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Researchers propose an improved cooking recipe to reduce worrying levels of arsenic in our rice


Rice is often grown in paddies under flooded conditions, because the rice plant is tolerant of water and the water in the paddies prevents weeds from overtaking the seedlings. Once the crop is grown, the water is drained so it can be harvested. While the paddy system increases productivity, it is this flooding that releases inorganic arsenic, normally bound to soil minerals, which is then absorbed by the plant. Rice grown under such conditions has, typically, ten times more inorganic arsenic than other foods.

According to the European Food Standards Authority, people who eat a lot of rice, as is the case in many parts of the developing world, are exposed to worrying arsenic concentrations. Especially inorganic arsenic is associated with a range of health problems including, developmental problems, heart disease, diabetes and nervous system damage. However, most worrying are lung and bladder cancers. Children and infants are of particular concern as they eat, relatively, three times more rice than adults – baby rice being a popular food for weaning – and their organs are still developing (see the EVISA news).

The new study:

photo of rice, white, long-grain
Foto: Rice, white, long-grain, raw
Takeaway, CC BY-SA
It was already known that the mode of cooking has an influence on its final arsenic content (see the EVISA news). Researchers from Aberdeen (UK) had found that arsenic content can be reduced by 35-45 % by cooking rice with relatively high amount of water. In this new study, researchers at Queen’s tried to optimize the cooking procedure with respect to reduce the final arsenic content.  They tested two methods of percolating technology, one where the cooking water was recycled through condensing boiling-water steam and passing the freshly distilled hot water through the grain in a lab setting, and one where tap water was used to cook the rice held in an off-the-shelf coffee percolator in a domestic setting. Both method proved highly effective, with up to 85% of arsenic removed from a variety of different rice types and brands, including wholegrain and white.

This finding is significant both for industrial food processing such as baby food production as well as home kitchen cooking. Queen’s is at the patent stage for the development of a bespoke rice cooker based on a percolation system which means consumers could soon have this technology in their own kitchen.

Source: Adapted from Queen's University Belfast

The original study

Manus Carey, Xiao Jiujin, Júlia Gomes Farias, Andrew A. Meharg, Rethinking Rice Preparation for Highly Efficient Removal of Inorganic Arsenic Using Percolating Cooking Water, PLoS ONE 10/7 (2015) e0131608. doi: 10.1371/journal.pone.0131608

Analytical instrumentation:

Thermo Scientific iCAP Q ICP-MS
Thermo Scientific IC5000 Ion Chromatography (IC) system

Related studies (newest first)

Shigehiro Naito, Eri Matsumoto, Kumiko Shindoh, Tsutomu Nishimura, Effects of polishing, cooking, and storing on total arsenic and arsenic species concentrations in rice cultivated in Japan, Food Chem., 168 (2015) 294–301. doi: 10.1016/j.foodchem.2014.07.060

M. Azizur Rahman, H. Hasegawa, High levels of inorganic arsenic in rice in areas where arsenic-contaminated water is used for irrigation and cooking, Sci. Total Environ., 409 (2011) 4645–4655. doi:10.1016/j.scitotenv.2011.07.068

Victor G. Mihucz, Geert Silversmit, Imre Szalóki, Björn de Samber, Tom Schoonjans, Eniko Tatár, László Vincze, István Virág, Jun Yao, Gyula Záray, Removal of some elements from washed and cooked rice studied by inductively coupled plasma mass spectrometry and synchrotron based confocal micro-X-ray fluorescence, Food Chem., 121 (2010) 290–297. 

K. Ohno, Y. Matsuo, T. Kimura, T. Yanase, M.H. Rahman, Y. Magara, T. Matsushita, Y. Matsui, Effect of rice-cooking water to the daily arsenic intake in Bangladesh: results of field surveys and rice-cooking experiments, Water Sci. Technol., 59/2 (2009) 195-201. doi: 10.2166/wst.2009.844

Andrea Raab, Christina Baskaran, Jörg Feldmann, Andrew A. Meharg,  Cooking rice in a high water to rice ratio reduces inorganic arsenic content, J. Environ. Monit., 11 (2009) 41-44. doi: 10.1039/b816906c

Andrea Raab, Jörg Feldmann, A.A. Meharg, Levels of Arsenic in Rice: the effects of cooking, Report #C01049,  Foods Standard Agency (UK), 2009, pp. 27. Available from FSA

Silvia Torres-Escribano, Mariana Leal, Dinoraz Vélez, Rosa Montoro, Total and Inorganic Arsenic Concentrations in Rice Sold in Spain, Effect of Cooking, and Risk Assessments, Environ. Sci. Technol., 42/10 (2008) 3867-3872. doi: 10.1021/es071516m

A. Signes, K. Mitra, F. Burloacute, A.A. Carbonell-Barrachina, Effect of cooking method and rice type on arsenic concentration in cooked rice and the estimation of arsenic dietary intake in a rural village in West Bengal, India, Food Addit. Contam. Part A, 25/11 (2008) 1345-1352. doi: 10.1080/02652030802189732

Victor G. Mihucz, Eniko Tatár, István Virág, Chen Zang, Yun Jao, Gyula Záray, Arsenic removal from rice by washing and cooking with water, Food Chem., 105/4 (2007) 1718-1725. doi:10.1016/j.foodchem.2007.04.057

M.K. Sengupta, M.A. Hossain, A. Mukherjee, S. Ahamed, B. Das, B. Nayak, A. Pal, D. Chakraborti, Arsenic burden of cooked rice: Traditional and modern methods, Food Chem. Toxicol., 44/11 (2006) 1823-1829. doi:10.1016/j.fct.2006.06.003

M. Azizur Rahman, H. Hasegawa, M. Arifur Rahman, M. Mahfuzur Rahman, M.A. Majid Miah, Influence of cooking method on arsenic retention in cooked rice related to dietary exposure, Sci. Total Environ., 370 (2006) 51–60. doi: 10.1016/j.scitotenv.2006.05.018

José Moisés Laparra, Dinoraz Vélez, Reyes Barberá, Rosaura Farré, and Rosa Montoro, Bioavailability of Inorganic Arsenic in Cooked Rice: Practical Aspects for Human Health Assessment, J. Agri. Food Chem., 53/22 (2005) 8829-8833. doi: 10.1021/jf051365b

M. Bae, C. Watanabe, T. Inaoka, M. Sekiyama, N. Sudo, M.H. Bokul, R. Ohtsuka, Arsenic in cooked rice in Bangladesh, Lancet , 360 (2002) 1839-1840. doi:10.1016/S0140-6736(02)11738-7

Related information:

Consumer Reports: How much arsenic is in your rice ?
US FDA: Arsenic in rice and rice products
UK Food Standards Agency: Arsenic in Rice
WHO: Arsenic fact sheet

Related EVISA Resources

Brief summary: ICP-MS: A versatile detection system for speciation analysis
Brief summary: LC-ICP-MS - The most often used hyphenated system for speciation analysis
Brief summary: Standard methods for arsenic speciation analysis
Brief summary: Chemical speciation analysis for nutrition and food science
Link database: Arsenic species and human health/nutrition/metabolism

Link database: Toxicity of arsenic species
Material database: Rice reference materials
Material database: Reference materials for arsenic speciation

Related EVISA News (newest first):

November 14, 2013: Arsenic Speciation in Rice Cereals for Infants
May 15, 2013: Arsenic species in rice: Origin, uptake and geographical variation
February 15, 2013: JRC-IRMM has released ERM-BC211 certified rice reference material for arsenic speciation analysis
September 21, 2012: Arsenic in Rice : First results from the U.S. Food and Drug Administration
January 4, 2011: Arsenic species in rice: Call for analytical laboratories
May 19, 2010: China: Inorganic Arsenic in Rice - An Underestimated Health Threat ?
December 4, 2009: EFSA: Scientific Opinion on Arsenic in Food
May 26, 2009: UK Food Standards Agency releases research on arsenic in rice milk
January 31, 2009: Using the right recipe for cooking rice reduces toxic inorganic arsenic content
July 18, 2008: Experts detail how rice absorbs arsenic from the soil 
March 15, 2008: Arsenic in rice milk exceeds EU and US drinking water standards
February 15, 2008:
Arsenic speciation in rice: a question of the rice plant species
December 26, 2007: The effect of thermal treatment on the arsenic speciation in food
March 7, 2007: Elevated Arsenic Levels Found In Rice Grown In South Central States of the USA
September 7, 2006: New Agilent HPLC column for routine determination of arsenic species in human urine by HPLC-ICP-MS
August 3, 2005: Surprisingly high concentrations of toxic arsenic species found in U.S. rice

last time modified: July 26, 2015


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