WEB EXCLUSIVE: Perfectly Timed French Press Coffee

I've seen it. You've seen it. We all have. That little piece of paper with printed instruction on how to use a French press. 

You know - the one that says: "Take the included scoop and dump "X" scoops in the press per cup of water, pour in the heated water, let coffee sit for four minutes, and then press and pour."  

The box promises that you will be rewarded with such a great cup of coffee that you will make never again want to go back to drinking drip coffee from a machine.

Yet time and time again I hear people that I meet say "Yes, I have tried a press but every time I use the press the coffee it makes tastes awful."

One reason for this is that none of the instructions that come with a press suggest how to adjust the process for different amounts of coffee being brewed. One could conclude that no matter the amount being brewed, four minutes is the correct time to press. 

All other factors being consistent, the instructions suggest that coffee from an 8-oz press should taste the same as that from a 24-oz press after four minutes. Here at Old Wwworld Cafe we decided to challenge this standard and the results are surprising.

The idea was simple. We set up one, two, and three cups presses (8 oz water to 16 grams of coffee) and brewed them at 30 second intervals, starting at 30 seconds and going up to four minutes. After four minutes, if the flavor had peaked, we increased the time to try to see if there would be a drastic change in acidity or opacity. Many people have commented on how acidic a long sitting press could taste. So, surely, an eight minute press would register far more acidity than a two minute extraction. With that in mind, we began to brew. 

ONE CUP (8 oz.) Coffee Press Extraction
.5 minutes	1 minute	1.5 minutes	2 minutes	2.5 minutes	3 minutes
Eight ounces of water at 200 degrees is poured into a 32 oz press with 8 grams of coffee per 4 oz water.
	3.5 minutes	4 minutes	4.5 minutes	5 minutes	8 minutes

Each cup series underwent the same process. We measured 8 grams of coffee and put it in the grinder. Then we boiled the water. In the meantime, an instant read thermometer and pH meter were readied. When the water came to a boil the grinder was turned on. The water was reheated to maintain 200 degrees for the pour. Next, the grounds were funneled into the press. A precise amount of water was measured and slowly poured on top of the grounds.The grounds were stirred twice (with a wooden spoon to be non-reactive). The timer was started the moment water and grounds came into contact.

TWO CUPS (16 oz) Coffee Press Extraction
.5 minutes	1 minute	1.5 minutes	2 minutes	2.5 minutes	3 minutes
Sixteen ounces of water at 200 degrees is poured into a 32 oz press with 8 grams of coffee per 4 oz water.
	3.5 minutes	4 minutes	4.5 minutes	5 minutes	8 minutes

Plunging a press after 30 seconds proved to be a challenge and speedy hands were a must. The coffee from each series was poured evenly into three separate cups. To eliminate any mud in the cup the coffee in the cup that was used to test opacity was run through a paper filter. The second test cup was measured for pH and temperature, and the last cup of coffee in each series was for tasting. After it was tasted the lights were turned off and a solid white light placed above the cup used to measure opacity. Pictures were taken, our notes recorded, and the process was repeated. 

After brewing 31 cups, the results were a bit of a surprise. The most noteworthy difference is in the taste.  As we expected, volume does in fact require a change brewing time when using a press. Although further research is needed to determine why, our thought is that this has to do with variations in the surface area of the coffee in the press. We believe that a trough would extract the same amount of coffee flavor faster.  

Here are the results 

In our opinion, a single cup of coffee should be brewed in a French press for no longer than two minutes, and the flavor was never quite as good as that made in a two or three cup press.. Two cups should be brewed between 2.5 to 3 minutes, and three cups should be brewed 3.5 to 4 minutes.

The last noteworthy results were acidity and color came through on a cup almost instantly.  A press that sat for eight minutes, regardless of volume, had almost the same acidity as a press that sat for 30 seconds  The extraction rate of the organic compounds and the sugars to a lesser extent seems to be the surface area of the coffee that is exposed to circulating water as it brews.  The color in coffee is similar to dye. It should not come as a shock that most,  but not all color, is easily attained from grounds.

Experimental Details:

Costa Rica Coffee (allowed to rest 6-48 hours after roasting before being used in the experiment)

Equipment: 

Mazzer Major  Parallel Burr Grinder	Bodum Double Wall Columbian (32 oz)
Three 12 ounce cups	Filter basket and filter paper
Kitchen scale sensitive to one gram	Electronic pH meter
White light LED flash light	Electronic thermometer
Wooden Spoon (for stirring)	Gold Cup Standard Water
Timer	Electric Kettle

Result: Hypothesis was proven correct as the volume of coffee brewed increases so should the time that the solution is allowed to brew.   The effect does not seem to be from the acidity or the color contributing compounds but  the organic compounds (good and bad)  and sugars.  Flavor profiles show that ionic acid compounds are the first to be extracted by the polar water followed by the sugars, volatile flavor compounds, and finally the bitter organic oils and compounds. 

The extraction of the organic compounds and the sugars to a lesser extent seems to be the surface area of the coffee that is exposed to circulating water as it brews.  During the brew most of the coffee will float at the top or sink to the bottom of the French press.  This has less of an impact on a one cup French press due to the relatively low volume of water and coffee.  The coffee has the ability spread out on the surface of the water in a thinner layer of grinds as opposed to a three cup French press in the same container. The layer formed would be three times as thick allowing less water to circulate through the coffee grounds.

Daniel Drazenovich was the Chemical Engineer involved in this experiment. He is Chief Technical Engineer at the company. Ashley Hudek aided in brewing and shot the photographs. Learn more about the experimenters by visiting www.theoldworldcafe.com/index.php