Grain mineral bioavailability

Fermentation of plant foods generally increases mineral bioavailability. Studies by Ranhotra and coworkers (121, 122 for example) have shown increased available zinc from breads and cookies that have undergone yeast fermentation. Also, iron was shown by these workers to be more highly available from unfortified breads than from breads fortified with wheat bran, soy flour or other whole grain vegetable flours. 

Phytate (myo-inositol hexaphosphate Fig. 15.3, structure 33) is found in many food species and can be considered as a phytochemical. Its role in the plant is primarily as a phosphate store in seeds, but it is found in other tissues as well, for example, tubers (Harland et al., 2004). Phytate and its hydrolysis products are anti-nutrients that chelate metal ions and thus reduce their bioavailability (Persson et al., 1998 House, 1999). This is particularly a problem with cereal grains, but pre-processing can improve mineral absorption from these foods (Agte and Joshi, 1997). There is some concern that high phytate foods could also contain higher levels of toxic heavy metals caused by natural accumulation. Plants also contain phytate-degrading enzymes that can also influence metal ion bioavailability (Viveros et al., 2000). 

An increase in consumption of whole grain flour products is one of the nutritional aims in Norway. The high content of dietary fiber or factors associated with it, however, present in bran and whole grain flour, may interfere with the bioavailability of minerals as suggested by several authors ( , 7, 8),... 

Phytic acid, phytates Phytic acid is a hexaphosphate ester of inositol, whereas phytates are phytic acid salts. Both store phosphorus for the critical event of germination. Phytates lower the bioavailability of minerals to monogastrics. Most phytates occur in the outer layers of cereal grains. 

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