Chemistry of Batch Sparging

Posted on 08.29.09 9:59PM under All-Grain, Brewing, Stories

I made beer today for the first time in a few months. Oktoberfest is coming up and I need beer for the O-fest party. One batch of Yachtoberfest 2009 and one Fisher Cat Wheat should do the trick.

My friend Jeremy was here to assist with the brewing. He is a chemistry expert. This looked to be a mutually beneficial day. He’d get to learn about the practical chemistry orchestrated by the various steps involved in turning grain into beer. I’d get to ask him all sorts of scientific questions about the process in real time, complete with discussion and maybe even some experimentation.

Things started a little slow, as I didn’t jump in from the start as task-oriented as usual. But that’s the thing about having a helper. They can help you. So I knew that Ididn’t have to worry about getting all the ingredients measured out ahead of time, because Jeremy could do it. I didn’t have to be too concerned about synchronizing actions of the first and second batch, because Jeremy could take care of one of the tasks whenever there were two urgent things going on at the same time.

Revelation. Reveal the Truth.

The biggest revelation of the day was regarding sparging. This is the step in the brewing process when you rinse the grains. After soaking the crushed grains in hot water to extract fermentable sugars (mashing) you drain off the freshly produced sugar water that will one day become beer (wort) and rinse all the sugars off the grains until you get a full brew kettle. I have always fly sparged, meaning that I continuously add water to the top of the mash as I drain it out the bottom. I thought this was supposed to be the best way to get the most even extraction from the grains.

Enter Mr. Chemistry. I guess these chemistry guys know a thing or two about efficient extraction. I think there could be a crude joke in there, but I can’t find it. Turns out you have a lot more control over the process if you completely drain out the wort and then add only enough water to cover the grains, and then drain it all and rinse it again until you’re done. In other words, batch sparging is the best way to get the maximum extraction efficiency from your mash.

The idea is that the water in the mash is roughly uniformly distributed with respect to sugar concentration. Even though the water entering at the top is less sugary than the water at the bottom, you lose something with a continuous flow. Rinsing with sugary water is less effective than rinsing with clean water. When you drain all the wort and then refill with clean water, your rinse is that much more effective.

Sweet Efficiency

I batch sparged the O-fest, and ended up with 85% extract efficiency instead of my common 65% that I’ve become accustomed to with my fly sparging. So much for a 5% ABV O-Fest. Looks more like 7%. Cool!

For the Fisher Cat, I didn’t exactly batch sparge, but I coordinated it so that when the kettle was full there would be no wort left in the mash. Normally I leave a gallon or two in the mash. Turns out that the water that I was leaving in there was full of sugars that I should have been able to collect in the kettle. Even with this batch-fly combo, I got a cool 75% efficiency!

This changes my life. Well, maybe that is a little overstated. But it does mean that I am no longer limited to 4.5-5% ABV all-grain brews. My 11 pounds of grain will now get me more like 6-6.5%! This prevents me from needing to use extract to get my beer to that point, and saves me extract when I want to go higher than that. This makes me want to try a thicker mash with more grain in the same puny 5-gallon cooler. How far can I push this thing?

Be Cool

Another thing that came up was my chilling technique. I realized, thanks to the lens of another’s eyes, that I was really not using two very simple and available methods to drastically improve my wort cooling performance: a pre-chiller and a ice water bath.

I can easily use a pre-chiller coil. I have two unused copper coils and plenty of tubing and hose clamps on hand. All I need to do is put one of these coils, immersed in ice water, in line with my existing chiller after the hose and before the kettle, and I will have ice cold chilling water all year around.

I have everything I need to make an ice bath for the kettle. I brew in a 30 quart kettle. And I have a 10 gallon kettle that I don’t even use! The boil kettle fits in there easily. If I just fill the big one with ice and sit the brew kettle in it while chilling, it will be as if it is ice cold outside the kettle all year round, too! No longer will I have to long for the short snowy days of December when the wort is down to 60 in fifteen minutes as I sit in August chilling wort for an agonizingly long half hour that still leaves the wort at 80.

Conclusion

Brewing is great. Brewing with friends is even better. Brewing with smart friends knowledgable in things that can help your brewing is awesome. And the funny thing is that Jeremy doesn’t even drink beer. But he did taste both worts.

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