Calcium - Function and effects

Rice is the primary food source for more than half of the world population. Levels of calcium contents and inhibitor - phytic acid are summarized in this chapter. Phytic acid has a very strong chelating ability and it is the main inhibit factor for calcium in rice products. Calcium contents in brown rice varied with varieties and cultivation locations; white rice contains lower levels of calcium than brown rice caused by loss during milling. Levels of calcium in rice products mainly are due to processing and/or materials used. Calcium solubility in rice products can be improved by a decrease or degradation of phytic acid. Calcium and phytic acid distributed unhomogeneous in rice kernel. Most of the calcium locates in the bran part and more than 70% phytic acid locates in less than 8% of the outermost layer of rice kernel. Soaking, germination and treatment with phytase could degrade phytic acid. Calcium nutrition of rice products could be improved by supplementation, fortification and enhancers.