Use of gamma spectroscopy for characterization and traceability of beans

The ϒ-ray spectroscopy is the quantitative study of the ϒ spectra of and finds applications in a very large number of fields, from the astrophysics to the geochemistry. The radionuclides are instable isotopes because of an excess of nuclear energy that must be released, leading to the formation of more stable nuclides. One of the possible releasing mechanisms is the emission of gamma radiation. A spectrum is characteristic, in terms of energies and intensities, of the nuclides present and allows to determine their quantity and the nature of sample under investigation. This offers the possibility of obtaining specific information, which can be acquired only with difficulty or even not at all by other techniques.

This is also true in the field of food characterization and their traceability.

The traceability in the food industry has become a fundamental request for the modern society. It consists in the ability of tracing any food, feed or substance used for consumption, through all stages of production, processing and distribution. For this reason, it is essential to provide transparency and safety to consumers who are demanding high quality products, with good nutritional characteristics. In the same moment, it is also important for producers, because it ensures certification and accreditation of their products. Traceability is indeed a way for ensuring that all food products are safe.

In order to achieve this goal, it is necessary to use specific experimental techniques, sometime developing innovative solutions. In this paper, an application of the ϒ spectroscopy to the food traceability is presented.

The gamma-emitting radionuclides can be used as markers for establishing correlations between soil and plants. Actually, a plant cannot have a much different amount of radioisotopes and a different isotopic composition than the soil in which it grows. This can make possible to trace a product and ascertain the place where it was produced.

A study of the γ characterization of some Italian bean (Phaseolus vulgaris) varieties with different geographic origins, using a portable AMETEK ORTEC High Purity Germanium (HPGe) Radiation Detector, is presented.

Beans are suitable for this study because they are rich in potassium, which exists in nature with a relatively high abundance of its radioactive isotope ⁴⁰K. Its content in different parts of the plant, such as seeds, pods, leaves, has been measured, along with the presence of other radioisotopes. This has also allowed us to establish correlations between this element and macro elements, such as carbon and nitrogen, measured by elementary combustion.

It was possible to verify the relationship between the concentration in the seeds and in the soil. Attention was also paid to the content of other radioisotopes, especially those of alkaline metals such as cesium. Due to their chemical nature, they can mimic the biological behavior of potassium and be absorbed. This may suggest further use of the cultivation of beans or leguminous plants as a possible method of bioremediation for polluted soils, because they can accumulate some specific contaminants. In principle it is also possible to recognize radioactivity arising from natural and anthropogenic origin in  the soil.