Bite-sized learning on everything and anything relating to wood, casks and the maturation of spirits by Dr. Martin Purvis.
I wanted to learn more about sherry…..
…so i could understand more about the impact on barrels and their use in spirit maturation. I wanted to shine a light on this misunderstood category and its link to the distilled spirits world.
Sherry is fortified wine from Southern Spain (Jerez). Producers use distilled grape alcohol to increase the strength of the product so that it ranges from 15-20% abv.
The higher strength historically allowed the wines to travel and keep for much longer than normal table wines.
There are three main types
1) Dry sherry wines – like Fino
2) Naturally sweet wines- like PX (Pedro Ximenez)
3) Blends of the above (Dry to Sweet depending on the blend).
Colour and flavours come from the wine and its ageing in oak barrels. The barrels act as containers and are used again and again to mature wines over time. The presence or lack of access to oxygen in the barrel (mostly at the headspace /liquid interface) determines more of the details of the style and character of each variety of sherry.
Old butts or vessels do become available and once reconditioned and repaired are great barrels for spirit maturation.
They are limited in numbers and have had many low strength extractions on the wood over time. Flavour active compounds from the wines are key here along with some wood compounds that are left behind by the wines solvent action.
This causes challenges for the big producers of sherry matured spirits who need thousands of butts which are consistent and regularly available – in order to keep growing their production.
The production process is complex as is the differentiation of sherry types.
At the dry end of the spectrum is Fino.
It owes its character due to ageing entirely without oxygen under a covering of yeast inside the sherry butts – called flor. This is termed biological ageing and prevents oxidisation of the wine.
The wine has a very pale colour and its flavours are derived from interaction with the flor.
Fino is fresh and crisp on the nose with almond notes that are characteristic of the yeast with a very dry flavour and low acidity. Their alcohol content is usually about 15%. Too much alcohol kills the flor and changes the wine style so these wines are lighter than other styles.
At the other end of the dry spectrum sits Oloroso Sherry…..
It is aged without the covering of flor so is exposed to oxygen and oxidation of the wine.
It is typically much stronger than fino – at 18-20% abv – and this higher strength of wine prevents the yeast flor from forming – alcohol kills more organisms the higher you go!
Oloroso therefore has much Darker colour (due to oxidation)
It typically yields aromas that include nuts, tobacco, spices, leather and spicy wood.
They are powerful wines on the palate with more alcohol and mouthfeel. My local wine shop stock some great marques although I have to confess to loving the Cream rather than the dry varieties.
The sherry wine used in seasoning new oak butts becomes undrinkable after use. The levels of extractives and in particular tannins that it removes from Spanish oak make it into something that wouldn’t be too tasty.
The sherry that we drink is stored in older butts that have had many fills and provide little in the way of oak flavour to the sherry. The colour and flavour in sherry mostly comes from the method of manufacture and also how exposed the wine is to oxygen during maturation in the cask.
A protective flor or yeasty covering develops in sherries that are at lower strengths. This provides an anaerobic maturation (without access to oxygen in the headspace of the barrel. The higher strength of some sherries kills the flor and prevents it from forming – allowing aerobic maturation in the presence of oxygen.
The seasoning wine is not wasted – with onward processing into sherry wine vinegar and balsamic style sauces which are fantastic products in their own right.
by Master of Wood and Barrel Expert Dr. Martin Purvis, at Smart Distillery Solutions, servicing clients such as Kelvin Cooperage.
Qualifications: BSc/PHD Geology, MSc Brew/Distilling, MBA Luxury Brand Marketing and Family Business
Background: Martin has worked for nearly 20 years across the spirit drinks industry in a variety of roles from Technical Support, Compliance, Food Safety, HMRC, Blending, Procurement of raw materials, Barrel Procurement, Maturation improvement, grain storage and merchanting, used and new barrel sales, customer relationship management, new business development.
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