Iron, zinc and phytic acid content of selected rice varieties from China
2007
Liang, J. | Han, B.Z. | Han, L. | Nout, M.J.R. | Hamer, R.J.
Rice is the major Chinese staple food (per capita approx 250 g day-1) and, as such, is an important source of essential minerals. However, due to a number of factors the bio-availability of these minerals is limited. In this study, the variation of phytic acid (PA), iron (Fe) and zinc (Zn) levels in 56 varieties of Chinese rice was investigated. The samples included in this study were collected in proportion to the importance of the rice-growing regions in China. Fe levels showed the biggest variation (9-45 mg kg-1) and were not related with PA content or grain shape although growing locations were identified yielding higher (25.2 mg kg-1) and lower (14.2 mg kg-1) Fe levels. Zn showed a moderate variability (13-39 mg kg-1), which was narrower than for Fe, while broader than for PA (7.2-11.9 g kg-1). Zn content is correlated (R2 = 0.5; P < 0.01) with PA content, and shows a relation with growing region and kernel shape. Variation of PA content is the least among the three components. Molar ratios of PA to Fe and Zn ranged from 15 to 105 and 27 to 67, respectively. The results of the mineral contents and PA content can be interpreted in terms of expected bio-availability. This study shows that the mineral bio-availability of Chinese rice varieties will be <4%. Despite the variation in mineral contents, in all cases the PA present is expected to render most mineral present unavailable. We conclude that there is scope for optimisation of mineral contents of rice by matching suitable varieties and growing regions, and that rice products require processing that retains minerals but results in thorough dephytinisation.
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