Analytical and Nutritional Aspects of Folate in Cereals

Johansson, M. 2005. Analytical and Nutritional Aspects of Folate in Cereals. Doctoral dissertation. ISSN 1652-6880, ISBN 91-576-7006-4 A good folate status before conception and during early pregnancy protects against child birth defects, particularly neural tube defects. According to dietary surveys, only a few percent of Swedish women reach the recommended daily intake of folate (400 μg). Swedish authorities are therefore discussing the introduction of mandatory folic acid fortification. A prerequisite for a decision is access to reliable data on folate in cereals since cereal food is both a major contributor to dietary folate intake and a common vehicle for fortification. Despite much progress in development of HPLC methods for folate, there is still a need for improved selectivity when analysing cereal samples with low level of folate. Ten silicabased stationary phases were compared and alkyl-bonded phases were found to be best for the separation of individual folate forms in terms of selectivity and peak shape. Best selectivity was achieved on an Aquasil C18 column. Optimising the sample purification prior to quantification can also improve the HPLC method. Reversed-phase sorbents, e.g. phenyl-endcapped and cyclohexyl-endcapped, were successfully used to purify folate from food extracts. By combining anion-exchange and reversed-phase sorbent, clean extracts of complex food samples were obtained. Several gluten-free products were analysed for folate content after deconjugation with rat serum using a validated HPLC method. Trienzyme treatment was found to be unnecessary for these samples. Gluten-free products contain considerably less folate than their glutencontaining counterparts and should be considered for folic acid fortification. Studies on stability of added folic acid during the baking procedure showed an overage of approximately 20% to be necessary to achieve targeted levels. Another important issue in deciding the appropriate fortification level is the extent to which the added folate is absorbed. In a short-term human study using volunteers with ileostomy, mean apparent absorption from folic acid-fortified bread was estimated to be 80%. In a 3-month intervention study, it was observed that a daily additional amount of 166 μg folic acid from fortified white bread was sufficient to significantly increase the folate status in women. Based on these two human studies it is concluded that bread is a suitable vehicle for folic acid fortification.