Abstract
Inorganic arsenic (iAs) is a group 1 carcinogen, and consumption of rice can be a significant pathway of iAs exposure in the food chain. Although there are regulations in place to control iAs for marketed rice in some countries, additional measures are explored to remove arsenic from rice. Due to the surface-bound and soluble nature of iAs, previous studies have shown that it can be removed to a significant extent using different cooking methods. Towards this goal we modified and tested the absorption method in combination with four home-friendly cooking treatments (UA = unwashed and absorbed, WA = washed and absorbed, PSA = pre-soaked and absorbed, and PBA = parboiled and absorbed) using both brown and white rice (3 types each). The nutrient elements were measured using ICP-MS and arsenic speciation was carried out using LC-ICP-MS. Overall, our results show that PBA was the optimum approach assessed, removing 54% and 73% of inorganic arsenic (iAs) for brown and white rice respectively, raising the margin of exposure (MOE) by 3.7 for white rice and 2.2 times for brown rice, thus allowing the consumption of rice more safely for infants, children and adults. Other cooking treatments were effective in reducing the iAs concentration from white rice only. Here we also report changes in selected nutrient elements (P, K, Mg, Zn and Mn) which are relatively abundant in rice. In general, the treatments retained more nutrients in brown rice than white rice. No significant loss of Zn was observed from both rice types and the loss of other nutrients was similar or less than in comparison to reported losses from rice cooked in excess water in the literature. We conclude that PBA is a promising technique and further research is needed by including different regional rice types and water quality levels.
Highlights
Our results show that Parboiled and absorbed (PBA) was the optimum approach assessed, removing 54% and 73% of inorganic arsenic for brown and white rice respectively, raising the margin of exposure (MOE) by 3.7 for white rice and 2.2 times for brown rice, allowing the consumption of rice more safely for infants, children and adults
Though the above analysis was based on pooled data, in Fig. 2, we show the distribution of inorganic arsenic (iAs) and organic arsenic (oAs) in individual rice types (B1–B3; W1–W3) along with changes in their concentrations in response to cooking methods
PBA is practical to perform domestically, and was found to be the only method suited to all rice varieties in order to obtain a desirable MOE for all population groups
Summary
Please cite this article as: M. Menon, W. Dong, X. Chen, et al, Improved rice cooking approach to maximise arsenic removal while preserving nutrient elements, Science of the Total Environment, https://doi.org/10.1016/j.scitotenv.2020.143341macronutrients. However, rice can be a significant source of inorganic arsenic (iAs, comprised of AsIII and AsV), a poison and Group 1 carcinogen, according to the IARC (International Agency for Research on Cancer, 2012), when grown in an arsenic-contaminated environment (e.g. soil or water). Apart from iAs, rice also contains lower concentrations of less toxic organic arsenic (oAs) compounds such as dimethylarsenic acid (DMA), and traces of monomethylarsonic acid (MMA) (Bakhat et al, 2017; Islam et al, 2017).
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