Fermentation vs Aging Oak

updated 09/11/2024

A common point of confusion among new winemakers is the usage of oak adjuncts in the winemaking process. Some are added before fermentation, some after fermentation, and there are numerous types: dust, shreds, chips, cubes, spirals, and staves. It’s not surprising this is information overload.

Types of Oak Adjuncts

I addressed the topic of oak adjunct types in a different post. I suggest you read that one before continuing with this post.

Fermentation Oak

Fermentation typically occurs during a short timespan, typically 5 to 10 days. While fermentation can more or less time, 5 to 10 days is accurate enough for the purpose of this post.

During fermentation, oak with more surface area is normally used, as the wine has a short period in which to absorb constituents from the oak. Kits typically include dust and/or chips, and I use shredded oak. Products with less surface area, such as cubes, don’t work as well.

The substance most extracted in this short period is oak tannin, which is referred to as “sacrificial tannin”. Post-fermentation, as the gross lees (fruit solids) precipitate, a certain amount of tannin precipitates with it. Without fermentation tannin, the natural grape tannin drops. If oak tannin is present, it drops instead, preserving the grape tannin.

Tannin helps preserves color (important in red wines), enhances mouth feel and fruit, removes vegetal aromas, and reduces astringency.

Various sources stated that fermentation oak doesn’t directly affect flavor. However, an experiment I conducted during the Fall 2020 made me question this — I fermented 2 different batches of Merlot with American and French medium toast shredded oak, respectively. Immediately post-fermentation the two wines were distinctly different, which made me question the assertion about oak not directly affecting flavor. However, this difference faded with time, so it appears correct.

Aging Oak

Wine can be aged with oak products, either new or used barrels, or oak adjuncts. This oak can have a strong impact on aroma and flavor, and takes place over a longer period of time, ranging from a few weeks to years.

Generally, coarser oak adjuncts are used, to avoid over-oaking the wine. It’s very possible to let a wine absorb too much oak, so much that the oak aroma and flavor overpower the wine and make it unpleasant.

In general, dust and shredded oak are not used for aging as the greater surface area is more likely to impart too much oak into the wine. If used, the taste must be monitored more carefully.

Chips and cubes were used most commonly during previous decades, as they were easy to manufacture and commonly available.

Spirals and staves are now common, and have the advantage of being very easy to use. They are often suspended in the secondary container using nylon fishing line and can be easily extracted.

Other adjuncts can be placed in muslin bags, but the narrow mouth diameter of carboys makes it difficult to get the products in and out. If added without an enclosing container (e.g., bag), it’s necessary to rack the wine to remove the oak.

How Long To Keep Oak In

It’s generally agreed that oak adjuncts are expended, e.g., the oak character is all extracted, after about 3 months. Leaving the oak in longer has no ill effects, and may be beneficial. Several members of WineMakingTalk have noted that wines with the oak adjuncts left in longer tend to be smoother, so extended aging with oak adjuncts is beneficial.

I have neutral barrels, meaning the oak character is long since extracted, so the barrels act as containers and provide a concentrating effect as some water and alcohol evaporate through the wood. This concentrates the remaining constituents in the wine, making it deeper in flavor and body.

To provide oak character, I add oak cubes, which are left in the wine for typically 12 months.

Some add oak for very short amounts of time, to get just oak character. If that is desired, it works, but in my experience it’s short sighted.

How Much To Use

We now know “what” and “why”, so the remaining question is, “how much?”.

This question has no single answer, as the answer varies by grape variety, wine body, and personal preference.

Heavy reds can handle more oak than lighter reds, as the heavy reds have more flavor and body that the oak has to compete against. Whites have even less body and flavor, so they can handle even less. Some whites such as Chardonnay and Sauvignon Blanc can handle oak, while others have a strong mismatch between their natural flavor and the oak.

Fruit wines? Heavy fruit wines such as Elderberry can be nicely improved by oak, while very light fruit wines are easily overpowered, as are some white wines.

Let’s confuse the situation more by considering that some folks LOVE oak flavoring, while others don’t.

Generally speaking, I recommend the following amount of oak (in ounces) per 19 to 23 liters of wine:

Note: Always go light on oak. It’s far easier to add more than it is to take some out.