What is Happening in the Barrel: Part 1

Lignin: The Molecule

     Dr. Don Livermore of Wiser's/Hiram Walker, spoke on "the most underappreciated molecule", lignin.  Lignin is a complex organic compound that binds to cellulose fibers that hardens and strengthens the cell walls of plants.  Lignin is a polymer consisting of various aromatic alcohols, and is the chief noncarbohydrate constituent of wood. The lignin is broken down and transformed via cooking and distillation into compounds producing the flavor notes of clove and smoke, as well as the particularly distinctive spicy note we associate spirits, from 4-ethyl guaiacol.  Following through to distillation, Livermore discussed how the yeast-derived flavors of a spirit, fruity, floral, green grass, soapy, and sulfur are separated through pot distillation: the sulfur removed by the copper of the still; the green grass notes in the head cuts of distillation; the soapy notes in the tails cut.

Where the Flavors Come From

     In maturation inside an oak barrel, that magical lignin comes up again, in a role Livermore calls the "mortar to the bricks" of cellulose and hemicellulose that make up most of the wood. When burned in the barrel charring process, the broken down lignin products add to many of the smoky, phenolic components to the aging spirit, while the cellulose and hemicellulose impart many of the caramel-type flavors.

     Livermore finished with some counter-intuitive experimental data showing that more char on a barrel doesn't necessarily lead to more wood extractives in the spirit aging inside of it. He found that a new barrel charred to two millimeters depth gives more wood extractives than one charred to a four millimeters depth.