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. 23 Both techniques require further validation with larger and more diverse data sets to confirm their generalizability across different wine types and regions. On the other hand, isotopic detection and measurement are based on objective, quantifiable data, reducing the potential for interpretation errors. Several isotopes have been used for dating wine samples. Among them, anthropogenic tritium (T or 3 H), carbon-14 ( 14 C), cesium-137 ( 137 Cs), and cosmogenic carbon-14 ( 14 C) assessments play important roles. 24 − 30 The tritium technique has some limitations due to more recent fallouts from nuclear reactors. 31 The methodologies for determining the radiocarbon ( 14 C) age of ethanol and sugar residues can be unreliable in cases of sugar addition to the product 32 and usually involve tedious preparation of a sample, most of the time from distillation. 30 Although 14 C dating is always destructive, a fact that is limiting its use when high-priced wine bottles are under investigation, 137 Cs dating can be used in invasive or noninvasive mode. Several characteristics of 137 Cs make it an ideal nondestructive marker for dating analytical techniques. Cesium exists in nature entirely as 133 Cs, which is stable and However, their special vinification process, including spirit addition (in a proportion ∼20% of the final volume) and extensive aging periods, 39 could distinguish them in terms of radionuclide composition in comparison with nonfortified wines. First of all, keeping in mind that the studies involving the dating of wines by radionuclide quantification have been focusing on table wines, a comparison study of both styles could reveal the effect of the vinification process on 137 Cs levels in wine samples. In contrast, the Type 2 bottle measured 295 mm in height, and maintained the same 75 mm diameter but exhibited a light green color. The tests were conducted in duplicates, and the recovery (%) was calculated to evaluate the method’s performance. Moreover, to investigate the attenuation of the signal arriving to the detector and its relationship with sample geometry, a radioactive source of 137 Cs was positioned at the top of 3 different wine samples with no 137 Cs activity (bottles 1, 2, 3), and the top of a bottled spiked model wine (bottle 4). Pico wine samples and samples from the Península de Setúbal wine region were not included in the reference curve construction due to the limited number of samples available and their unique geographical conditions. The influence of ocean currents and other environmental factors in these regions is nonhomogeneous, making it difficult to establish a consistent reference curve for comparison. Figure 3 Reference curve for Porto fortified wine samples. Figure 4 Reference curve for Dão nonfortified wine samples. The reference calibration curve constructed from Porto wine samples revealed no detectable activity of 137 Cs before 1960 and after 1965. While no activity study of 137 Cs has ever been conducted in Porto wine to the best of our knowledge, other studies considering special wines like botrytized wines (Tokaj) are reporting as well high activity of 137 Cs from the years 1963 (1.01 Βq/L) and 1964 (0.87 Βq/L). 54 In the same study, 137 Cs was detectable in Tokaj wines from 1958 until 1965. These differences can be attributed to the different methodologies used for the quantification of 137 Cs, vinification, and aging processes of these wines, and the different geographical locations of the wine-producing regions. 7 , 27 , 58 Radionuclide behavior seems to be influenced by plant physiology, with stalk and skin/seeds tending to accumulate more 137 Cs than juice or pulp. 59 Comparing the two distinct reference curves for fortified and nonfortified wines, it is obvious that the activity range 137 Cs is more limited for fortified wines, exhibiting the lowest activity of all the samples under study (highly significant difference p < 0.001). This could be attributed to the different geographical and topological characteristics of the wine region and the unique nature of Porto wine. Since 137 Cs is more soluble in water than in ethanol, the reduced water content could result in lower overall cesium retention in Porto wine compared to wines obtained by complete fermentation of the must (nonfortified wines), which has a higher water content and lower ethanol. 60 Higher alcoholic strength by volume could facilitate the precipitation or complexation of 137 Cs with other elements 61 or compounds present in wine. 61 Competing ions, particularly potassium (K+) and stable cesium isotope 133 Cs have been shown to influence 137 Cs behavior.