Manoj Menon, Wanrong Dong, Xumin Chen, Joseph Hufton, Edward J Rhodes

Sci. Total Environ. 2021 Feb 10;755(Pt 2):143341.  doi: 10.1016/j.scitotenv.2020.143341.

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.

See https://pubmed.ncbi.nlm.nih.gov/33153748/

Figure 1: (a–d). Comparison of average inorganic As (a) and organic As concentrations (a, b) and in per cent (c, d) in brown and white rice under different cooking treatments (R = raw rice; UA = unwashed and absorbed; WA = washed and absorbed; PSA = pre-soaked and absorbed and PBA = parboiled and absorbed). Each bar represents the average of three rice samples (brown or white) with three replicates. The error bars indicate standard error of means (SEM). Note that in c & d, R was assumed to be 100% (hence no error bars) and all other treatments were normalised to R.