Identification of possible technical problems in determination of the major inorganic constituents of brown-rice flour by evaluating proficiency test results.

To support skill upgrading in analysis of inorganic constituents of environmental and food samples, the National Metrology Institute of Japan (NMIJ) and the National Food Research Institute (NFRI) have organized a proficiency test (PT) of determination of Mn, Fe, Cu, Zn, As, and Cd in brown-rice flour based on the international standard (ISO/IEC 17043:2010). One hundred and thirty-three sets of reports were assessed by use of the E(n)-number and z-score approaches in accordance with ISO/IEC 17043 and the international harmonized protocol for PT. The PT results and analytical procedures, reported in detail, were reviewed, and possible technical reasons for questionable or unsatisfactory results are discussed.

Evidence for separate translocation pathways in determining cadmium accumulation in grain and aerial plant parts in rice.

BACKGROUND: Cadmium (Cd) translocation and accumulation in the grain and aerial plant parts of rice (Oryza sativa L.) is an important aspect of food safety and phytoextraction in areas with contaminated soil. Because control of Cd translocation and accumulation is likely to be determined by the plants genetics, the Cd contents of grain and the aerial parts of rice may be manipulated to improve food safety and for phytoextraction ability. This study studied Cd translocation and accumulation and their genetic control in aerial parts of rice to provide a starting point for improving food safety and phytoextraction in Cd-contaminated soils. RESULTS: In the japonica rice cultivar "Nipponbare", Cd accumulated in leaves and culms until heading, and in culms and ears after heading. Two quantitative trait loci (QTLs) from indica cv. "Kasalath", qcd4-1 and qcd4-2, affect Cd concentrations in upper plant parts just before heading. Three near-isogenic lines (NILs) with qcd4-1 and qcd4-2 were selected from the "Nipponbare" background, and were analyzed for the effects of each QTL, and for interactions between the two QTLs. From the results compared between "Nipponbare" and each NIL, neither QTL influenced total Cd accumulation in aerial parts at 5 days after heading, but the interaction between two QTLs increased Cd accumulation. At 35 days after heading, qcd4-2 had increased Cd accumulation in the aerial plant parts and decreased translocation from leaves other than flag leaf, but interaction between the two QTLs increased translocation from leaves. NILqcd4-1,2 accumulated higher concentrations of Cd in brown rice than "Nipponbare". CONCLUSION: Three types of Cd translocation and accumulation patterns demonstrated by NILs suggested that the accumulation of Cd in leaves and culms before heading, and translocation from them after heading are responsible for Cd accumulation in grain. Cd translocation from roots to culms and ears after heading may direct Cd to the aerial organs without influencing brown rice accumulation.

Effects of polishing, cooking, and storing on total arsenic and arsenic species concentrations in rice cultivated in Japan.

The effects of polishing, cooking, and storing on total arsenic (As) and As species concentrations in rice were studied adopting typical Japanese conditions. Total and inorganic As levels in three white rice samples polished by removing 10% of bran by weight were reduced to 61-66% and 51-70% of those in brown rice. The As levels in the white rice after three washings with deionized water were reduced to 81-84% and 71-83% of those in raw rice. Rinse-free rice, which requires no washing before cooking because bran remaining on the surface of the rice was removed previously, yielded an effect similar to that of reducing As in rice by washing. Low-volume cooking (water:rice 1.4-2.0:1) rice to dryness did not remove As. The As content of brown rice stored in grain form for one year was stable.

[Changes in the cadmium content of rice during the milling process].

Milled rice and bran were prepared from brown rice (Oryza sativa japonica) using a commercial scale rice-mill to investigate the changes in cadmium (Cd) content caused by the milling process. Rice sample solution was prepared by microwave digestion using HNO3 and HF, then analyzed by ICP-MS. Cd was measured at m/z 114 in interference correction with MoO and Sn. The digestion method was validated with 4 kinds of certified reference material of "rice flour". We found that the Cd content was reduced only slightly by the milling process. When the Cd concentration of brown rice was regarded as 100, the relative content of the milled rice was 97 (average of 6 samples). In addition, the reduction of the Cd content was only slight when milled rice was processed to "wash-free" rice. The relative Cd content of the bran was 139 when that of brown rice was regarded as 100. These results support the hypothesis that the Cd content is not greatly decreased by the milling process.