Tag: scientific

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brewing coffee news

Brewing Coffee with Ultrasound

coffee in a hario can on a scale

A site called LabDownUnder has a blog about research from Australia that explores using ultrasound to brew coffee. In other words, the high-pitched sound waves used in medical imaging can also make a cup of coffee!

They wanted to see if ultrasound could change how much of the good substances (such as caffeine, oils, and flavors) gets extracted from the coffee grounds.

Coffee Sonication

To test this, they brewed filter coffee with and without ultrasound, changing things such as how much coffee they used, the water temperature, and how long they used the ultrasound. They then measured the concentrations or quantities of antioxidants, caffeine or oils, and the specific smells and flavors in the brewed coffee. They also judged what the coffee looked like – its color and how much foam it made.

Ultrasound can be used to extract important compounds in the brewing process through what is known as cavitation. As the sound waves travel through the water surrounding the grounds, differences in pressure create microscopic bubbles which themselves expand and collapse.

LabDownUnder

The Findings

They found that ultrasound helped get more caffeine and oils out of the coffee grounds. This is probably because the ultrasound waves shake things up at ultra fast rates, making it easier for the compounds in coffee to dissolve into the water. They also found that ultrasound helped extract more of the compounds that give coffee its aroma, which means the coffee might smell even better!

However, they noticed that ultrasound seemed to decrease the amount of antioxidants in the coffee, especially when they used it for longer or at higher temperatures. Also, the coffee brewed with ultrasound had a lighter color and less foam, which they think is because of the extra oils. These oils are called triglycerides.

While traditionally the crema floats on top of the coffee, ultrasound actually emulsifies the triglycerides (oils) that make up the crema layer with the beverage, mixing them together. This created a milky-looking beverage with caramel tones.

The Results

Overall, the research suggests that using ultrasound to brew coffee could be a way to make coffee with more caffeine, a richer flavor, and a stronger aroma. However, it might also have less antioxidants and a slightly different appearance. More research is needed to fully understand the potential of ultrasound in coffee brewing.

Dr Francisco Trujillo of the School of Chemical Engineering of UNSW was chief investigator behind the study. The original article has a link to a video made by the researchers, that I cannot link to without permissions. They also show a photo with a color comparison between French press and sonicated coffee. The sonicated coffee looks like it already has milk added to it, when it doesn’t! Check the link to the blog at the top.

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brewing coffee news

The math of brewing a better espresso

espresso doppio

Scientists have finally answered a burning question of mine: why should an espresso be brewed in 25 +/- 2 seconds and use approx 15-22gr of dry coffee to yield 50ml of (a double) espresso?

Who came up with this rule and why? Not that I have a specific problem with it but it seems so arbitrary. Also, once you start to make espresso’s a day long, you’ll notice that it’s really hard to dial in the equipment a certain way and maintain those rules for every cup. Sometimes it’ll be 21 seconds, sometimes 29. The grinder is pretty accurate. The beans are practically the same. So where does this high variation come from?

Well, it turns out that brewing your espresso differently yields the same great taste and flavors while achieving this with much greater consistency and reducing the cost per cup of espresso!

How did they do it? Well, they started by reducing the process to a proper model with solid mathematics behind it. Brewing an espresso is basically fluid dynamics of a bed of particles. The “puck” being coffee grinds of varying sizes and water is pushed through this bed at a certain pressure.

These mathematics are very well understood and accepted. So the scientists started with this model, created equations for everything and solved the equations using differential equations. That resulted in a few parameters and then they found the optimal solutions.

Sounds easy enough but believe me the math is pretty impressive, yet their logic is sound.

Turns out if you lower the pressure to 6 bars instead of 9, use 7-15gr of dry coffee, ground more coarse then tradition tells you to and aim for an extraction of 8-15 seconds, you will get a beautiful espresso that is much easier to reproduce!

Don’t believe it? Read the articles: