As an expert sommelier and brewer, I can confidently say that whiskey does not necessarily spoil in a decanter. However, there are some factors to consider when storing whiskey in a decanter for an extended period of time.
Whiskey, unlike wine, does not oxidize in the same way and therefore does not turn into vinegar. The high alcohol content in whiskey acts as a preservative, preventing spoilage. However, prolonged storage in a decanter can lead to some changes in the whiskey's characteristics.
One potential issue with storing whiskey in a decanter for too long is the risk of evaporation. Whiskey is more volatile than wine, meaning it can evaporate more quickly. This can lead to a loss of volume and potentially alter the flavor profile of the whiskey over time. To minimize this risk, it is recommended to store the decanter in a cool and dark place, away from direct sunlight.
Another concern with extended storage in a decanter is the potential for flavor degradation. Whiskey can interact with the air and the glass of the decanter, which can lead to a loss of flavor intensity over time. This can result in a less vibrant and nuanced drinking experience. To preserve the flavors of the whiskey, it is advisable to consume it within a reasonable timeframe, preferably within a few months to a year of decanting.
It is worth noting that the effects of prolonged storage in a decanter can vary depending on the specific whiskey and its individual characteristics. Some whiskeys may be more resilient to these changes, while others may be more sensitive. Additionally, the quality of the decanter itself can also play a role in how the whiskey is preserved.
In my personal experience, I have found that whiskey stored in a decanter for an extended period of time (over two years) can indeed show some signs of discoloration and a loss of flavor intensity. The whiskey may appear slightly darker and the flavors may not be as vibrant as when it was first decanted. However, this does not necessarily mean that the whiskey is spoiled or undrinkable. It may still be enjoyable, albeit with some subtle changes in character.
To summarize, while whiskey does not spoil in a decanter like wine would turn into vinegar, prolonged storage can lead to some discoloration and a loss of flavor intensity. It is generally recommended to consume decanted whiskey within a reasonable timeframe to fully enjoy its original characteristics.