Last time we looked at the differences between new oak versus neutral oak wine barrels. New oak imparts lots of flavors to wine. But after about three vintages, the oak no longer imparts flavor so it is called neutral oak.
Much of the flavor imparted by the oak occurs naturally from the raw wood. But winemakers learned long ago that by "toasting" the inside of an oak barrel, they can enhance these flavors.
After a barrel is built, its inside can be exposed to fire to "toast" it. This is done either over an open flame or using a hand-held torch. The fire 'caramelizes' the wood's natural sugars and brings out complex compounds. From this, the wine will ultimately take on flavors that are toasty, charred, spicy and sweet depending on the amount of time the wood is toasted.
A lightly toasted barrel spends about 25 minutes exposed to flame while a heavily toasted barrel may get up to one hour of flame exposure.
Essentially, the heavier the toast, the stronger and more varied are the imparted flavors:
Light Toasting - Vanilla, coconut, caramel, clove and cinnamon
Medium Toasting - Vanilla, honey, caramel, toast, coffee, cocoa
Heavy Toasting - Vanilla, espresso, smoke, crème brûlée, butterscotch, toffee, molasses
Oak interacts with wine differently depending of the different grape varieties. Oak may impart hints of chocolate to a Merlot, and vanilla or coconut to a Zinfandel. White wines aged in oak (think Chardonnay) typically develop flavors of vanilla, baked apple, caramel, honey, toasted marshmallow, or buttered toast.
A winemaker will decide on what degree of toasting is appropriate for their wine’s style. Our 'job' is to enjoy all the wonderful flavors that oak, and toasted oak, add to our wine. Cheers!