We have written about the different types of casks in our previous post, so now it is time to dive deeper into the wood itself to find out how it influences the final whisky produced. Two predominantly different types of wood are used for casks and both influence the liquid maturing in them differently.

The effect on taste for the 2 types of wood

Type of Wood	Effect on Taste
American White Oak	Vaniila, Caramel, Soft, Mellow
European Oak	Bitter, Spicy, Strong Woody Taste

There are huge differences between these 2 popular oak casks. The American White Oak grows in the eastern part of America and some parts of Canada. This particular oak tree grows faster than others, making it more affordable as a cask. The dense wood contains a lot of mono-galloyl glucose, which transfers into the typical Bourbon vanilla taste.

The European Oak grows all over Europe, including Russia and Turkey. Its slower growth makes it more expensive and is slightly less dense than the American counterpart. The wood contains Gallic acid. This acid is a pseudo tannin, giving rise to the slightly bitter notes in a whisky matured in European oak when water is added. The European oak also adds to the spiciness of the whisky due to other components within the wood.

The effect on taste from the types of predecessor liquid in the cask

The predecessor liquid in the whisky cask also influences in the taste of the whisky. Here’s a table of the different liquids and how they influence the taste of the whisky.

Predecessor	Type of Liquid	Influence on Taste	Influence on Colour
Amarone	wine	very fruity, lightly sweet, lightly dry	dark red
Barolo	wine	sweetness, zest, acidity, light fruits	bright to amber
Bordeaux (red)	wine	strong red fruits, grapes (wine), berries	red
Burgundy	wine	light fresh fruits (citrus, mango), very sweet,	bright to amber
Chardonnay	wine	fruits, tannins (bitter), dried fruits, heavy aromas	red
Muscat	wine	lean, crisp, acidic, tropical fruits	bright
Sauternes	wine	floral , sweet, citrus, peach	bright/red
Tokaji	wine	tannins (bitter), dry, raisins, ripe fruits	red
Madeira	fortified wine	spiciness, light fruitiness, sweetness, dryness	dark, amber
Marsala	fortified wine	sweet, dried fruit, spiciness	red
Muscat	fortified wine	lightly sweet, dried fruit, spiciness	red
Port (dry)	fortified wine	dry, dried fruit, spiciness	red
Port (semi-dry)	fortified wine	very fruity, dark fruits, berries	red
Port (sweet)	fortified wine	very sweet, dark fruits, raisins, syrup	amber
Ruby Port	fortified wine	sweet, complex, spices	dark red
Amontillado	sherry	deep, dark, nutty, dark ripe fruits	red, amber
Fino	sherry	very sweet, dark fruits, raisins, syrup	amber
Manzanilla	sherry	light fruits, sweetness, dryness, light wood	bright
Oloroso	sherry	salty, dryness, sea flavours, fresh, some fruit	bright
Palo Cortado	sherry	sweetness, nutty, dry, fresh, acid	amber
Pedro Ximenez (PX)	sherry	rich, sweet, dry, sweet spices, fruits	brown
Rum (white)	spirit	sweet, molasses, vanilla, tropical fruit, almond	bright
Rum (dark)	spirit	sweet, syrup, dark fruits, oak, caramel, vanilla	amber
Bourbon	whiskey	vanilla, sweetness, caramel, creamy	golden

The Effects of Charring and Toasting of the Casks

Charring and toasting convert the wood sugar into caramel and vanilla flavours that typically grace whiskies. Toasting means to darken the top of the wood and the depths of the staves. It is identified by a black, flat layer on top. Charring means to burn the wood to a point where the surface breaks. It has an uneven top layer and looks like an alligator skin. The time that the barrel is burned determines the level of charring.

The Effects on Reusing the Casks

Finally, the number of times that a cask is reused also affects the final whisky. A cask that is reused multiple times releases fewer flavours into the whisky. Usually, the casks are milled and charred again to restore caramel and vanilla flavours for maturation before they are refilled with whisky. The only exception is bourbon, where only fresh casks are used.

 

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