Every type of cask has something in common, contributing vanilla notes being a prime example, but each also has something individual to offer malt whisky. Port casks for instance dispense strawberries, raspberries, blackberries, sloes and damsons, accompanied by distinct richness. But the influence goes beyond the boundaries of flavour.
“Port casks lift and lengthen malt whisky, making it more expansive and richer. If a fruity, malty style can be said to sit in the middle of a piano, a Port cask also takes this up an octave with elegance and finesse that includes minty notes with damson and dark fruit. Port casks also take a malt down an octave into bitter-sweet, like dark chocolate which has a fruitiness,” says Rachel Barrie, master blender, BenRiach Co, which includes GlenDronach, BenRiach and Glenglassaugh.
Such an impact requires master blenders to play the role of matchmaker.
“You must ensure the character of your malt is compatible with the influence of a Port cask. Dalmore, for example, has the body and character to be a perfect fit.
“I’m looking for Port to display its beautiful red fruit notes, and add a velvet texture,” says Richard Paterson, Whyte & Mackay’s master blender.
Casks are typically ex-ageing stock sold by Port houses to cooperages, which in turn supply distilleries in Scotland. Direct relationships between distilleries and Port houses exist, but are rarer.
“For The Dalmore I have an exclusive contract with Graham’s Port, stipulating an annual number of Port casks, though we’re also looking for any additional casks that Graham’s Port can supply,” adds Richard.
Port casks are coopered from American or European oak (the latter being more traditional). Both options contribute similar flavours, including vanilla, though the influence of American oak is usually less intense than European oak, which has higher tannin levels.
The interiors are toasted (but not ignited or charred) using a flame, with the heat breaking down some of the oak’s structural components.
This in turn ‘activates’ flavour compounds such as vanillin (which gives vanilla notes) within the toasted layer of oak.
Cooperages offer varying levels of toasting, from ‘light’ to ‘heavy plus,’ typically resulting in a two to three millimetre toasted layer.
“Differences between European oak and American oak Port casks are minimal, and a light toast is usual as any more can give a carpenter’s shed influence and promote heavy spice notes,” says Richard.
Port casks, known as pipes, have a capacity of around 600-650 litres, and a distinctive cigar shape.
Downsizing also happens, resulting in hogsheads (250l) and other smaller sizes such as 100 litres. “Smaller sized Port casks have a more immediate impact, giving greater sweetness and fruit richness, but larger casks give greater complexity, richness and depth,” says Rachael.
As ever it’s a case of matching the cask influence to the house style.
“For Talisker Port Ruighe, we finish the spirit in ex-Port hogsheads.
“When this expression was in the innovation stages around eight or nine years ago, we also looked at larger port pipes (c.650 litre), but found the flavour given by the smaller casks worked better with the Talisker distillery character,” says Maureen Robinson, master blender, Diageo.
Rachael provides further examples of utilising a finish. “Glendronach new make spirit has a robust ‘winey’ character with layers of dark fruit and lots of berries, and maturing Glendronach in Ruby Port casks amplifies the house style with intense bramble fruit.
“Glenglassaugh new make spirit is more buttery, with clotted cream and plenty of luscious fruit flavours, using a Ruby Port cask with this transforms it into stewed fruit with cream, fruit jam and dark chocolate, creating a dessert-like quality.”
Full-term maturation is a rarity, though Kilchoman has released two expressions matured exclusively in Ruby Port casks.
“The three year old had a blackberry and strawberry vibrancy, with sweetness and lemon, citrus in the background. The six year old had more depth, with rounder, riper summer fruits, and the lemon citrus was even further in the background.
“The phenolic character was also noticeably mellower than in the three year old,” adds Anthony Wills, managing director, Kilchoman.
The tradition of using Port casks in Scotland stems from practicality.
Port was originally exported in casks, and bottled in Britain, resulting in empty casks that were sold on to Scottish distillers.
The usual choices for malt whisky are Ruby and Tawny Port casks.
Both are a blend of wines from different years, with Ruby Port essentially showing ripe fruits and Tawny Port delivering a richer, dried fruit edge.
“The older the Port aged in the cask the richer the fruit notes it contributes to malt whisky,” says Richard. With so much on offer will we see more malt-Port liaisons? Maybe. What we do know is that at least for now Port casks are an established fixture. “Port casks only account for around two per cent of our stock profile across our three malts, but it’s a cask type I’ll always have and use for enrichment, either in its own right or woven into a recipe,” says Rachael.
Glen Moray’s 21 Years Old Portwood
Richard Paterson in the sampling room