BELFAST, Northern Ireland, July 23 (UPI) -- Researchers are suggesting people cook rice in a coffee maker instead of boiling it in a pan to reduce potentially harmful levels of arsenic in the food. 
 
 Rice contains on average 10 times more arsenic than other foods because it is grown in flood plains. This causes inorganic arsenic to be released by soil minerals, which are then absorbed by the plant. 
 
 "This is a very significant breakthrough as this offers an immediate solution to decreasing inorganic arsenic in the diet," said Andy Meharg, a professor of Plant and Soil Sciences at Queen's Institute for Global Food Security, in a press release. 
 
 Researchers sought a simple way to remove arsenic from rice by testing two types of percolating technology, one a normal store-bought coffee maker using tap water and the other using freshly hot distilled water recycled by condensing boiling-water steam. 
 
 Both methods removed up to 85 percent of arsenic depending on the type of rice. The steam method of percolating on average removed 59 percent of arsenic from white rice and 69 percent from whole grain rice. The store-bought filtration coffee maker removed and average of 49 percent of arsenic from samples of 6 white and 6 whole grain brands of coffee. 
 
 "We discovered that by using percolating technology, where cooking water is continually passed through rice in a constant flow, we could maximize removal of arsenic," Meharg said. "Chronic exposure to inorganic arsenic can cause a range of health problems including developmental problems, heart disease, diabetes and nervous system damage. However, most worrying are lung and bladder cancers." 
 
 The researchers said that children and infants were of most concern for arsenic poisoning because they eat about 3 times as much rice as adults, and their organs are still developing. 
 
 The study is published in PLOS ONE. 

 Abstract A novel way of cooking rice to maximize the removal of the carcinogen inorganic arsenic (As i ) is presented here. In conventional rice cooking water and grain are in continuous contact, and it is known that the larger the water:rice cooking ratio, the more As i removed by cooking, suggesting that the As i in the grain is mobile in water. Experiments were designed where rice is cooked in a continual stream of percolating near boiling water, either low in As i , or As i free. This has the advantage of not only exposing grain to large volumes of cooking water, but also physically removes any As i leached from the grain into the water receiving vessel. The relationship between cooking water volume and As i removal in conventional rice cooking was demonstrated for the rice types under study. At a water-to-rice cooking ratio of 12:1, 57±5% of As i could be removed, average of 6 wholegrain and 6 polished rice samples. Two types of percolating technology were tested, one where the cooking water was recycled through condensing boiling water steam and passing the freshly distilled hot water through the grain in a laboratory 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 approaches proved highly effective in removing As i from the cooking rice, with up to 85% of As i removed from individual rice types. For the recycled water experiment 59±8% and 69±10% of As i was removed, on average, compared to uncooked rice for polished (n=27) and wholegrain (n=13) rice, respectively. For coffee percolation there was no difference between wholegrain and polished rice, and the effectiveness of As i removal was 49±7% across 6 wholegrain and 6 polished rice samples. The manuscript explores the potential applications and further optimization of this percolating cooking water, high As i removal, discovery. 
 
 Citation: Carey M, Jiujin X, Gomes Farias J, Meharg AA (2015) Rethinking Rice Preparation for Highly Efficient Removal of Inorganic Arsenic Using Percolating Cooking Water. PLoS ONE 10(7): e0131608. https://doi.org/10.1371/journal.pone.0131608 Editor: J. Christopher States, University of Louisville, UNITED STATES Received: February 23, 2015; Accepted: June 2, 2015; Published: July 22, 2015 Copyright: © 2015 Carey et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited Data Availability: All relevant data are within the paper and its Supporting Information files. Funding: The authors received no specific funding for this work. Competing interests: The authors have declared that no competing interests exist. 
 
 Introduction Paddy rice is the carbohydrate staple of half the world yet is the main source of exposure to the class-one, non-threshold carcinogen inorganic arsenic (As i ) [1]. International and national bodies are in the process of setting standards for inorganic arsenic in rice due to the fact that sub-populations are exposed to levels that are associated with negative health consequences [2]. The UN WHO has just set, in 2014, advisory levels of As i in polished (i.e. white) rice grain at 0.2 mg/kg [3], while the European Union [2] and United States of America [4] are in the process of setting legal standards for inorganic arsenic in rice based products. It is highly desirable to reduce the inorganic arsenic content of rice. While breeding low arsenic rice and altering of rice cultivation practice offer medium to long-term solutions to reducing inorganic arsenic content of grain [5], if rice preparation to remove inorganic arsenic is optimized, this offers an immediate solution to decreasing inorganic arsenic in the diet. Milling, fortuitously for those who prefer polished (white rice), already reduces the inorganic arsenic content of rice by ~50% [6,7]. Bran is much more enriched (~10-fold) in As i compared to polished (white) rice [6,7], though the milled bran component is only ~10% of wholegrain biomass. However, the levels of As i in polished rice are still highly problematic [1,4,6,7]. The way that rice is cooked has been shown to have an effect on As i content. The now common way to cook boiled rice throughout the globe is to use a volume of water that will result in all the water being absorbed or evaporated. This does not cause loss of As i on cooking [8–10]. Where the cooking water itself is elevated in As i , such as in large tracts of Bangladesh, cooking further elevates the arsenic content of the cooked product [11]. Traditional S.E. Asian methods of rice cooking involved extensive rinsing of the uncooked grain followed by cooking the rice in a large excess of water and discarding that water on cessation of cooking and this was found to reduce As i content of food by up to 45% [10] and 57% [8] when As i free water was used. Steaming is another traditional cooking approach, where rice is not directly exposed to cooking water, but steaming can only remove up ~10% of As i [10]. In the study presented here rice cooking is radically rethought to optimize As i removal. It is demonstrated that percolating technology, where cooking water, either free off, or low in, As i is continually passed through rice in a constant flow, is highly efficient at removing As i . This cooking water percolation potentially maximizes the removal of As i , by both enhancing the volume of water the rice comes into contact with and by physically removing As i leached from the rice. A number of variations on percolation technology are trialed; one where the water percolated through the rice is recycled through distillation; and one where the perfused water is discarded. The former is suitable where cooking water is itself elevated in As i and/or where water is scarce or needs conserved, and the later suitable for low As i water sources. The proposed technology can be low-tech and to demonstrate this in a domestic setting an off-the-shelf coffee percolator was used to remove As i from wholemeal and polished rice. 
 
 Materials and Methods Rice sourcing Market rice was purchased from major UK retailers in the city of Belfast, or purchased online through UK retailers, i.e. all products tested were widely available to the UK populace. Of the 41 samples tested in this study 2 were generically labeled as being from the EU, 11 from Spain, 6 from Italy, 5 from Thailand, 5 from France, 2 from Egypt, 1 from Japan, 1 from Australia, 1 from Lebanon, 1 from Pakistan, 1 from Turkey and 5 from the USA; with 13 being unpolished (wholegrain) and the rest polished. Descriptions of samples are given in S1 Table. Cooking rice in different volumes of water Initial experiments investigated the relationship between cooking water volume and As i content. A standardized and repeatable approach was used where a 250 ml round bottomed Pyrex was used as the rice-cooking vessel. This was heated in an electrothermal heating mantle and the neck of the flask connected to a dimpled Vigreux 25cm condensing tube (14 rows of 3 dimples = 42 dimples in total) that returned steam as water to the flask. Evaporative losses as a confounding factor look in interpreting As i content of cooked rice and by condensing any evaporated steam back into the cooking vessel such losses are negated. Rice (20g packet weight), from 6 wholemeal and 6 polished randomly selected from the bought packets, was placed in the flask and then double-distilled, deionized water added to give 3:1, 6:1 or 12:1 water:rice ratios. Rice was boiled until cooked and then removed from the heat. After cooling the sample was freeze-dried and then powdered using a Retch PM100 rotary ball-mill using a zirconium oxide lined vessel and zirconium oxide grinding balls. Uncooked rice was similarly freeze-dried and milled. Cooking rice in where percolating cooking water is recycled through condensation Here all 41 samples of bought rice were cooked in a standard Soxhlet apparatus. Rice grain, fresh from the packet, was accurately weighed (2g) into a VWR Soxhlet thimble and was then placed into an 25cm long and 3.5cm diameter Quickfit Soxhlet which was attached to a 250ml receiving flask at one end and a dimpled Vigreux 25cm condensing tube (14 rows of 3 dimples = 42 dimples in total), with the receiving flask sitting within an electrically heated mantle and supported by a retort stand and clamps. At the start of the experiment the flask was filled with 200ml of double-distilled, deionized distilled water. Rice cooking was timed as per number of Soxhlet reflux cycles, with 3 cycles sufficient to fully cook the rice. At the end of the 3rd cycle the thimble containing rice was removed and rice freeze dried and milled as described for the cooking volume experiment. Home-cooking in a coffee percolator Six randomly chosen wholegrain and polished rice samples were cooked from the packet in a domestic environment, at quantities required to feed a large family, using an off-the-shelf coffee percolator with no adaptations. The coffee percolator chosen for these experiments was a catering model that is used to fill vacuum flasks, a Bravilor Bonamat. This type of percolator was used as it has a larger filter unit and it does not have a hotplate. Into the filter unit, lined with the manufacturers supplied paper filter, was placed 500g packet weight of the rice. The unit held 2L of water and this took 10 mins. to fully discharge through the filter unit. Twice times 10 mins. (i.e. 20 minutes of cooking) fully cooked polished rice, while 3 time 10 mins. (6L of water, i.e. 3* 2L) was needed for polished rice. Temperature of the water entering the filter was 98°C. The cooking experiments were conducted in triplicate for each rice type. The cooked rice was freeze dried and milled, as for other cooking experiments described above. Arsenic in the tap-water was low with only As i being detected, at 0.050±0.02 μg/L, with the LOD being 0.036 μg/L. Chemical analysis For As speciation powdered cooked and uncooked rice were weighed accurately to a weight of 0.1g into 50ml polypropylene centrifuge tubes to which 2ml of 1% conc. Aristar nitric acid was added and allowed to sit overnight. Batches of 40 samples were prepared which also include a black and rice CRM (NIST 1568b Rice flour) which has the arsenic species As i and dimethylyarsonic acid (DMA) concentrations certified, then microwave digested in an CEM MARS 6 instrument for 30 min. at 95°C using a 3 stage slow heating program: to 55°C in 5 min. held for 10 min., to 75°C in 5 min., held for 10 min. to 95°C in 5 min., held for 30 minutes. The digestate, on cooling, was accurately diluted to 10ml with deionized distilled water. A 1 ml aliquot was transferred to a 2ml polypropylene vial and 10 ul of analytical grade hydrogen peroxide was added to convert any arsenite to arsenate to facilitate subsequent chromatographic detection. For multi-element analysis by ICP-MS, a more aggressive digestion procedure (heat to 95°C in 5 min. hold for 10 min. to 135°C in 5 min. then hold for 10 min., to 180°C in 5 min. then hold for 30 min.) was employed, with 2ml of concentrated Aristar nitric acid and 2ml hydrogen peroxide added and left to soak overnight before microwaving. Blanks and CRM NIST 1568b, which is certified for both arsenic speciation (As i and DMA) and for a range of trace and macro elements, were included in each batch of 40 samples analysed. To speciate As in rice the diluted 0.2% nitric acid digested rice solutions were run on a Thermo Scientific IC5000 Ion Chromatography (IC) system, with an Thermo AS7, 2x250mm column (and a Thermo AG7, 2x50mm guard column) and a gradient mobile phase (A: 20mM Ammonium Carbonate, B 200mM Ammonium Carbonate- Starting at 100% A, changing to 100% B, in a linear gradient over 15 min.) interfaced with a Thermo ICAP Q ICP-MS that monitored m/z+ 75, using He gas in collision cell mode. The resulting chromatogram was compared with that for authentic standards; DMA, As i , monomethylarsinic acid (MMA), tetratmethyl arsonium (TETRA) and arsenobetaine (AB). Arsenic present under each chromatographic peak was calibrated using a DMA concentration series. Total elements were measured also using the Thermo ICAP Q but in direct solution acquisition mode. Rhodium was used as an internal standard. All elements reported were present both in calibration standards and in CRM NIST 1568b with only elements with good CRM recoveries reported. Additional elements were also analyzed by bench-top XRF (Rigaku CG) on powered samples. Only elements present in the CRM and with good analytical recoveries were presented. Statistics General Linear Modeling (GLM), using Minitab v.16, was used to analyze the data. Residuals were tested for normality using the Anderson-Darling test, and where found to be normal so no transformation of the data was needed, except for percentage data, which were ranked and the ranks analysed. 
 
 Discussion Mitigating As i levels in rice is essential as this commodity is the major global source of this carcinogen, with As i derived from rice consumption predicted to cause significant increases in excess lifetime cancer burdens, in the order of ~1–2 in 1,000, for the highest rice eating communities [1]. Using a continual flow of clean cooking water versus traditional static systems enables up to 85% of the As i content of raw grain to be removed on cooking, much higher than the use of standard static cooking water or steaming based systems [10]. Furthermore, this continual flow system offers a way of assaying which rice is amenable to have As i removed on cooking, and using a Soxhlet based system, the method is also standardized and repeatable in any laboratory and is not reliant on the purity of water used because delivery of cooking water is through distilled steam. Although the standardized cooking methods were developed around reflux/Soxhlet for standardization, household or commercial scale cookers could adopt the same approach as demonstrated here in the coffee percolator experiment. The development of commercial approaches based on continuously flushing rice with arsenic free cooking water would have application in baby rice manufacture, for example, as baby rice is of particular concern with respect to human exposures [12,13] and baby rice is a product where grain is pre-cooked, dried and milled, much the same as the sample preparation for analysis here. Rice milk is similarly problematic, being elevated in As i , and is fed to lactose intolerant children in quantities that raise concern [14]. Rice milk is prepared from cooked rice and manufacturing processes could be optimized for As i cooking using the continual cooking water flow principle demonstrated here. It is not difficult to envisage that large-scale rice cookers for baby rice and rice milk manufacture could be based either on the distillation approach, as demonstrated here by using a Soxhlet system, or with a continual flow of externally pre-heated water passing through the rice, as demonstrated here by the commercial coffee percolator approach. With baby rice if elemental nutrients (i.e. potassium) do need supplementation this is easy to do and, indeed, many baby rice products are nutrient and vitamin fortified. Vitamin removal was not assessed here and again may need to be investigated with respect to commercial production of products such as baby rice, and as rice is an important source of soluble B-vitamins [15], with vitamin B2 known to be leached from rice on cooking dependent on processing methodologies [16]. Non-milled, pre-cooked rice is becoming an important market in the prepared food business, from stand-alone precooked boiled rice to boiled rice in pre-packed Asian & S.E. Asian foods, and in products such as pre-cooked baby food jars. For all these products continual cooking water flow cooking approaches could be applied to lower As i to consumers. Cooked rice texture using continual flow cooking, not assessed here, while unimportant for milled baby rice, would be important for non-milled pre-cooked products, but manufactures could optimize rice type/source and cooking conditions to optimize final texture of their product. Home cooking continual flow would need the specific product design, but should be achievable, and given that there is already a wide penetrance of specific rice cookers for domestic use, based on steaming, so there is a market for specific rice cookers. We have demonstrated here that coffee percolator technology could also be used to cook rice, and that such technologies could be optimized for As i removal and, and to optimize the heat and water usage to most efficiently achieve this goal. The coffee percolator technology is most suitable for cooking rice in regions that have low As i available for the cooking water, although distilled/purified water could be directly used if in high water As i regions, if available. Where As i is high in cooking water then the recycling of water through continuous distillation is the solution. The key to a home based continual reflux distillation rice cooker development simply needs a steam condensers unit to supply water to rice suspended in a basket with a bottom receiver (pot) directly heating the water. Condensers could be based on water/ice cooling, on thermal properties of materials used for a lid with the design of the inside of the lid optimized to deliver stream of condensing water to the rice, or on electro-thermal cooling technologies for the lid/condenser. Home-based appliances for water/ethanol extraction of essential oils from plant-based material are already available [17] and could be readily adapted, to lower cost and to increase efficiency. In situ speciation [6] shows that grain As i is either as free As i or as sulfhydryl complexed As. It is not clear why grains with more As i release more As i on cooking as compared to those low in As i , but perhaps it is grain geometry, i.e. that As i in the outer portions of the grain are more easily removed than those in the inner portions. It is known that As i is more elevated at the grain surface than in the centre [6]. The finding that As i is readily leached from rice while DMA is not conforms well with what is known with their rice gut availability where As i has a high gut availability where DMA does not [18]. The fact that As i is readily leached from both wholegrain and polished rice is also important. Although not tested here, if rice bran As i is readily removed using continual flow of replenished cooking water then this product which is highly elevated in As i may be made suitable for the human food-chain, given that in many aspects it is a highly nutritious product whose health and commercial value is negated by its As i content. 
 
 Supporting Information Three additional graphs, pertaining to the DMA content of rice that complement the As i content of rice shown in S1–S3 Figs in the main body of the text. A table of rice sample descriptions is also given in S1 Table. S1 Fig. DMA concentration and percentage in rice that is either uncooked or has been cooked at different water: ratios. Squares are for wholegrain rice and circles for polished rice. Solid regression line is for wholegrain, dashed for polished. https://doi.org/10.1371/journal.pone.0131608.s001 (TIF) S2 Fig. DMA concentration and percentage in rice cooked using a Soxhlet apparatus compared to uncooked rice. Squares are for wholegrain rice and circles for polished rice. Solid regression line is for wholegrain, dashed for polished. https://doi.org/10.1371/journal.pone.0131608.s002 (TIF) S3 Fig. DMA concentration and percentage in rice cooked using a coffee percolator compared to uncooked rice. Each point is the mean of 3 replicates. Squares are for wholegrain rice and circles for polished rice. Solid regression line is for wholegrain, dashed for polished. https://doi.org/10.1371/journal.pone.0131608.s003 (TIF) S1 Table. Rice sample descriptions. https://doi.org/10.1371/journal.pone.0131608.s004 (DOCX) 
 
 Author Contributions Conceived and designed the experiments: MC AAM. Performed the experiments: MC XJ JGF. Analyzed the data: MC AAM. Wrote the paper: MC AAM. 

 Jacob Silberberg/Panos 
 
 Cooking rice by repeatedly flushing it through with fresh hot water can remove much of the grain’s stored arsenic, researchers have found — a tip that could lessen levels of the toxic substance in one of the world’s most popular foods. 
 
 Billions of people eat rice daily, but it contributes more arsenic to the human diet than any other food. Conventionally grown in flooded paddies, rice takes up more arsenic (which occurs naturally in water and soil as part of an inorganic compound) than do other grains. High levels of arsenic in food have been linked to different types of cancer, and other health problems. 
 
 Andrew Meharg, a plant and soil scientist at Queen’s University Belfast, UK, wondered whether cooking the grain in a different way might help to lessen the health risk. The standard method for making rice — boiling it in a pot until it soaks up all the liquid — binds into place any arsenic contained in the rice and the cooking water. 
 
 Percolation is key 
 
 On the basis of earlier work, Meharg and his colleagues knew that arsenic levels drop when rice is thoroughly rinsed and then cooked in an excessive amount of water. The method helps even when the cooking water contains arsenic. 
 
 Meharg and colleagues found that using this method with increasing proportions of water removed progressively more arsenic — up to a 57% reduction with a ratio of 12 parts water to one part rice. That result confirmed that the arsenic is 'mobile' in liquid water, and thus can be removed. 
 
 The team then cooked rice in an apparatus that continually condenses steam to produce a fresh supply of distilled hot water, and in an ordinary coffee percolator with a filter, which allows cooking water to drip out of the rice. Testing the rice before and after cooking showed that coffee-pot percolation removed about half the arsenic, and that the lab apparatus removed around 60–70%. In some cases, the technique removed as much as 85% of the substance, depending on the type of rice used. The findings are reported in PLoS ONE1. 
 
 Short-term fix 
 
 Meharg does not expect people to start cooking rice in their coffee machines. “We just took something that’s in everybody’s kitchen and applied it to show a principle,” he says. He sees the research as a proof of concept that could feed the development of simple, inexpensive rice cookers that lower arsenic concentrations. 
 
 The risk of arsenic poisoning is greatest for consumers who eat rice several times a day. In Bangladesh, where rice is a staple and the water is also naturally high in arsenic, people are particularly vulnerable. Parboiling facilities in the country process rice by pre-cooking, drying and husking the grain. These processes offer the opportunity to intervene on a commercial scale with cookers that would reduce arsenic levels — something that Meharg plans to do. 
 
 The same technique could also help companies elsewhere to lower arsenic levels in baby cereals and other products that use pre-cooked rice. Rice-based baby foods often contain high levels of arsenic2, a double-whammy for small children, who consume proportionately more of the substance for their body size. 
 
 In the long term, the best strategies for removing arsenic from rice will come from ongoing efforts to breed low-arsenic strains and alter growing techniques, says Margaret Karagas, an epidemiologist at Dartmouth College in Hanover, New Hampshire. But, she says, “This paper is really interesting because it is offering a short-term solution to the problem. It’s giving people an opportunity to reduce the arsenic burden of their rice.”
– High levels of arsenic in rice shouldn't scare you away, scientists say, because they've found a way to flush most of the toxin, the journal Nature notes. Researchers for the study in Plos One acquired 41 rice samples from at least a dozen countries and dumped them into either a lab-built contraption that condensed steam and produced fresh, distilled hot water or into a regular old coffee percolator with a filter, where the hot water dripped onto the uncooked rice (and then back out of the rice). The results: The coffee percolator-cooked rice got rid of half its arsenic, while the steam device got rid of up to 85% in some cases, depending on whether white rice or whole-grain rice was used, per the study. These findings could affect countries that consume lots of rice and even infants who eat rice-based cereals, as high arsenic levels in food have been tied to cancer. The way rice is produced contributes to why the product can have up to 10 times the arsenic levels of other foods: The water present in the flooded paddies where rice is grown can shake up inorganic arsenic found in the soil and infiltrate the plants, UPI reports. The study's leader notes this technique is simply a short-term fix for people who don't want to wait for longer-term solutions like revamping rice-growing processes and cultivating strains that contain low levels of arsenic, per Nature. He also doesn't expect everyone to start firing up their coffee machines whenever they want to make jambalaya—he's really hoping this method may lead to better rice-cookers down the road. "We just took something that's in everybody's kitchen and applied it to show a principle," he tells the journal. (Arsenic has been found in water, apple juice, and even beer.)