Variations in the transfer of radiocesium (137Cs) and radiostrontium (90Sr) from milk to cheese

This study aimed to compare the transfer of 2 manmade radionuclides, radiocesium (137Cs) and radiostrontium (90Sr), from cow milk to whey and cheese in 3 different types of French cheese production with rennet coagulation. Most of the 137Cs was present in the aqueous phase and became concentrated in the whey. For 137Cs transfer to whey, the processing factor (Pf; i.e., the ratio of the activity concentrations) ranged between 0.86 and 1.30 (n = 12). The food processing retention factor (Fr), calculated using the processing efficiency, ranged between 0.85 and 1.19 (n = 9). No statistical difference of Pf and Fr to whey is identified for 137Cs and the cheese products. The Pf calculated for 90Sr transfer to cheese ranged between 3.95 and 12.16, with significant differences depending on the type of cheese. In addition, a linear correlation is observed between 90Sr Pf to cheese and the Ca level in the cheese (r2 = 0.57). Thus, the Pf is enhanced in hard cheeses that are enriched in calcium. This is confirmed by nearly constant Fr values, ranging between 0.66 and 0.83.