Dephytinisation of wheat bran and the consequences for fibre matrix non-starch polysaccharides
1997
Jayarajah, C.N. | Tang, H.R. | Robertson, J.A. | Selvendran, R.R.
Wheat bran is a rich source of dietary fibre. Modified milling technologies can yield fibre-enriched bran fractions but the processing also leads to a concentration of phytate, which has a perceived detrimental effect on mineral metabolism. Endogenous phytase activity in wheat grain can be used to reduce phytate levels, and methods to optimise phytase activity have been investigated using aleurone-enriched and pericarp-enriched bran fractions. It was found that dephytinisation of wheat bran could he achieved at a relatively low moisture content for each fraction. The extent of dephytinisation could be controlled either through control of moisture content or through time of incubation. By using yeast, the rate of dephytinisation at 35 degrees C was similar to that achieved by endogenous phytase alone at 55 degrees C. The endogenous phytase activity resulted in the destruction of phytate without accumulation of inositol phosphate intermediates, as monitored using 31P-NMR spectroscopy. Also, at low moisture levels there was no apparent modification of fibre components through polysaccharidase activities which may he present in the bran. Therefore bran fractions can be readily dephytinised at low moisture contents and without modification of the fibre components.
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