Investigating a fermentation process to reduce phytate levels in wholegrain bread

Abstract

Wholegrain is characterised by a high content of dietary fibre, B-vitamins, vitamin E and various minerals of which Mg, P, Fe, Cu and Zn are most important. These tend be concentrated in the outer layers of grains, as is phytate which is the principal storage form of phosphorus in cereals. The presence of this component has long been regarded as undesirable due to the antinutritional property of strongly binding divalent cations. The milling of grain to give white flours reduces the levels of many nutrients as well as phytate; however this component has also recently been recognized for a variety of possible benefits to human health including anti-cancer and anti-tumour roles. Sourdough has been used as the traditional fermentation over a long period of history but is now attracting considerable interest for wheat and rye as well as oat breads. The objective of the current research has been to investigate the inclusion of freshly ground wholegrain flour into bread formulations in conjunction with long term sourdough fermentation (5-7 hours) and the reduction phytate levels in the resultant products. This includes the optimisation of suitable fermentation conditions, including time and temperature. The phytate content has been determined by a spectrophotometric assay utilising the measurement of iron with 2, 2-bipyridine. The results indicate that temperature and time of the fermentation process are both important factors influencing phytate levels and hence mineral bioavailability. This has implications for human wellbeing as the potential benefits of wholemeal breads incorporating various grains are being realised.