If you have drank enough whiskey to notice the all the unique flavors, you might wonder why does most aged bourbon taste so much like vanilla?
It all starts with White American Oak barrels and the char that each distillery uses to make their distinct bourbon taste. For bourbon to be legally called bourbon, it needs to be aged in new charred oak barrels for at least 3 years. The wood, American white oak has a large amount of wood sugar within the wood. When the bourbon barrel is charred on the inside it creates a few organic compounds and one of these flavor enhancing compounds is called vanillin.
“Vanillin”, C8H8O3, is found in nature not only in wood but also in vanilla beans, maple syrup, banans and even butter. The highest concentration of vanillin found in nature is in vanilla beans where 2% of their body weight is the organic compound vanillin. You will notice that vanilla extract consists of a large percentage of alcohol in the extract. The reason for this is that vanillin has a high solubility in alcohol. While bourbon is sitting in barrels (at least 3 years legally) it has a long time to dissolve all the available charred vanillin in the wood. By charring the bourbon barrels at different degrees of char it will create a different tasting vanillin compound ranging from a light flowery vanilla to a deep toffee flavor. Other spirits can contain some amounts of vanillin and if you can taste a flavor of vanilla in the flavor profile there is a good chance there is vanillin in the spirit.