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You are here: Home --> Forum Home --> Brewing Forum --> Brewing Discussion --> Calculating oaking rates: oak cubes vs. wine barrels

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chino_brews
Charter Member
Eden Prairie, MN
300 Posts


How many oak cubes in a 5-gallon batch correspond to the oaking rate of having a full wine barrel?

This blog post seems to indicate that a 59-gallon wine barrel corresponds to a barrel surface area to volume of 54 square inches per gallon.

It seems like an oak cube averages around 0.75 square inches each (they average around 0.5" x 0.375" x 0.25" based on my samples). So 72 cubes per gallon? That is about 10-11 oz. per 5 gallons and seems way out of line with recommended usage rates.

This article from MoreWine suggests that 2.5 to 3.0 ounces per gallon corresponds to "new barrel" extraction rates.

What am I missing here?




Posted 34 days ago.

homebrewdad
Charter Member
Birmingham, AL
2474 Posts


Where's @Matt when we need him?



Posted 34 days ago.

Matt
Charter Member
Normal, IL
341 Posts


So I typed out a crazy long message with tons and tons of math in it, which essentially came down to "those numbers are mostly correct, sorta" and then listed the reasons why I am still an advocate for the rates I recommended and reasons I think the numbers aren't accurate to simulation. 

But hey, I said "Damn" in the message, and so when I sent it to myself to finish at the university the filter caught it and got rid of it. Sigh. 

Anyways, here is what we are missing (in my opinion). 

The surface area of a cube isn't equal to the surface are of the wood because those surface areas don't exist in isolation. With a barrel, you have the rate of oxygen diffusion, which is far less when it comes to buckets and carboys. The amount of oxygen exchanged by cubes is negligible, close to zero.

Plus, cubes are surrounded by beer, this means that the beer will penetrate the cube, there is a finite amount of reactions that can take place because those cubes exist INSIDE the wort, so eventually all that can be done with them will be. Barrels don't act that way, since the beer can only sink so far in to the staves, and even then there is the constant contact with oxygen and whatever else happens to be in the air.

For our purposes though, this should just be in terms of oak flavor and the surface area of wood. Problem is, I'm not convinced those are equal either. I am going to send out some emails today and I'll get back to you, I want to know the answer to this as well, but I am 100% against the 11oz per five gallons numbers. 




Posted 34 days ago.

mchrispen
Bastrop, TX
485 Posts


Something else to consider. Ethanol content affects vanillin extraction significantly, not sure with other tannins. So those estimates were from a winery - assume 10-14% ABV in wine, their extraction rate may be higher than in a 8-9% beer. I know using oak beans with high-proof ethanol, the color and flavor compounds are extracted relatively quickly, more quickly when agitated, but very different than aging in a real barrel.

As Matt notes - there is a lot of difference between using a barrel, where O2 becomes a larger player. Temperature is also in effect as heat and cold pump liquid in and out of the pores of the wood. I have soaked oak beans in wine (or gin or bourbon or tequila), using a mason jar with a vacuum sealer. I get seem to get more of the liquor flavor into the wood this way. Then add the beans to a beer and sometimes the soaking liquor as well to taste. I tend to fall in the 2 ounces of beans per 5 gallons range for beer.




Posted 34 days ago.

Matt
Charter Member
Normal, IL
341 Posts


mchrispen, that's the same amount I use as well. 

Second fun fact, and Chino I think this is closer to the area you're looking for an I sort of hinted at it in my initial response but didn't really pin it down. 

Penetration. 

A cube gets completely penetrated, all sides, so through and through. Beer only penetrates 6mm into the staves of a barrel, but they will penetrate the entire cube. That's where the additional flavors come from, and why we use less cubes (per surface area) than a barrel. We weren't accounting for a whole bunch of wood that is still involved in the process. 






Posted 34 days ago.

Matt
Charter Member
Normal, IL
341 Posts


Oh man, I forgot about the grain of wood! Cubes have end grains, while staves in a barrel are typically side grains! Liquid penetrates the end grains of wood WAY faster than the side grains, up to 8 times faster. So cubes have more surface area than the calculation, because of penetration, and they also are penetrated 8 times faster than staves! Cheers to Chris from Northern Brewer for reminding me of this!



Posted 34 days ago.

jeffwhit
Aalborg, Denmark
2 Posts


So, I have a Lambic Solera going, and a saison that was primaried with Wallonian and Trois, and in a couple days will have a long secondary fermentation with Crooked Stave and Jolly Pumpkin dregs. The lambic is definitely getting oak, (and possibly wine) the saison maybe- is 2-3 oz per gallon still a good rule of thumb then? Both beers should be about 5.5% ABV.






Posted 34 days ago.

Matt
Charter Member
Normal, IL
341 Posts


2-3 ounces is a bit much in my opinion. If you are using cubes (which I think you should) my rule of thumb is one-two ounces of cubes for two-four months. When in doubt, less wood and more time. 



Posted 34 days ago.

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