N05060: A comparison of folate extraction procedures for the determination of folate in foods

Study Duration: February 2005 to October 2005

Contractor: Laboratory of the Government Chemist (LGC)

Classical extraction of folates has relied on heat treatment of the food followed by enzymatic hydrolysis with a &#947-glutamyl hydrolase (GGH) to make the folates available for assay. More recent analytical procedures have incorporated additional enzymes but results from these procedures are higher than previously claimed for many foods.

In 2002 and 2003, studies carried out at Ulster University showed significant and, in some cases, very substantial increases in the folate values for some foods compared to accepted values. They claimed that these increases were due to the use of the additional enzymes and also due to the use of a dual antioxidant protocol.

The first aim of this project is to determine whether the use of the 'trienzyme' extraction procedures and mixed antioxidants result in higher folate levels than the single enzyme procedures. The second aim is to determine whether the considerable increase in some folate levels claimed in the Ulster University studies could be substantiated, and whether these were due to the use of the trienzyme procedures. The final aim is to consider whether currently accepted values for folates in foods as used in food tables, are underestimated.

Five foodstuffs representing the major sources of folate in the UK diet are studied. In addition, a yeast control material and three certified reference materials are used as reference samples.

The test foods are analysed using the analytical procedures used at LGC (with GGH derived from chicken pancreas) and at Ulster University (with GGH derived from rat plasma). In both cases, extracts are analysed after simple heat treatment, after single GGH deconjugation and after trienzyme hydrolyses with amylase, protease and GGH enzymes. Analysis is carried out using microbiological assay.