Abstract

Folate content in berries and the effect of cultivar on folate content in strawberries were investigated using a modified radioprotein-binding assay (RPBA) combined with solid phase extraction (SPE). With an SPE step prior to quantification the matrix effects in the RPBA assay were minimised. HPLC quantification was used to compare and characterise individual folate forms. High correlation (r=0.9796) was shown and the mean difference between the RPBA and HPLC method was 6.7+/- 4.8 mikrogram/100g. The predominating folate form was 6S-5-CH3-H4folate in all tested berries (>95%). therefore, this biologically active form (6S-5-CH3-H4folate) must be chosen as calibrant because the RPBA response of the synthetic equimolar mixture of R- and S-diastereoisomers (6R,S-5-CH3-H4folate) was considerably higher, about 30%. The folate content in 9 selected Swedish berries varied from 11 to 96 mikrogram/100 g (fresh weight) and the highest folate content was found in rose hips (96 mikrogram/100g) and strawberries (74 mikrogram/100g). Moderate folate sources were raspberry (46 mikrogram/100g) and sea buckthorn (39 mikrogram/100g), whereas all other tested berries contained about 20 mikrogram of folate/100 g or less. In strawberries, folate content varied significantly among 8 different cultivars from 73 mikrogram/100g (Lina) to 99 mikrogram/100g (Melody)

Keywords

folate; radioprotein-binding assay; berries; strawberries; food analysis; method evaluation

Published in

European Food Research and Technology
2003, volume: 216, pages: 264-269

Authors' information