Oak adjuncts & barrel production/chemistry

In terms of tannin (mouthfeel and anti oxidants) and oak lactones (coconut and celery) what does French oak offer?

French oak has approximately 10% tannin by weight

French oak has cis-lactone (coconut) to trans-lactone (celery) ratio of 2:1

In terms of tannin (mouthfeel and anti oxidants) and oak lactones (coconut and celery) what does American oak offer?

American oak has a maximum of 2% tannin by weight

American oak has a cis-lactone (coconut) to trans-lactone (celery) ratio of 10:1

What factors are important during the seasoning of oak adjuncts?

Sun - creates heat and reduces the woods moisture content for coopering

rain - creates a moist environment for fungi and also leaches tannin

fungi - changes oak’s composition

frost/ice - the action of freeze/thaw breaks down the oaks structure

wind - circulates air through the stave stacks

which in combination make the wood polymers break into smaller molecules

What does oak hemicellulose break into during seasoning?

Starts to break into simple sugars like: Xylose and rhamnose

Describe the chemical changes that occur during oak toasting

• Low temperatures (100–150 °C): Breakdown of hemicellulose begins, releasing simple sugars and sweet, coconut-like aromas (e.g., furfural, 5-methylfurfural).

• Moderate temperatures (150–200 °C): Increased caramelisation of sugars and lignin degradation starts, forming vanillin and spicy/clove-like compounds (e.g., eugenol).

• High temperatures (200–250 °C): More intense lignin breakdown, forming smoky, toasty, and charred aromas(e.g., guaiacol, 4-methylguaiacol). Tannin structure also starts to degrade.

• Very high temperatures (>250 °C): Formation of burnt, bitter, and smoky compounds, potentially reducing desirable aromas if overdone.

What different formats does oak come in?

Chips, cubes, powder, staves

In terms of the different adjuncts, chips, cubes and tank staves, describe their extraction capacity and flavour extraction

Chips - fastest extraction, singular flavour

cubes - fast extraction, more complex flavour than chips

tank staves - slower integration, complex flavours

What does a heavy toast compared to a light toast give you?

heavy toast - aromatics

light toast - structure