¹³⁷Cs Analysis by Gamma Spectrometry and Its Potential for Dating Portuguese Old Wines

Analytical methods for dating wines often involve assessments of anthropogenic ¹⁴C, ¹³⁷Cs, and cosmogenic ¹⁴C. Having in mind the commercial and historical significance of rare and aged wines, this study focuses on noninvasive and nondestructive ¹³⁷Cs detection. The approach relies on measuring gamma-emitting radionuclides within the energy range of 46.5-1836 keV using Hyper Pure Germanium (HPGe) detectors, specifically calibrated for horizontally positioned sealed wine bottles. The ¹³⁷Cs dating method was optimized to achieve low detection limits and was validated for accuracy. All the activities were normalized to the same arbitrary date, and each sample was measured twice. For the first time, Portuguese fortified and nonfortified wines were analyzed for ¹³⁷Cs content. Wines from the 1960-1965 vintages exhibited ¹³⁷Cs levels between 0.51 Bq/L and 1.74 Bq/L, varying by wine region and type. Fortified wines consistently showed lower ¹³⁷Cs levels than nonfortified wines, likely due to differences in the production process. The method is particularly effective for distinguishing wines produced around the 1963 bomb peak and a few subsequent years, though further research is needed to expand its applicability to other periods.