Specific activities of natural radionuclides (²²⁶Ra, ²²⁸Ra and ⁴⁰K) in solid and liquid fractions of cocoa and cacao pod (Theobroma cacao L.)

Cocoa, deeply connected to the history and myths of many cultures, is a primary crop used mainly for the production of chocolate. The main cocoa varieties are Criollo, Forastero, and Trinitario, distinguished by their morphology, genetics, and geographical origin. In the present study, activity concentrations and committed effective dose due to ingestion of ⁴⁰K, ²²⁶Ra and ²²⁸Ra were measured. The present study is particularly notable for being the first in the literature to measure the specific activities of these radionuclides by separately analyzing the different fractions of the cocoa pod (such as the pod shell or exo carp, endocarp, placenta and funiculi, beans, and pulp). This individualized approach provides a deeper understanding of radionuclides presence in the various parts of the cocoa bud. Consumption data and dose coefficients were obtained by the Instituto Brasileiro de Geografia e Estatística and data published by ICRP 119. The samples were tested by gamma spectrometry using high purity germanium (HPGE). Detection efficiency for each sample was obtained using LabSOCS software. For cocoa beans, the main contributor to the specific dose results were ²²⁶Ra and ²²⁸Ra activities. This is because these radionuclides have the highest conversion factors for effective dose. On average, ²²⁸Ra contributes 8.56 µSv⋅year^-1 and ²²⁶Ra 5.19 µSv⋅year^-1. The results in this study align with those of other authors in terms of order of magnitude when using the same methodology for samples of different foods. For element ⁴⁰K, the study shows that a higher concentration of activity was found in the endocarp of the cocoa pod, reaching a value of 1350.19 ± 64.63 Bq⋅kg-1. The placenta and funiculi of the cocoa pod had the second-highest concentration, with 961.03 ± 64.33 Bq⋅kg-1. Finally, the cocoa bean shell showed the third-highest concentration of activity, with 782.09 ± 45.07 Bq⋅kg^-1. In the case of cocoa bean samples, the mean activity concentration was 211.06 ± 16.97 Bq⋅kg^-1. As for element ²²⁶Ra, the highest concentration of activity was observed in the placenta and funiculi of the cocoa pod, with a concentration of 21.03 ± 40.29 Bq⋅kg^-1. The lowest concentration of activity was found in the endocarp, with 2.91 ± 3.82 Bq⋅kg^-1. As for the element ²²⁸Ra, the highest concentration of activity was also recorded in the placenta and funiculi of the cocoa pod, with 12.15 ± 15.01 Bq⋅kg^-1. The lowest concentration of activity occurred in cocoa beans, with an average of 4.56 ± 3.35 Bq⋅kg^-1. It was not possible to quantify the activity levels in the pulp. The three samples tested showed activity levels below detection limits for radionuclides ²²⁶Ra, ²²⁸Ra and ⁴⁰K. (author)