Vanilla is a flavoring agent derived from the fruit of the orchid Vanilla planifolia, which is native to Mexico, but is now cultivated in tropical regions around the world. It is the second most expensive spice in the world, after saffron. The vanilla fruit are commonly called beans, because they resemble bean pods, each about 15 to 30 cm (6 to 12 inches) in length. Each fruit is harvested when ripe and then goes through a lengthy curing process, which can take up to 2 years, although 6 months is more common.
Vanilla is most widely available as an alcohol-based liquid extract; vanilla flavor and aroma are extracted from ground pods through maceration in ethanol. Natural vanilla extract is a combination of hundreds of chemical compounds making for a very complex aroma and flavor, but the dominant chemical component is vanillin. Because natural vanilla is so expensive, the vast majority of vanilla flavor used today is actually artificial vanillin, which is derived very inexpensively from lignin, a wood by-product of the paper industry.
When used as a flavoring agent in beer, vanilla is most often found in winter seasonal beers, where the sweet aroma pairs nicely with other festive spices like cinnamon, allspice, and clove. Vanilla can be added at any of several stages in the brewing process. Most commonly, vanilla beans or liquid vanilla extract is added either at the end of the boil during the whirlpool stage before wort is transferred for fermentation or postfermentation before packaging. Whole beans can be used to “dry spice” the beer in the fermenter in a technique similar to dry hopping. Whole vanilla beans can also be added to a firkin or a pin to flavor a beer during cask conditioning.