Effects of aqueous soaking on the phytate and mineral contents and phytate:mineral ratios of wholegrain normal sorghum and maize and low phytate sorghum

Abstract

Soaking of cereal grains has been suggested as a method to reduce their phytate content and hence increase their mineral availability. Whole and milled wholegrain, normal and low phytate sorghum and normal maize were studied. Soaking of unmilled sorghum and maize did not result in substantial reductions in phytate or mineral contents. With milled grains, phytate solubilisation was somewhat greater in maize than in sorghum after a short (1 h) soaking period but not after 6–12 h of soaking when practically all phytate had been solubilised. Also, with milled, low phyate sorghums, phytate solubilisation was not substantially higher than in their null controls. Soaking milled grain substantially reduced mineral contents and Ca × phytate:zinc molar ratios. However, the loss in soluble minerals could have a greater negative effect on mineral availability, compared to the positive effect of the phytate reduction. Thus, soaking does not seem to be a viable household method to improve sorghum and maize mineral availability.

• Calcium
• household method
• iron
• magnesium
• mineral availability
• phosphorus
• zinc

Acknowledgements

University of Pretoria post-doctoral fellowship for J Kruger. UIS Analytical services (Centurion, South Africa) for the ICP-OES analysis.