The oak barrel has long been prized for its aging powers on wine and whiskey. Now barrel-aging has become trendy in beer-making, too, with craft beer makers from California to Europe giving their brews a taste of oak.

The trend has taken on a sour-ale flourish with West Coast producers like Russian River and Port Brewing - a Belgian-style genre of its own worth exploring in a future column. Locally, whiskey barrels have been well used on more familiar styles by Stoudt's in Adamstown, which softens the edges on some of their brawniest, darkest, cork-topped beers like Fat Dog Stout and Old Abominable Barley Wine.

Few beers, though, so vividly show the caramelizing influence of oak as this malty Scottish ale from Innis & Gunn. Made initially simply to flavor the casks used for an "ale-finished" Scotch, this by-product brew turned out to be special, too, with a distinctly vanilla toffee edge balanced by just enough of a fruity finish to keep it from cloying.

A 750ml bottle of Innis & Gunn is $15 at two Fairmont restaurants (London Grill, Brigid's), and $12.40 at the Latimer Deli, 255 S. 15th St., 215-545-9244.

- Craig LaBan