Reduction in the Radiocesium in Meats of the Sika Deer and Wild Boar by Cooking

Reduction of Radiocesium in Internal- and Surface-Contaminated Komatsuna (Brassica rapa var. perviridis) during Washing and Processing

Radiocesium dynamics data during food processing are required for the realistic estimation of internal radiation content in food. Radiocesium contamination of leafy vegetables can occur externally due to the adhesion of fallout and/or resuspension from the air, and internally from soil via the root transport. Information regarding the dynamics of both surface and internal radiocesium contamination during food processing is required; however, such information for leafy vegetables is limited compared to other major agricultural products. In this study, the effect of washing on the removal of surface radiocesium contamination by resuspended materials and that of cooking (grilling, boiling, and microwave heating) on internal radiocesium contamination were investigated using komatsuna (Brassica rapa var. perviridis), a leafy vegetable. The surface-contaminated samples were experimentally grown in a difficult-to-return area in Fukushima Prefecture, which has not yet been decontaminated. The internally contaminated komatsuna were obtained after experimental cultivation in a greenhouse with soil containing ¹³⁷Cs and no surface contamination. The concentration of ¹³⁷Cs in surface-contaminated komatsuna was reduced to approximately half (processing factor: 0.55) after washing with water. However, the annual processing factor ranged from 0.12 to 0.95, suggesting that the growing environment and climatic conditions may affect the removal rate of radiocesium by washing. Internal contamination of ¹³⁷Cs was removed by 23% and 14% by boiling and grilling, respectively, but no effect was observed for microwaving. Moreover, the concentration of ¹³⁷Cs decreased by 0.66-fold after boiling, while it increased by 1.19- and 1.20-fold after grilling and microwaving, respectively. Therefore, boiling was found to be preferable than grilling or microwaving for radiocesium removal.

Distribution of Radioactive Cesium during Wild Boar Meat Processing

ABSTRACT

Wild boar meat containing radioactive cesium (Cs) of approximately 1,000 Bq/kg (134Cs+137Cs) was processed into bacon, sausage, and ham. To understand the concentration and quantity change of radioactive Cs, the processing factor (Pf) and food processing retention factor (Fr) were calculated. The radioactive Cs quantity in the meat did not reduce during smoking. The dehydration-related meat mass reduction during smoking without decrease of radioactive Cs led to Cs condensation in the bacon compared with the raw rib meat before processing, resulting in a Pf of 1.18. Soaking in liquid, such as pickling in liquid and desalting or boiling in water, effectively removed radioactive Cs by leakage into water. Therefore, the Fr value of the boiled ham produced from a loin meat block through three liquid-soaking processes was 0.27. The Pf value of the boiled ham was 0.30 due to meat block mass reduction after boiling as a result of dehydration, along with protein thermal denaturation-related muscle tissue shrinkage. The steamed ham Fr value was 0.53, because the removal of radioactive Cs was less efficient by steaming than by boiling. The Pf value of the steamed ham was 0.54, almost the same as the Fr value, because the mass decrease rate was the same as the radioactive Cs decrease rate by steaming. The Fr and the Pf values of the boiled sausage, whose processing did not include soaking in the pickling liquid, were 0.64 and 0.62, respectively. Steaming the sausage meat did not remove radioactive Cs during the dehydration-related mass reduction, leading to Fr and Pf values of 1.01 and 1.17, respectively. This study found that processing into boiled ham was the most effective measure for reducing radioactive Cs quantity and concentration in raw meat. Processing into bacon and steamed sausage showed no Cs quantity reduction, with the moisture loss resulting in Cs condensation compared with the raw material.

HIGHLIGHTS

Radioactivity in Calabrian (Southern Italy) Wild Boar Meat

The production chain for game meat is specific and differs from the production chain of meat from domestic livestock. Wild boar meat is a foodstuff consumed in Italy. Wild boars are considered as a reservoir of environmental radionuclides, and the accumulation of radioisotopes can pose a radiological hazard. 40K and 137Cs activity concentrations were measured through HPGe gamma spectrometry in wild boar meat samples, coming from six hygiene points representative of the entire district of Reggio Calabria, South Italy. Experimental values were found to be in the range of (91 ± 11) Bq kg−1 to (117 ± 14) Bq kg−1 for 40K and of (0.09 ± 0.03) Bq kg−1 to (1.61 ± 0.24) Bq kg−1 for 137Cs, respectively. Any possible radiological risk for the population was also estimated. Obtained values are in the range of 2.66 µSv a−1 to 4.00 µSv a−1, much lower than the recommended level for the public (1 mSv a−1).