Mineral Content Analysis of Rice Flour

Dried seeds of each line were de-hulled, polished and then milled into flour, according to the surging and grind-milling method described in our previous report (Xu et al., 2015 (link)), to prevent possible mineral contamination, especially by Fe. About 0.3 g of rice flour was digested with 6 ml of HNO₃ and 0.2 ml of H₂O₂ using a microwave digestion system (Microwave300, Anton PAAR, Graz, Austria), with the following parameters: 5 min at 700 W, 700–1,200 W for 10 min, and 1,200 W for 20 min. The samples were then transferred to a block heater at 160°C for further digestion. The remaining 1 ml of digested sample was diluted with 50 ml of Milli-Q water before analysis. The Fe, Zn, Cd, Mn, Cu, and Se concentrations in the digested samples were determined using the methods described in our previous report (Xu et al., 2015 (link)). Two standards and two controls were set in each testing batch. Three replications of the tests were performed for each sample.