Journal Article 1 Mention
Improved rice cooking approach to maximise arsenic removal while preserving nutrient elements
Manoj Menon•2020
Wanrong DongXumin Chen
Top 8% · 92nd Percentile
59 citations · Environmental Chemistry
Open AccessSTFC Food Network+ ExtensionSTFC Food Security Network+STFC Food Network+ Extension

TLDR

Pre-boiling rice before cooking removed much of its harmful arsenic while keeping most useful minerals. This method worked best for both brown and white rice, especially white rice.

Summary

1 Study Aim

The authors aimed to test household cooking methods that remove inorganic arsenic (arsenic forms linked to health risks) from rice while preserving nutrients. They focused on a modified absorption method, where rice cooks in a measured amount of water. The study compared washing, soaking, and pre-boiling before absorption cooking. The researchers wanted to identify the safest practical approach without causing unnecessary nutrient loss.

2 Study Design

The researchers tested three brown-rice types and three white-rice types. They compared four treatments: unwashed and absorbed, washed and absorbed, pre-soaked and absorbed, and pre-boiled and absorbed. They measured nutrient elements using inductively coupled plasma mass spectrometry (ICP-MS), an instrument that measures elements. They identified arsenic forms using liquid chromatography ICP-MS (LC-ICP-MS), which separates and measures those forms. The study compared how each household method changed arsenic and selected nutrients in both rice groups.

3 Findings

The study found that pre-boiling followed by absorption cooking was the best tested method. It removed 54% of inorganic arsenic from brown rice and 73% from white rice. The margin of exposure (MOE), a comparison showing how much safer exposure becomes, increased 2.2 times for brown rice and 3.7 times for white rice. Other treatments reduced inorganic arsenic only in white rice. Brown rice generally retained more phosphorus, potassium, magnesium, zinc, and manganese than white rice. Zinc showed no significant loss, while other losses were similar to, or smaller than, losses reported for cooking with excess water. The authors recommend testing more rice regions and water qualities. Pre-boiling before cooking removed the most harmful substance while keeping useful minerals fairly well.

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.

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