🍷 Barrel toasting

Barrel toasting (toast, barrel charring) is heating an oak barrel from the inside over a fire once it has been assembled. The heat helps bend the boards and, at the same time, changes the wood itself. Furanic compounds, vanillin and oak lactones appear, and with them the smells and flavours that later pass into the wine.

Toast comes light, medium or heavy. The heavier it is, the smokier the taste, though some wood compounds break down. In the studies, wines from lightly toasted barrels tasted less sweet and less bitter but more astringent. On medium toast, oak chips gave more woody, vegetal and smoky notes, along with bitterness and astringency.

The cooper chooses the degree, and each one does it differently. Cognac coopers toast to varying degrees and for varying times to make different aroma profiles. One American cooperage runs a medium-light toast of about 40 minutes over fire pits, which crystallises the sugars in the wood. A Kentucky cooperage heats from several minutes to over an hour and then chars with open flame, graded from 1 to 4.

Toasting and oak ageing are two separate steps. The cooper does the first and gives the wood its flavour. The winemaker does the second and decides how long that wood hands its flavour to the wine. The hoop holds the barrel's shape, and the bung closes it once the wine is inside.