As I discussed previously, oak will enhance the flavour of wine.  Much of that flavour imparted by the oak occurs naturally from the raw wood but ‘toasting’ the inside of an oak barrel will further enhance these flavours.

After a barrel is made its inside can be exposed to fire in order to toast it. This is done either over an open flame or by using a hand-held torch. The fire caramelizes the wood’s natural sugars and brings out complex compounds. From this, the wine will take on flavours that are toasty, charred, spicy and sweet depending on the amount of time the wood is toasted.

A lightly toasted barrel will be exposed to flame for about 25 minutes while a heavily toasted barrel may get up to one hour of flame exposure.  Generally, the heavier the toast, the stronger and more varied are the revealed flavours.

Light toasting will impart flavours of subtle vanilla, coconut, caramel, clove and cinnamon.  Medium toasting provides stronger vanilla, honey, caramel, toast, coffee and cocoa flavours.  Finally, heavy toasting provides vanilla, espresso, smoke, crème brûlée, butterscotch, toffee, coffee and molasses flavours.

Oak will interact with wine differently depending on the grape variety. Oak may provide hints of chocolate to a Merlot or vanilla or coconut to a Zinfandel. White wines aged in oak typically develop flavours of vanilla, baked apple, caramel, honey, toasted marshmallow, or buttered toast.

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Oak has a major impact on the flavour of the wines we drink; whether it is absent or present; and if it is present, whether it be new oak, old oak or neutral oak.  When wine remains in contact with wood during the fermentation and aging process, changes take place due to extractable organic compounds.  These biochemistry effects translate into the wine’s aroma and flavour.

All oak wine barrels are toasted when they are made.  Toasting is when the inside of the barrel is exposed to a flame for a specific time and temperature depending on the style of barrel.  I will talk more about the toasting process in an upcoming post.

The impact of the toasting process declines as barrels age with use.  New oak creates aromatic and flavour complexity in the wine whereas old oak becomes more neutral year after year.  Some winemakers use a mix of new and old oak throughout the cellar in order to achieve their desired wine characteristics.

New oak influences red wines differently than white wines. In reds it will adjust the tannic structure while in whites it will open the aromatics of the wine.

The use of a high percentage of new oak barrels can create flavours of toast, vanilla, baking spices, coffee, caramel, maple or smoke.  Neutral barrels no longer generate these flavours or aromas.  New oak is also used to accelerate the softening of high tannin wines like Cabernet Sauvignon.  They can produce a more rounded wine at a younger age.

While neutral oak barrels no longer provide flavour, they still play an important role as they introduce oxygen to the wine.  This oxygen seepage has a big impact on the natural chemical conversions that wine undergoes during maturation.  Neutral barrels help maintain the fruit qualities of more delicate wines and soften wines that have a high amount of tannin.

The size of the barrel affects the oak’s impact on the wine.  The larger the barrel, the less oak lactones and oxygen that are transferred into a wine.  Thus, there is less impact on the flavour and aroma.  Barrels are normally 225 litres but can be as large as 1,000 to 20,000 litres.

The typical winemaking lifespan of a properly maintained barrel is around five years.  However, this may vary depending on the appellation, the type of wine and whether the winemaker is using the barrel for profile influence, oxygenation or storage.

Maintaining enough new oak on hand can be a challenge as there are only a limited number of new barrels available for purchase each year.  As well, the cost can be prohibitive as the price of one barrel can range from a few hundred to a few thousand dollars.

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This is the first of a three-part series on the use of oak in the wine-making process.

It’s a well-known fact that oak has become the most accepted way to affect the taste of a wine.  When added to wine, oak combines with the flavours of the grapes to create a wide variety of incredible tasting wines.

Most the world’s finest wines are aged in oak barrels, with French and American oaks being most commonly used.  However, Russian and Eastern European oak are also used, especially in Europe.  All wine barrels are made from white oak but the characteristics of the barrels vary greatly depending on the source of the oak.

French Oak

French oak is historically found in the forests of eastern and central France.  It has more tannin than the other oaks so lighter grape varieties, such as Pinot Noir, are well suited to tannin-rich French oak.  French oak has a tighter-grained wood structure which exposes subtler tastes like aromatic spices, cocoa and coffee. French oak grain is less coarse, contributing to wines with subtle, spicy and smooth, satiny or silky qualities.

American Oak

American oak is twice as dense as French oak, bringing greater spice and wood sugar compounds that slowly extract and fill out a wine’s body.  American Oak has a loose grain and is heavy in lactones, which creates flavours like coconut and banana to finished wines.  It can also provide an impression of a bit of creaminess and a hint of vanilla in wine.  American oak contains a lot of hemicellulose¹, which when charred will break down into wood sugars, allowing for some caramelization. 

American oak is widely used in Spain to make Tempranillo. American oak barrels can weigh twice as much as French oak barrels but cost about half the price to purchase.

Russian and Eastern European Oak

Eastern Europe has a vast supply of oak trees. Hungarian oak is richer in eugenols, which impart spice, and tends to create a slightly richer mouthfeel with substantial tannin.   Caucasian oak, on the other hand, releases less tannin and aromatics, which is better for lighter wines desiring a straight-up expression of the grape itself.

Russian oak is used widely throughout Europe. Slavonian oak is used in a variety of Italian wines.  It is known for providing less tannin and more sweetness to the wine.

¹ According to ScienceDirect.com, “Hemicelluloses are typically defined as components that can be precipitated by ethanol after extraction from the cell wall by dilute alkali. In such procedures they are extracted after depletion of the pectin content of the walls by aqueous solvents and calcium chelators”.

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What is it?  Can you taste it?  How much acid is in wine? Is it necessary to have acidity? These are many of the commonly asked questions about acidity in wine.  Understanding acidity helps us to identify which wines we like and to better be able to pair wines with our favourite foods.

If you taste a wine that you find to be refreshing yet slightly tart, this is the result of dominant or prevalent acidity.  When someone says a wine is crisp, bright or fresh, it means the wine has great acidity.  Although these terms are most commonly referred to when discussing white wines, some red wines can be crisp, bright and fresh as well.

The common misconception is that some wines have acidity while others don’t, but all wines have acidity. Even in a wine such as Cabernet Sauvignon, which is normally thought of as deep and mellow, acidity helps blend all the other flavours of the wine. If a wine has no acidity at all, it tastes dull and flat. It is acidity that makes the wine appeal to your taste buds and enable you to recognize all the various flavours.

Acids are one of the four fundamental traits in wine; the others are tannin, alcohol and natural sugar. Acidity gives a wine its tartness. The amount of acidity varies depending on the type of wine.  Most range from 2.5 pH to about 4.5 pH on the acidity scale.  The lower the acidity the higher the pH level.

There are several different types of acids found in wine. The most prevalent acids are tartaric acid, malic acid and citric acid.  The amount of these acids in your wine will determine how much of a puckering sensation you experience in your mouth.

In wine tasting, “acidity” refers to the fresh, tart and sour elements of the wine which are evaluated in relation to how well the acidity balances out the sweetness and bitter components such as tannins.

The natural sugar content in a wine can disguise the acidity, making the wine seem smoother with a reduced puckering sensation.  An extreme example of this would be to compare the juice of a lemon with a glass of Coca-Cola.  Both have a pH acidity level of 2.5 but the intense puckering sensation of the lemon is not felt at all when you take a sip of the cola.

Acidity acts as a buffer to preserve the wine longer so high acid wines are more likely to improve with age. The stability of high acid/low pH wines helps during aging. Conversely, high pH wines are more prone to contamination. Microbes or other unstable components can make high pH wines appear hazy.

The type of acid present in a wine can also affect our perception of sourness and the puckering sensation. During the aging process, a wine’s malic acid is often converted to lactic acid, which results in a smoother, less tart-tasting wine.

Another facet of wine that can be confusing is a wine’s total acidity. This is something that’s often noted on a wine tech sheet or in the wine maker’s notes.  Total acidity tells us the concentration of acids present in wine, whereas the pH level tells us how intense those acids taste. For example, if you have a wine with 6 grams per litre total acidity and a pH of 3.2, it will taste more acidic than a wine with 4 grams per litre total acidity with the same pH level.

A higher acid white wine will be lemonier in flavour, making your mouth water and pucker a little.  Red wines with higher acidity are more likely to be a bright ruby colour, as the lower pH gives them a red hue. Higher pH, less-acidic red wines can take on a blue or purple hue. Wines with lower acidity can also take on a brown colour because they’re more prone to oxidation. It may not be as noticeable in red wines but can be off-putting in young white wines.

Unripe grapes have high acid levels that decreases as they ripen. Grapes grown in cooler climates usually contain higher acidity because there’s less warmth and sunshine available to increase grapes’ sugar and pH levels.

When pairing wine with food it’s helpful to consider the tastes found in a dish, whether it be sweet, sour, bitter, salty, fatty, etc. With a wine having a higher level of acidity, you’ll notice that sweetness, saltiness and fat balance the sour taste of the acidity.

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A wine barrel has become one of the most recognized symbols associated with wine. As a society we have romanced the wine barrel to the point where we have turned it into tables, benches, planters and candle holders.  Case in point, I have two barrels in my wine cellar as leg supports for a table and I have a candle holder made from a barrel rib on my bar.

The Romans discovered that oak could be more easily bent into the traditional barrel shape than palm wood; the oak only needed minimal toasting and a barrel could be created much faster. Oak was also the most abundant in the forests of continental Europe and its tight grain made it waterproof.

The Romans learned that oak has a tendency to soften and smooth the flavour of wine and provide it with a more complex taste.  Slight toasting of the wood added scents such as cloves, cinnamon, allspice or vanilla, as well as flavours such as caramel, vanilla or even butter.

Today wine barrels are made from a variety of materials; European oak (often referred to as French oak), American white oak, stainless steel, aluminum and HDPE (high-density polyethylene) plastic.  These barrels typically come in 3 standard sizes:

• Bordeaux type – 225 litres
• Burgundy type – 228 litres
• Cognac type – 300 litres.

Barrel aging is the main element of what is referred to as the élevage process, which is a French term meaning “raising” or “upbringing”. This is what occurs to the wine between fermentation and bottling.  The wine’s élevage can last for a few months to many years, during which time the wine’s flavours integrate and mature.

The winemakers’ choices during the aging process include how long to age the wine for and how much to manipulate it. which has a major impact on the taste of the finished product. One of the most important choices is what type of barrel to age the wine in.

When oak barrels are manufactured they are toasted over a fire to either a light, medium, or dark toast level. New barrels with a light toast will give lots of vanilla and caramel notes, while a darker toast will give smoky, roasted aromas.

An oak wine barrel’s age and size affect the amount of oak flavor that will be transmitted to the wine. Smaller barrels impart more oak flavor because they allow more contact between the wood and the wine. Oak barrels lose their flavour compounds with use so they must be replaced every few vintages.

In addition to adding oak flavours, new oak aging changes the tannin structure of red wines. Tannins from the wood barrel transfer into the wine, giving it a stronger structure. This contributes to a wine’s aging capability, or longevity in the bottle. The wood also helps stabilize the tannins from the grape skins, giving them a silkier texture.

After a few years of use, the oak will no longer provide flavour or tannin to the wine. The older barrels still allow for slow oxygenation, so they can be used to age wine that needs to mellow without the addition of oak flavouring.

Oak influences both red and white wines by adding the aroma of:

• Vanilla
• Caramel
• Baking spices like cinnamon, clove, nutmeg
• Coconut (especially from American oak)
• Dill (especially from American oak)

Red wines may also present additional aromas of:

• Smoke
• Chocolate
• Coffee
• Toffee
• Burnt sugar

Steel barrels, on the other hand, add no flavour to the wine.  Steel simply stores the wine for a few months while it stabilises and the grape flavours integrate. Steel barrels also don’t let any oxygen come into contact with the wine. This kind of aging helps wines retain the fresh fruit aromas that disappear when exposed to oxygen.

Stainless steel aging is used for wines that would not benefit from the addition of oak flavours or the softening effect that oak has on tannin. It is used for white wines not having tannins to manage. Stainless steel is the usual choice for aromatic and semi-aromatic white grapes including:

• Albariño
• Unoaked Chardonnay (often aged in oak as well)
• Gewürztraminer
• Grüner veltliner
• Pinot grigio
• Riesling
• Sauvignon blanc

For red wines, stainless steel is a good choice for lower tannin, fruity grapes such as:

• Baco Noir
• Gamay
• Grenache

Red wines aged in stainless steel are straightforward and juicy, with no oak flavours obscuring the flavours of the grapes.

Stainless steel aging is significantly less expensive than using oak because unlike oak barrels, steel barrels can be reused indefinitely and are much easier to clean. Stainless steel aging also takes less time than oak aging which saves winemakers crucial space in the wine cellar.

Since oak barrels can be used only two or three times for the purpose of adding flavour to the wine, the cost of buying new barrels is built into the higher prices of oak-aged wines. Some producers try to mimic the flavours of oak aging by adding less expensive oak chips to wines that are aged in stainless steel vessels. Oak chips add vanilla and spice notes but have no effect on a wine’s texture like oak barrels do.

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