Final answer:
To verify a wine's vintage, oenologists may analyze the cesium-137 activity in the wine, as the presence of this radioactive isotope in significant amounts before 1950 is an indicator of a forgery. The EU labeling laws would typically require that a majority of the wine be from the indicated vintage year.
Step-by-step explanation:
The EU labeling laws stipulate that if a wine label indicates a vintage date, a specific percentage of the wine must indeed be from that year. Although the exact figure is not provided in your question, it is common in many regions for the requirement to be that at least 85% to 95% of the wine must be from the specified vintage year. To verify the authenticity of a wine's vintage, oenologists (wine scientists) can analyze the wine's cesium-137 activity. This is because cesium-137 is a radioactive isotope released into the environment from nuclear tests and disasters such as Chernobyl since the mid-20th century.
Wines that claim to be from before about 1950 but show measurable cesium-137 activity are likely to be forgeries, considering that cesium-137 was not present in the environment in significant amounts before this time. The proper identification of vintage through cesium-137 levels, considering its half-life and known environmental concentration over the years, is crucial for determining the authenticity of wines, especially when it comes to high-value vintages sought after by collectors and enthusiasts.