How Burning Transforms Wood into Flavor

Burning temperatures transform each of the wood components into a characteristic group of compounds (see box). The sugars in cellulose and hemicellulose break apart into many of the same molecules found in caramel, with sweet, fruity, flowery, bready aromas. And the interlocked phenolic rings of lignin break apart from each other into a host of smaller, volatile phenolics and other fragments, which have the specific aromas of vanilla and clove as well as a generic spiciness, sweetness, and pungency. Cooks get these volatiles into solid foods, usually meats and fish, by exposing the foods to the smoky vapors emitted by burning wood. Makers of wine and spirits store them in wood barrels whose interiors have been charred; the volatiles are trapped in and just below the barrels’ inner surface, and are slowly extracted by the liquid.