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UBC Theses and Dissertations

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UBC Theses and Dissertations

An in vitro estimation of relative iron availability from wheat bran Pegg, Deborah Lynn


The effects of baking, bran particle size and other meal components on the relative availability of the endogenous iron of wheat bran were investigated using an in vitro method. The method simulated gastrointestinal digestion and measured soluble, low molecular weight iron as an estimate of available iron. The wheat bran was incorporated into a muffin product to simulate a common domestic vehicle for fiber consumption. The muffins were blended to a slurry, adjusted to pH 2 and incubated with pepsin. Dialysis was used to adjust the pH to intestinal levels and digestion was continued with the addition of pancreatin and bile extract. Then iron from the digestion mixture which had diffused across a semipermeable membrane (6000 to 8000 molecular weight cutoff) was quantified as percent dialyzable iron. It was found that under the conditions of the in vitro estimation, essentially no iron was available from the bran when the muffins were combined with water. When the muffins were combined with orange juice there was a very significant enhancement of iron availability. The influence of orange juice was evaluated by comparing the relative effects of constituent organic acids. Muffins were blended to a slurry with aqueous solutions containing either ascorbic acid, citric acid or a combination of ascorbic and citric acids in amounts assumed to be present in orange juice. Combination with ascorbic and citric acids together showed significantly greater enhancement of iron availability from wheat bran than citric acid alone which produced significantly more dialyzable iron than ascorbic acid alone. However, the increase in available iron produced by the combination of constituent organic acids was only about half of that produced by orange juice. It was also found that bran particle size had no significant effect on relative iron availability under the conditions of this study. As well, it was determined that there was a significant decrease in iron availability due to baking. Finally, the results of this study indicated that further research is necessary to examine the chemistry of iron and iron binding as related to the availability of iron from wheat bran.

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