And, according to the researchers' findings published in the International Journal of Food Science and Technology, levels of 225 mcg 100g -1 folic acid would be needed in flour to deliver commercial bread in Ireland with an average folic acid content of 120 mcg 100g -1, in line with requirements under a proposed mandatory bread fortification programme.
But any such fortification programme for flour with folic acid at a single mean target concentration will result in a diverse range of folic acid concentrations in bread and this, coupled with different bread consumption rates, would result in a wide variation in folic acid intakes, they concluded.
And the scientists further argue that such intakes would need to be monitored carefully to establish whether safety levels of folic acid are being exceeded in any sub-group and also whether optimal intakes were being achieved in women of women of child bearing age.
Folate deficiency in humans can lead to serious health conditions including neural tube defects (NTDs) in babies.
In 2005 the Irish government decided to examine the need for a mandatory programme of food fortification with folic acid to address the relatively high levels of NTDs in Ireland, with an expert committee recommending the mandatory fortification of bread to a level of 120 mcg 100g -1 to reduce the incidence of NTD-affected pregnancies by 24 per cent.
The authors claim there is no previous research of the effect of production on folic acid added to bread by fortification of flour during pilot scale production of the bread types that are commonly found on the Irish market, and they claim their results will help inform all countries considering a mandatory policy on such fortification of bread.
The researchers said fortification Ireland would be facilitated by the fact that the main supplier of flour to commercial bakeries has a 60 per cent share of the market, with the majority of the remaining flour used in these plants being sourced from the UK.
And they note that fortification programmes in other countries such as the US and Canada target the amount of folic acid added to flour with less consideration as to the final concentration of folic acid in the bread as consumed.
The heat degradation and overall reduction of folic acid during the bread baking were studied in four different wheat breads representing the main types of bread produced for the Irish market; white pan loaves, wholemeal pan loaves, white baguettes and brown soda bread.
Flour was fortified with different concentrations of folic acid and was used to make the four different types of bread.
The researchers found that bread type had an influence on the level of degradation of folic acid, noting a higher degradation in wholemeal pan loaves.
They found that folic acid degradation in white pan bread, white baguette and brown soda bread were similar at 23.6 per cent, 21.9 per cent and 25.7 per cent, respectively. However, folic acid degradation in wholemeal pan loaves was higher, at 31.1 per cent, added the authors.
“This difference was also observed in earlier pre-trials and cannot be explained by baking process differences which were similar for both white and wholemeal pan bread.
However, wholemeal flour has a number of constituents that differ from white flour. There are more nutrients in wholemeal flour which might make an oxidative degradation reaction more likely,” they explained.
The results, said the Irish researchers, also show that homogenisation of folic acid into flour preparations was not optimal and their findings raise questions as to the extent of even dispersion of folic acid in fortified flour that can be achieved on an industrial milling scale.
They said their findings also have implications for the variation of folic acid concentration in fortified bread.
Further work in this area, they said, will require monitoring of the folic acid content of the dough before baking to confirm homogeneity.
They also observed that the folic acid powder used in their trials had a tendency to clump, and the researchers said better dispersal of folic acid would be facilitated if it were finer and more free flowing.
Source: International Journal of Food Science and Technology
Published online ahead of print: 10.1111/j.1365-2621.2010.02226.x
Title: Reduction of folic acid during baking and implications for mandatory fortification of bread
Authors: W.A. Anderson, D. Slaughter, C. Laffey, C Lardner.