Plunger, espresso, filter? Just because your coffee is bitter doesn’t mean it’s “stronger”

Coffee – a bean with many possibilities. A big choice is how to prepare it: espresso, filter, plunger, percolator, instant and more. Each method has unique equipment, timing, temperature, pressure, coffee grind, and water requirements.

Our choices of brewing method can be cultural, social or practical. But what impact do they really have on what’s in your cup?

What is the strongest drink?

It depends. If we focus on caffeine concentration, on a milligram per milliliter (mg/ml) basis, espresso methods are generally the most concentrated, capable of delivering up to 4.2 mg/ml. This is around three times higher than other methods like the Moka pot (a type of boiling percolator) and cold brew at around 1.25mg/ml. Drip and plunger methods (including French and Aero-press) again account for about half of that.

Espresso methods extract the most caffeine for several reasons. Using the finest grind means there is more contact between the coffee and the water. Espresso also uses pressure, pushing more compounds into the water. While other methods brew longer, it doesn’t impact the caffeine. This is because caffeine is water soluble and easy to extract, so it is released at the start of the infusion.

But these comparisons are made on the basis of extraction non-typical situations consumption situations.

So while espresso gives you the most concentrated product, this one comes in a smaller volume (only 18-30ml), compared to much larger volumes for most other methods. These volumes vary depending on the manufacturer of course, but a recent Italian study set a typical filter, percolator and cold brew end-use at 120ml.

Based on these calculations, cold brew is actually the highest dose of caffeine per serving at almost 150mg – even more than the 42-122mg totals found in finished espresso. Although cold brew uses cold water and a larger grind size, it is brewed with a high coffee to water ratio, with extra beans needed in the brew. Of course, “standard services” are not a reality; you can multiply the portions and oversize any coffee drink!

With the price of coffee rising, you might also be interested in extraction efficiency – how much caffeine you get from each gram of coffee.

Interestingly, most of the methods are actually quite similar. Espresso methods vary but average 10.5 milligrams per gram (mg/g), compared to 9.7 to 10.2 mg/g for most other methods. The only outlier is the French press, with only 6.9 mg/g of caffeine.

The French press or coffee plunger was actually invented in Italy, despite its modern name.
Rachel Brenner/Unsplash

“Strength” is more than caffeine

The caffeine content explains only a small part of the strength of coffee. Thousands of compounds are extracted, contributing to aroma, flavor and function. Each has its own extraction pattern, and they can interact with each other to inhibit or enhance the effects.

The oils responsible for crema – the rich brown “foam” on top of the brew – are also extracted more easily with high temperatures, pressures and fine grinds (another potential gain for espresso and Mocha) . These methods also yield higher levels of dissolved solids, which means a less watery consistency – but, again, it all depends on how the final product is served and diluted.

To complicate matters further, the receptors that detect caffeine and other bitter compounds are highly variable from individual to individual due to genetics and training to our usual exposures. This means that the same coffee samples could invoke different perceptions of their bitterness and strength in different people.

There are also differences in our sensitivity to the stimulating effects of caffeine. So what we look for in a cup, and what we get out of it, depends on our own unique biology.

A multi-faceted aluminum pot with a black handle, with steam coming from the spout
The Moka pot, another iconic Italian invention, brews coffee at high temperatures on a stovetop.

Is there a healthier brew?

Depending on the title or the day, coffee can be presented as a healthy or unhealthy choice. This is partly due to our optimism bias (of course we want coffee to be good for us!) but may also be due to the difficulty of studying products like coffee, where it is difficult to grasp the complexity of brewing methods and other variables.

Some studies have suggested that the health effects of coffee are specific to the type of brew. For example, drip coffee has been associated with more positive cardiovascular outcomes in older adults.

This link could be coincidental, based on other coexisting habits, but there is evidence that filter coffee is healthier because more diterpenes (a chemical found in coffee that may be linked to increased levels bad cholesterol) are left in the coffee and the filter, which means less going to the cup.

The bottom line?

Each brewing method has its own characteristics and inputs. This gives each a unique profile of flavor, texture, appearance, and bioactive compounds. While the complexity is real and interesting, ultimately how to brew is a personal choice.

Different information and situations will cause different choices in different people and on different days. Not all food and drink choices need to be optimized!

Read more: A dark brew: Coffee, COVID and colonialism have left millions struggling to make a living

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