Saturday, December 27, 2008

A Mystery Solved

Life is full of mysteries, great and small. A small mystery for me has been why coffee made in a French press requires so much more coffee to achieve the same strength of brew compared to a drip coffee maker. It just seemed intuitive to me that if you take nearly boiling water, dump it straight into the ground coffee and let it steep, you have the maximum possible exposure to the surface area of the coffee and therefore you're going to get the strongest possible brew. But it just ain't so. In fact, you have to use almost twice as much coffee in the press. Hmmmmm.

Well, I was discussing this mystery with a couple of my nephews the other day and in the context of that conversation one of them asked a question about beer making (there had to be a connection, to make it onto this blog, right?) All of a sudden, enlightenment! The mystery was solved.

As I've laid out before on this blog, beer is made by adding hot water to ground malted barley (a process called mashing) and then, after the resulting activated enzymes have done their work to convert the starches in the grain into sugar, the sugar is washed away and fermented. That washing process is called sparging. Broadly speaking there are two main sparging techniques--batch sparging and fly sparging. In batch sparging you drain off that initial infusion of hot water from the malt, then add another slug of hot water, stir to dissolve more sugar, and run off again. In fly sparging the brewer sprinkles hot water onto the malt at a steady rate and collects the sugary run-off.

Now I personally batch sparge because it's faster and easier. But guess which method extracts more sugar from the mash? Yup, it's the fly sparging. (That's why all commercial beer makers fly sparge; they have to maximize their yield of fermentable sugar from a given measure of malt.) The reason is that water can only hold so much sugar in solution and so adding the water gradually and continuously allows the sparge water to extract the maximum amount of sugar from the mash.

Obviously, the same principles are at work in coffee making. The French press makes a wonderful, rich, flavorful cup of coffee, but the single infusion of water can only take up so much extract from the coffee grounds. Just as in beer making, a slow, continuous stream of hot water extracts much more from the same volume of coffee.

Now that all may have been immediately obvious to everybody but me. Still, it was fun to think it all through. Another of life's little mysteries solved. Now if only beer making could help me understand how a neatly coiled rope can get knotted in fifty seven places just by being laid on the ground.........


The Guild Master said...

That's interesting and useful information. I currently batch sparge and obtain pretty good yields, but the knowledge that I could do better is going to bug me now!

ThePalmHQ said...

I hear you, GM, but you do have to factor in what your time is worth. I personally would not be brewing from all-grain at all if it were not for Denny Conn's "Cheap 'n Easy Batch Sparging Method" (referenced via link in the posting above.) Having to add a pound or two of extra grain is a small price to pay to be able to brew from all grain. So I choose to invoke one of my favorite sayings: Don't let the best become the enemy of the good.

Thanks for commenting.

The Guild Master said...

Hi TPHQ, I agree, time does become a factor. I've been doing all-grain mashes for around 5 years now and for most of that time I've been too precious about getting the wort to run bright during sparging. A year ago I was chatting to an old hand who said not to get too up tight about it. I followed his advice and just pushed through the sparge. Was clarity an issue in the final product? No - there was no noticeable difference. Did I save hours during my brew day? You bet. Was I happy? Ditto!

C.F. Mathews said...

All I know is that french-pressed coffee tastes good. I've heard that it may be less healthy due to more oil exposure which can possibly increase your cholesterol.

Cassandra said...

No that still doesn't explain it.

You ask why a French press requires twice as much coffee to reach the same strengh. And then say that water can only hold so much in solution.

If the issue were how much a volume of water could hold in solution, then there would be no difference in actual strength in a cup of coffee regardless of how produced. A drip coffee maker may drip more water over the coffee and extract more, but that should still leave it at the same concentration.