Distribution of Radioactive Cesium (134Cs Plus 137Cs) in Rice Fractions During Polishing and Cooking

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Journal of Food Protection, Vol. 78, No. 3, 2015, Pages 561–566 doi:10.4315/0362-028X.JFP-14-275 Copyright G, International Association for Food Protection

Distribution of Radioactive Cesium (134Cs plus 137Cs) in Rice Fractions during Polishing and Cooking

MAYUMI HACHINOHE, TOMOYA OKUNISHI, SHOJI HAGIWARA, SETSUKO TODORIKI, SHINICHI KAWAMOTO, AND SHIOKA HAMAMATSU*

National Food Research Institute, National Agriculture and Food Research Organization, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan Downloaded from http://meridian.allenpress.com/jfp/article-pdf/78/3/561/1683662/0362-028x_jfp-14-275.pdf by guest on 26 September 2021

MS 14-275: Received 10 June 2014/Accepted 12 September 2014

ABSTRACT We investigated the distribution of cesium-134 (134Cs) and cesium-137 (137Cs) during polishing and cooking of rice to obtain their processing factors (Pf) and food processing retention factors (Fr) to make the information available for an adequate understanding of radioactive Cs dynamics. Polishing brown rice resulted in a decreased radioactive Cs concentration of the polished rice, but the bran and germ (outer layers) exhibited higher concentrations than brown rice. The Pf values for 100% polished rice and outer layers ranged from 0.47 to 0.48 and 6.5 to 7.8, respectively. The Fr values for 100% polished rice and outer layers were 0.43 and 0.58 to 0.60, respectively. The distribution of radioactive Cs in polished rice and outer layers was estimated at approximately 40 and 60%, respectively. On the other hand, cooked rice showed significantly lower levels of radioactive Cs than polished rice, and transfer of radioactive Cs into wash water was observed. The Pf and Fr values for cooked rice were 0.28 and 0.65 to 0.66, respectively. From these results, we can calculate that if the radioactive Cs concentration in brown rice is 100 Bq/kg, the concentrations of Cs in polished rice and cooked rice will be 47 to 48 Bq/kg and 13 Bq/kg, respectively.

Rice is a staple food of Japan. Approximately 8 million products. If any sample exceeds the standard limit, all food tons of rice is harvested in Japan each year, of which more from the same lot is recalled and disposed of under the Food than 90% is consumed domestically (11). On 11 March Sanitation Act (14). Radioactive substances in domestically 2011, a large earthquake, the Great East Earthquake, produced foods are monitored in this way and controlled occurred which caused damage to a nuclear power plant rigorously. in Fukushima Prefecture. This resulted in leakage of Proper risk management for food safety requires not radioactive substances from the plant, which moved out only monitoring food contamination but also an under- into Fukushima Prefecture and surrounding areas (1, 20). standing of radioactive Cs dynamics during processing and This brought about the contamination of a wide range of cooking procedures that are widely used by the food foods by radioactive substances (mainly cesium-134 [134Cs] manufacture industry. The concentration of 137Cs in brown and cesium-137 [137Cs]). Based on the ‘‘Conception of rice is higher than that of polished rice (19), and 133Cs, Inspection Planning and the Establishment and Cancellation 134Cs, and 137Cs have been reported to be removed by of Items and Areas to which Restriction of Distribution and/ polishing and water washing of rice (15, 17, 18). However, or Consumption of Foods Concerned Applies’’ presented by the dynamics of radioactive Cs through a sequence of the Nuclear Emergency Response Headquarters on 4 April operations from polishing to cooking was not investigated 2011, the local governments surveyed have been monitoring before. This study was done to examine the distribution of for radioactive Cs (14). 134Cs and 137Cs during the polishing and cooking of rice 137Cs is reported as an important radionuclide for the (Oryza sativa cv. Koshihikari) using a standard polishing assessment of radiation exposure to the public because of its method and a family-size rice cooker in Japan, and it high fission yield, relatively long half-life, high transfer- provided the processing factors (Pf) and food processing ability, and wide distribution in the environment (16, 19, retention factors (Fr) as important criteria for product 21). For the monitoring of this food contaminant, radioac- control at food manufacturing establishments. tive Cs (134Cs plus 137Cs) is also a target nuclide. The standard limit for radioactive Cs in food in general, 100 Bq/ MATERIALS AND METHODS kg, was enforced as of 1 April 2012 (13). The level for food Rice grain samples. Brown rice grains, O. sativa L. cv. in general applies to both commodities and finished food Koshihikari, were harvested in autumn 2011 in Fukushima Prefecture, Japan. Koshihikari is a leading japonica rice cultivar * Author for correspondence. Tel: z81-29-838-7325; Fax: z81-29- in Japan. The rice samples, in Kraft paper bags (30 kg), were 838-8122; E-mail: [email protected]. manually uniformly premixed before the study. The uniformity of 562 HACHINOHE ET AL. J. Food Prot., Vol. 78, No. 3 the radioactivity of brown rice in the bags was confirmed using a distilled water used in this study had no detectable 134Cs (detection germanium semiconductor detector before the examination. limit, 0.07 Bq/kg), 137Cs (detection limit, 0.07 Bq/kg), or potassium- 40 (detection limit, 1.5 Bq/kg). Rice polishing. Two kilograms of brown rice was passed through a test milling machine (VP-31T, Yamamoto Co. Ltd., Moisture content analysis. Brown rice and polished rice Yamagata, Japan) under different conditions, varying the degree of were ground with a laboratory mill (Millser, Iwatani, Tokyo, Japan) whiteness and flow rate and number of times through the machine, to and dried at 135uC for 3 h. The moisture content was calculated as remove rice bran and germ. The polishing ratios used in the study the mass difference before and after drying. Each sample was were 0% (mass ratio of polished rice to brown rice, 0%), 30% (mass assayed in duplicate, and the average value was taken. In cooked ratio of polished rice to brown rice, 96.5 to 97.3%), 50% (mass ratio rice, the moisture content was derived from the mass and moisture of polished rice to brown rice, 92.2 to 95.6%), 70% (mass ratio of content of the polished rice and the mass of the cooked rice. polished rice to brown rice, 92.1 to 94.0%), and 100% (mass ratio of polished rice to brown rice, 90.8 to 91.3%). The condition of being Statistics. The arithmetic means with standard errors polished was verified by dyeing with New May-Gru¨nwald reagent calculated for the three replicate samples were taken as the (Wako, Osaka, Japan), which stains bran and endosperm in blue and radioactive Cs concentrations in brown rice, polished rice, bran, Downloaded from http://meridian.allenpress.com/jfp/article-pdf/78/3/561/1683662/0362-028x_jfp-14-275.pdf by guest on 26 September 2021 pink, respectively. The reagent was diluted by methanol. Each grain germ, aleuron layer, wash water, and cooked rice. The concentra- sample was soaked in the solution for 2 min with shaking. Dyed tions and Pf and Fr values were analyzed for significance with a grains were washed with milli-Q water three times and dried. Images Tukey’s test or t test using Microsoft Excel 2010 (Microsoft, were obtained with a digital high-resolution microscope (VH-5910, Redmond, WA) with the add-in Excel Statistics 2010 (Social Keyence Corp., Osaka, Japan) equipped with a VH-Z75 zoom lens. Research Survey Information Co. Ltd., Japan). Rice polishing was conducted in triplicate for each polishing ratio independently (n ~ 3). RESULTS Concentrations of radioactive Cs in polished rice Separation of rice bran and germ. Rice bran and germ were separated by a test sieve (850 mm; Tokyo Screen Co. Ltd., Tokyo, and bran during rice polishing. Brown rice consists of Japan) into upper and lower portions. The upper portion, which bran (pericarp, tegmen, and aleuron layers), germ, and an remained on the sieve, was the germ, and the lower portion, (the) endosperm (9). In the rice milling operation, the bran passing through the sieve, was the bran, including the pericarp, and germ (outer layers) were polished away to produce the tegmen, and aleuron layers. The separation was repeated in edible portion (endosperm) for human consumption. A triplicate independently (n ~ 3). friction-type milling machine was used in this study; friction-type milling is the primary procedure used to supply Preparation of cooked rice. A colander was placed that fit rice for food, especially for japonica-type rice (8). There are completely into a bowl about 25 cm in diameter and 13 cm in four ratios of rice polishing, 30, 50, 70, and 100%, used for depth, and 800 g of 100% polished rice grains was placed in the domestic consumption in Japan. The mass ratios of polished double vessel. Water (900 g) was added to the bowl and mixed for 30 s with a whisk. The colander was lifted, and the water was rice from brown rice for these polishing types are described in recovered as the first washing. The colander was returned to the ‘‘Materials and Methods.’’ Changes in the radioactive Cs empty bowl, and rice washing was carried out four more times, concentrations in polished rice and the outer layers of the using 800 g of water each time. All rinse water was recovered. To polishing types are shown in Figure 1A and 1B, respectively. the washed rice, 1,200 g of water, including the amount of water Two brown rice samples, K1 and K2, with different absorbed during washing, was added. The rice was cooked in a rice concentrations of radioactive Cs were used in this study. cooker (NH-WA18, Zojirushi Corporation, Osaka, Japan). The The radioactivity concentrations of Cs in brown rice samples preparation was conducted in triplicate independently (n ~ 3). K1 and K2 were recorded as 83 and 145 Bq/kg, respectively. The concentrations of radioactive Cs in polished rice were Radioactivity measurement. Samples were weighed and significantly lower than the concentrations in brown rice (P packed in either a 2-liter Marineri container or a 100-ml U8 , 0.01) and decreased more with increased polishing ratios container (Toyoshima Seisakusyo, Tokyo, Japan). The concentrations of 134Cs and 137Cs were measured by gamma-ray spectrometry in both K1 and K2 (Fig. 1A). The concentrations of using a germanium semiconductor detector (Canberra, Meriden, radioactive Cs in 100% polished rice for K1 and K2 were CT). The gamma-ray peaks in the measurements were 604.7 keV for 40 ¡ 0.1 and 69 ¡ 0.8 Bq/kg, respectively. On the other 134Cs and 661.6 keV for 137Cs. The counting times were 3,600 to hand, the concentrations of radioactive Cs in the outer layers 72,000 s, because counting errors for the measurements of 134Cs and were significantly higher than those in brown rice for both K1 137Cs were less than 10%. The radioactive Cs concentration used in and K2 in each polishing ratio type (P , 0.01), and there 134 137 this study was the sum of the Cs and Cs concentrations. Pf were no significant differences with increasing polishing indicates the ratio of the radioactive Cs concentration (becquerels ratios in either K1 or K2 (P . 0.05) (Fig. 1B). The Pf values per kilogram [Bq/kg] [fresh weight]) in processed foods to that in of polished rice for K1 and K2 were 0.48 to 0.81 and 0.47 to unprocessed foods and was calculated using the following equation: 0.81, respectively (Table 1). The rice showed significant Pf ~ A/B, where A is the radioactive Cs concentration after decreases in Pf values when the polishing ratio was increased processing (Bq/kg [fresh wt]) and B is the radioactive Cs concentration before processing (Bq/kg [fresh wt]). Fr indicates in both K1 and K2 (P , 0.01). For the outer layers, the Pf the ratio of radioactive Cs content (Bq) in processed foods to that in values of K1 and K2 were 7.1 to 7.8 and 6.5 to 7.0, unprocessed foods and was calculated using the following equation: respectively (Table 1). There were no significant differences Fr ~ C/D, where C is the radioactive Cs content after processing in the Pf values for the outer layers with increased polishing (Bq) and D is the radioactive Cs content before processing (Bq). The ratios (P . 0.05). J. Food Prot., Vol. 78, No. 3 DISTRIBUTION OF RADIOACTIVE CESIUM DURING PROCESSING OF RICE 563

germ does not break during rice polishing, unlike the parts of the bran, and hence, it could be separated from the bran by sieving. The concentrations of radioactive Cs in the germ were significantly lower than the concentrations in bran in both K1 and K2 (P , 0.01) (Table 2). The Fr values for the germ in K1 and K2 were 0.074 and 0.14, respectively.

Concentrations of radioactive Cs in wash water and cooked rice during rice cooking. Cooked rice was prepared using 100% polished rice in this study. Polished rice was washed with water to remove dust and residual bran on the surface before cooking. The polished rice was washed five times, and each time the wash water was recovered and the concentration of radioactive Cs in it Downloaded from http://meridian.allenpress.com/jfp/article-pdf/78/3/561/1683662/0362-028x_jfp-14-275.pdf by guest on 26 September 2021 was determined. The initial wash water contained the highest concentration of radioactive Cs; a gradual reduction was observed with each wash, and a nonsignificant amount of radioactive Cs was found in the water from the third wash (P , 0.05) (Fig. 3). The washed rice was cooked with 1 1/2 volumes of water using a rice cooker. The rice cooker automatically executed the soaking, heating, and holding sequences in the cooking program. Cooked rice of samples K1 and K2 contained 11 ¡ 0.1 and 20 ¡ 0.9 Bq/kg of radioactive Cs, respectively. The radioactive Cs concentrations in the cooked rice were significantly lower than those in polished rice for both K1 and K2 (P , 0.01) (Table 3). The Pf value for cooked rice was 0.28 in both K1 and K2.

Distribution of radioactive Cs in wash water and cooked rice. The amounts of radioactive Cs transferred to the wash water in K1 and K2 were 36 and 34%, respectively (Table 4). Cooked rice contained 66 and 65% radioactive Cs in K1 and K2, respectively. The recovery of radioactive FIGURE 1. Changes in radioactive cesium concentrations in Cs during cooking in K1 and K2 was 101 and 99%, polished rice (A) and outer layers (B) during rice polishing. Two respectively. samples of brown rice, K1 and K2, with different concentrations of radioactive cesium were used for polishing. Open circles and solid DISCUSSION squares indicate results for K1 and K2, respectively. Polishing. Rice polishing resulted in reduced radioactive Cs concentrations in polished rice and higher Distribution of radioactive Cs in polished rice and concentrations in the outer layers compared with the outer layers. The amounts of radioactive Cs and the Fr concentrations in brown rice. (Fig. 1). This finding values in polished rice and outer layers were investigated. In indicated that the localization of radioactive Cs in brown both K1 and K2, the Fr values for polished rice decreased rice is not uniform and that radioactive Cs presents at higher with increased mass ratios of polished rice from brown rice, concentrations in the outer layers. Previous studies have and the Fr values for the outer layers increased conversely reported that rice bran has 10-fold (19) or 16-fold (18) (Fig. 2A and 2B). The Fr value for 100% polished rice in higher concentrations of radioactive Cs than polished rice. both K1 and K2 was 0.43, and the Fr values for the outer The levels of radioactive Cs in the outer layers were 14.8- layers of K1 and K2 were 0.60 and 0.58, respectively. The fold (K1) and 13.6-fold (K2) higher than the levels in

TABLE 1. Processing factors for radioactive cesium during rice polishinga

Pf for K1 at polishing ratio (%) of: Pf for K2 at polishing ratio (%) of:

Part of rice 30 50 70 100 30 50 70 100

Polished rice 0.81 A 0.68 B 0.61 C 0.48 D 0.81 A 0.72 B 0.55 C 0.47 D Outer layers 7.2 AB 7.5 AB 7.8 A 7.1 B 6.6 AB 7.0 A 6.9 AB 6.5 B a Polishing ratios indicate the removal rate of bran. Processing factors (Pf) are calculated by dividing the concentration of Cs in polished rice or outer layers (Bq/kg [fresh wt]) by the concentration in brown rice (Bq/kg [fresh wt]) (n ~3). Different letters following values for the same part of the rice indicate significant differences between samples (P , 0.05) by Tukey’s test. 564 HACHINOHE ET AL. J. Food Prot., Vol. 78, No. 3 Downloaded from http://meridian.allenpress.com/jfp/article-pdf/78/3/561/1683662/0362-028x_jfp-14-275.pdf by guest on 26 September 2021

FIGURE 3. Concentrations of radioactive cesium in wash water of polished rice of samples K1 (A) and K2 (B). Error bars show ~ FIGURE 2. Changes in food processing retention factors for standard deviations (n 3). Different letters show significantly , radioactive cesium during rice polishing in K1 (A) and K2 (B). different values (P 0.05) by Tukey’s test. Food processing retention factors are calculated by dividing the radioactive cesium content (Bq) in polished rice or outer layers by polished rice in this study, which is comparable to the the radioactive cesium content (Bq) in brown rice. Error bars show results of previous studies. These data suggest that the standard deviations (n ~ 3). Results for polished rice are significant decreases in the radioactive Cs concentrations in indicated by solid circles or solid squares, and results for outer polished rice depend on the polishing ratio and are due to layers are indicated by open circles or open squares. the difference in radioactive Cs concentrations between polished rice and bran. All the Pf values for polished rice

TABLE 2. Concentrations and localization of radioactive cesium in germ and bran Radioactive Cs concn Radioactive Cs Sample Part Mass (kg) (mean Bq/kg ¡ SE [fresh wt])a content (Bq)b Frc Recovery (%)d

K1 Outer layers 0.34 590 ¡ 11 100 Germ 0.033 471 ¡ 12* 7.4 0.074 86 Bran 0.23 692 ¡ 13* 78 0.78 K2 Outer layers 0.35 935 ¡ 22 167 Germ 0.053 855 ¡ 8.3* 22 0.14 98 Bran 0.27 1050 ¡ 12* 141 0.85 a Arithmetic mean values ¡ standard errors were calculated from individual results (n ~3). Asterisks indicate significant differences (* P , 0.01) between values for germ and bran by t test. b Calculated by multiplying the mass (kg) by the radioactive cesium concentration (Bq/kg). c Calculated by dividing the radioactive cesium content (Bq) in germ or bran by the radioactive cesium content (Bq) in the outer layers. d Calculated by dividing the sum of the radioactive cesium contents (Bq) in germ and bran by the radioactive cesium content (Bq) in outer layers and multiplying by 100. J. Food Prot., Vol. 78, No. 3 DISTRIBUTION OF RADIOACTIVE CESIUM DURING PROCESSING OF RICE 565

TABLE 3. Concentrations of radioactive cesium and processing factors for cooked rice Radioactive cesium concn (mean Bq/kg ¡ Sample Treatment Mass (kg) SE [fresh wt])a Pfb Moisture (%)c

K1 Polished rice 0.8 40 ¡ 0.1* Cooked rice 1.9 11 ¡ 0.1* 0.28 63.2 K2 Polished rice 0.8 69 ¡ 1* Cooked rice 1.8 20 ¡ 1* 0.28 62.8 a Arithmetic mean values ¡ standard errors were calculated from individual results (n ~3). Asterisks show significant differences (* P , 0.01) between values for polished and cooked rice by t test. b Processing factors were calculated by dividing the concentration of Cs in cooked rice (Bq/kg [fresh wt]) by the concentration in polished rice (Bq/kg [fresh wt]). c Percentages of water were calculated from the mass and moisture of polished rice and the mass of cooked rice. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/78/3/561/1683662/0362-028x_jfp-14-275.pdf by guest on 26 September 2021 were less than 1, and 100% polished rice of samples K1 and 12.6-fold (K2) higher than those in polished rice; however, K2 showed Pf values of 0.47 and 0.48, respectively the concentration of Cs in the germ was significantly lower (Table 1). From these data, the concentration of radioactive than that in bran in this study. The Fr values for the germ Cs in the edible portion is estimated to be half of that in were 0.074 to 0.14 (Table 2), and therefore, the Fr values brown rice. In contrast, the Pf value for the outer layers was for Haigamai are estimated to be 0.50 to 0.57. 6.5 to 7.8 (Table 1). The Pf value of wheat bran is also known to be higher than those of wheat or flour; the Pf Cooking. Rice is commonly eaten as 100% polished value for wheat bran during milling has been reported to be rice in Japan, so we investigated the Pf and Fr values during .2 (10). Rice bran and wheat bran are used as fertilizer or cooking for 100% polished rice. Polished rice was rinsed in feed for livestock, and therefore, the Ministry of Agricul- water five times and then cooked with water using a rice ture, Forestry and Fisheries have issued a notification that Pf cooker. Transfer of radioactive Cs from polished rice to the values of 8 for rice bran and 3 for wheat bran should be wash water was observed during rice washing. The water applied (12). The Fr values for polished rice in both K1 and from the first wash showed the highest concentration of K2 decreased depending on the increased polishing ratio, radioactive Cs among the wash waters (Fig. 3), which might but for the outer layers, the Fr values increased (Fig. 2). The be due to contamination with dust and residual bran. Fr value for 100% polished rice in both K1 and K2 was Radioactive Cs was also detected in the water from the fifth 0.43. Fr values for 100% polished rice of 0.43 to 0.46 have wash, though there was no significant difference among the been reported (18), which is in remarkable agreement with wash waters after the third washing. In the case of noodle the results of this study. Thus, the Pf and Fr values for boiling, we also reported that more than 80% of the polished rice are considered to be independent of the radioactive Cs (Bq) contained in the noodles was transferred radioactive Cs concentration of brown rice. The distribution to the boiling water (7). Thus, the radioactive Cs in rice and of radioactive Cs in polished rice and the outer layers was wheat is considered to be largely water soluble. estimated to be approximately 40 and 60%, respectively. Cooked rice showed significantly lower radioactivity Rice germ is rich in proteins, lipids, vitamins, and minerals than polished rice, and the Pf value for cooked rice of both (5), so 100% polished rice with germ that is called K1 and K2 was 0.28 (Table 3). However, the recovery of ‘‘Haigamai’’ is sold in Japanese supermarkets. The radioactive Cs during cooking in samples K1 and K2 was concentrations of radioactive Cs in the germ have been 101 and 99%, respectively (Table 4), which displays no speculated to be 10- to 20-fold higher than the concentra- reduction of radioactive Cs by vaporization during cooking. tions in polished rice (17), and moreover, the germ has been These data suggest that the changes in radioactive Cs reported to show higher radioactivity than bran (18). The concentrations and Pf values for cooked rice are only due to levels of radioactive Cs in the germ were 11.9-fold (K1) and dilution of radioactive Cs by water absorption. The Pf

TABLE 4. Food processing retention factors of radioactive cesium during rice cooking Radioactive cesium content (Bq)a Fr b

Sample Polished rice Cooked rice Wash water Cooked rice Wash water Recovery (%)c

K1 32 21 11 0.66 0.36 101 K2 55 36 19 0.65 0.34 99 a Calculated by multiplying the mass (kg) by the radioactive cesium concentration (Bq/kg [fresh wt]). b Calculated by dividing the radioactive cesium content (Bq) in cooked rice or wash water by the radioactive cesium content (Bq) in polished rice. c Calculated by dividing the sum of the radioactive cesium contents (Bq) in cooked rice and wash water by the radioactive cesium content (Bq) in polished rice and multiplying by 100. 566 HACHINOHE ET AL. J. Food Prot., Vol. 78, No. 3 values among soybeans foods, including tofu, natto, and 5. Gopalakrishna, A. G., R. G. Raja Rajan, and A. S. Bhatnagar. 2012. nimame, were different, which involved dilution of Rice bran: chemistry, production and applications—a review. radioactive Cs by water absorption (6). Beverage Food World 39:31–36. 6. Hachinohe, M., K. Kimura, Y. Kubo, K. Tanji, S. Hamamatsu, S. Nonradioactive potassium is known to show behavior Hagiwara, D. Nei, H. Kameya, R. Nakagawa, U. Matsukura, S. similar to that of radioactive Cs in food (6, 18). The use of Todoriki, and S. Kawamoto. 2013. Distribution of radioactive cesium potassium as an indicator of radioactive Cs was suggested in (134Cs plus 137Cs) in a contaminated Japanese soybean cultivar during estimating the fate of radioactive Cs (6). The Pf values for 50, the preparation of tofu, natto, and nimame (boiled soybean). J. Food 70, and 100% polished rice and cooked rice calculated from the Prot. 76:1021–1026. 7. Hachinohe, M., S. Naito, H. Akashi, S. Todoriki, U. Matsukura, S. food composition table were 0.65, 0.52, 0.38, and 0.32, (2) Kawamoto, and S. Hamamatsu. 2014. Effect of noodle size and respectively. These values were comparable to those of boiling time on dynamics of radioactive cesium during cooking of radioactive Cs determined in this study, and this finding also Japanese udon noodles. Jpn. Soc. Food Sci. Technol. 61:34–38. (In suggests that potassium contents might be suitable for estimation Japanese.) of radioactive Cs during polishing and cooking of rice. 8. International Rice Research Institute. Rice milling. Available at: The results of the present study demonstrate that the http://www.knowledgebank.irri.org/ericeproduction/PDF_&_Docs/ Downloaded from http://meridian.allenpress.com/jfp/article-pdf/78/3/561/1683662/0362-028x_jfp-14-275.pdf by guest on 26 September 2021 Teaching_Manual_Rice_Milling.pdf. Accessed 1 April 2014. radioactive Cs in brown rice was reduced by polishing to 9. Juliano, B. O. 1993. Rice in human nutrition: grain structure, remove the outer layers. Additionally, water absorption composition and consumers criteria for quality. Food and Agriculture contributes to a decrease in the concentration of radioactive Organization of the United Nations, Rome. Cs in cooked rice, although no reduction occurred during 10. Kimura, K., H. Kameya, D. Nei, Y. Kakihara, S. Hagiwara, H. cooking. 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