How To Sanitize An Oak Barrel

You’ve decided to dip your toes in the art of winemaking, and you want your wine to meet or surpass Bordeaux’s quality. 

The only thing standing in your way is the chore of caring for and maintaining your oak barrel(s). Oak barrels are usually perceived as high maintenance, and the potential for spoilage issues despite caring for them might be a deterrent.

However, with a good routine, some basic skills, and experience in barrel care, this task becomes an easy and fun part of your winemaking endeavor. Additionally, oak-aged wines have more benefits that outweigh all the effort and risks in oak barrel care.

Here are some guidelines that you’ll need to remember on caring for and sanitizing your oak barrel.

Purchasing an Oak Barrel

When buying an oak barrel, whether it’s new or used, the first step is to check for the quality. You need to inspect the interior and exterior and assess its quality while checking for any potential issues. 

An excellent way to visually inspect the barrel’s interior is by inserting a light source such as a torch through the bunghole. Doing so helps you identify any obvious wood defects, excessive wood curing (that might have resulted from over-toasting during manufacturing), and wide joint gaps. 

Manufacturers usually toast oak barrels in open fires. Therefore well-toasted wood needs to have a smooth finish with an even, brownish color and should not be charred.

It’s easy to spot charred wood as it typically looks damaged. You can also quickly identify it from its deep dark brown color that almost looks black. Visually checking the exterior should reveal narrow and tight stave and head joints.

Ensure that the manufacturers properly fastened the hoops and tapered the bunghole. The bunghole should also not be damaged as it could pose a potential spoilage problem. 

An old oak barrel may have a crack originating from the bunghole. The damage may cause your wine to undergo excessive oxidation, thus altering your drink’s taste and aroma, resulting in a flat wine.

How to Clean an Oak Barrel

As your wine soaks into the barrel wood, it gives room for microorganisms to grow. As such, it’s crucial to first clean the barrel before sanitizing it. 

Barrel cleaning helps in getting rid of any gross solids and colors. It also helps remove any tartrate coatings on the barrel’s surface that may prevent sanitization treatments from reaching into the wood.

The best way to clean a barrel is through a several-rinse cycle. For this, you can use a barrel washer. Cleaning your barrel helps you prevent any growth of spoilage organisms.

 Wash your barrel with water until any deposits have dissolved. Repeat the procedure several times until you’re confident the deposits are no longer there.

Fill the barrel with warm water and let the water sit in the barrel overnight to dissolve the deposits quickly and efficiently. You don’t need harsh chemicals if you’ve been properly maintaining and storing your barrel.

Using harsh chemicals is frowned upon as it strips your barrel of the oak extract and damages the container itself. 

For example, soap can soften your wood, while soda ash will remove the oak flavor that some vintners use to enhance the wine’s taste. It’s always best to try and detect the issues by sight or smell.

How to Sanitize an Oak Barrel

Sanitizing your oak helps you get rid of bacteria that might remain in the barrel even after cleaning. There are three ways to sanitize a barrel:

Using Steam

Research shows that steam is an effective method of barrel sanitation. Using steam helps you remove yeast from the barrel’s internal surface, and it reaches up to 2mm of the staves’ interior. 

Other researchers suggest steaming for a minimum of ten minutes to get to a depth of 8mm using temperatures greater than 57.5°C.

Using Hot Water

A hot water treatment is an effective means of cleaning an oak barrel and helps eliminate acetic acid bacteria. Research shows that treating oak wood with 85°C water for at least 20 minutes successfully removes these bacteria, Brettanomyces, and yeast from the wood at 5-9mm depths. 

By Using Special Chemicals

Sodium Bisulfite solution is an excellent chemical option for sanitizing your oak barrel. Simply fill half of the container with water, dissolve the instructed amount of Sodium Bisulfite in water, and pour the mixture into the barrel. Mix the recommended amount of Citric Acid solution as well and pour it into the container.

Tightly close the barrel and shake it or roll it around to mix the storage solution well. Finish by filling the barrel with water and sealing it tightly. If you don’t intend to use the barrel any time soon, constantly check the water, filling the barrel each time. 

Whenever you want to use the container, just pour out the water and rinse the barrel. Fill it with fresh water and leave it overnight. Rinse out the water several times the next day, and your barrel will be ready to use.

Other Specialized Treatments

Winemakers in the past used to shave the charred surface and refire their barrels as a sanitization method. However, studies suggest that these aren’t the most effective ways of getting rid of all harmful yeast because of the yeast’s penetration in the wood.

What’s more, physical techniques such as dry ice blasting and shaving need you to either remove the head stave or deconstruct the whole barrel, which is more labor-intensive than other sanitization techniques.

Instead, researchers suggest using high-pressure ultrasound treatments in conjunction with other sanitization methods like hot water to effectively kill any harmful yeast in barrel wood. 

The only downside to this form of sanitization is that it requires specialized treatments. However, combining high power transmission and heat at 60°C for six minutes penetrates the barrel wood up to 9mm in depths and eliminates viable Brettanomyces yeast.

Frequently Asked Questions

How do I know the sanitization process worked?

After sanitizing your barrel, you can test its efficacy by adding about 4L of sterile water to your barrel. Preservative-free filtered wine also works in this case. 

Roll the barrel for a few minutes from side to side and leave it for 24 hours. Then sample and test the liquid for any harmful microorganisms.

How should I store my oak barrel after sanitizing it?

If your barrel is new, store it in a clean area with 65-75% humidity. If it’s used and you don’t intend to fill your barrel with wine for a period of time, you can store your barrel dry or wet, preferably wet. Dry storing the barrel involves burning sulfur to produce sulfur dioxide. 

Alternatively, you can fill the barrel with sulfur dioxide gas. Rinse the barrel after one month of continual dry storage and fill it with cold water, leaving for 48 hours to hydrate.

Wet storage involves filling your oak barrel to one-tenth capacity with an acidified sulfur dioxide solution. It’s important to note that this liquid evaporates from the barrel over time. Therefore, maintaining one-tenth capacity is ideal for helping your barrel remain wet and preventing leaks.

Remember to rinse the barrel after storage, as any remaining sulfur dioxide can negatively impact your wine. 

Residual components of the acidified solution inhibit yeast growth and increase the risk of sulfide formation. It can also affect your wine’s taste and quality if not rinsed away.

You can also store the barrel using water. Simply fill your barrel with water and constantly check it, refilling if necessary. If you live in a warm, dry area or don’t have quick access to hot water, you can regularly wet your barrel’s exterior with a damp cloth.

Do I need to clean my barrel frequently?

If you’re barrel aging the same wine in subsequent batches, then you won’t need to clean the barrel between every batch. If you plan to age different wines with each batch, you should clean the barrel each time. 

It’s noteworthy to point out that frequently cleaning your barrel lessens its lifespan and reduces its effectiveness. It’s therefore recommended to have different barrels to use for other wines.

How long will my oak barrel last?

With proper maintenance, your barrel could last you eight or even ten years if you’re lucky. The critical thing to remember is never to allow your barrel to dry out.