing mainly 5-CH3-H4folate. Results after internal evaluation regarding selectivity, background radiation, unspecific binding, and accuracy are presented. To avoid unspecific binding purification of sample extracts by solid phase extraction prior to quantification was included for some berries. Microbiological assay (MA) and high performance liquid chromatography (HPLC) were used to compare obtained folate concentrations and to characterise individual folate forms in tested matrices. The predominating folate form in all tested berries was 5-CH3-H4folate. Therefore, the recently commercially available natural form (6S)-5-CH3-H4folate was chosen as calibrant