The Relationship Between Coffee Strength and Caffeine

crazy by Editorial Staff | Updated on February 23rd, 2023

Some days are worse than others, and on these days, we want our coffee extra strong. But do we really know what strong coffee means? And does strong coffee have more caffeine?


What you need on days that are heavier than usual is a jolt of caffeine, but upping your coffee’s strength doesn’t necessarily provide that. The chemical composition of a coffee does not dictate its strength.

four coffee cups on floor

It’s actually the physical properties that do. Scientists are interested in “total dissolved solids” measures expressed in percentages.

Total dissolved solids

Giulia Angeloni, an agricultural researcher at the University of Florence in Italy, said, “Total dissolved solids means the number of substances present in the coffee compared to the water itself that composes it.”

In other words, the more coffee there is than there is water, the more dense, bold, and intense your cup of Joe is. 

Brew method that has the most caffeine

Angeloni, together with her research team, brewed coffee in eight different ways and studied its physical and chemical properties. Their findings, which are published in Food Research International, broke down which brew gave out the strongest coffee and which method gave the highest caffeine content.

On top of three different methods of espresso brewing, they also utilized French press, pour-over, AeroPress, cold brew, and Moka pot coffee. “We have demonstrated the importance of extraction conditions, comparing the different methods with the same coffee,” Angeeloni stated. 

Caffeine and strength

The researchers utilized the concentration of caffeine to calculate the estimated caffeine per serving. The caffeine-per-cup is estimated based on the smaller European cups in comparison with the North American ones.

In the graph below, the caffeine concentrations derived were multiplied by the typical North American cup sizes to come up with this caffeine per serving information. 

This graph from Bean Poet shows the six brewing methods. The X-axis houses the caffeine per serving, while the vertical Y-axis shows the total dissolved solid or what we call the “strength.” 

Graph’s four quadrants

  • Gentle: Low total dissolved solids and low caffeine content. The closer to the bottom left, the milder the coffee.
  • Aggressive: High total dissolved solids and high caffeine content. The closer to the top right, the more tasty and strong the coffee is.
  • Showy: High total dissolved solids and low caffeine content. Coffee tastes bold and big, but it may not keep you awake when you need to/
  • Sneaky: Low total dissolved solids and high caffeine content. This coffee may not pack all the taste in the world, but don’t be deceived! This will keep your eyes wide open all night.

Espresso

It turned out the espresso didn’t even set foot into the “aggressive” category. It’s undeniably stronger than other coffee brews, but since the serving is small per espresso shot, it wasn’t able to make it to the top right quadrant. If only the testing was based on the caffeine concentration, this story would be different.

Moka pot

Coffee from the Moka pot stands in the middle when it comes to the strength scale. But, like the espresso, it didn’t make it further because it was served in small doses. 

Aeropress

Brewing with Aeropress means the amount you can brew at a time is limited. The research team cooked up 7 ¼ ounces in a single brew, so we depended on that for the serving size.

With that, the Aeropress fell into the gentle corner. Take note that the researchers steeped the Aeropress for a minute. Should it be longer, the additional extraction may change the narrative.

French press

It’s a no-brainer that French Press is a gentle coffee, probably one of the most among all the tested brews. It houses the lowest total dissolved solids percentage.

Although its caffeine per serving is higher than the Aeropress, this is due to it being served in a much bigger cup. The steeping time utilized for this is five minutes.

Hario V60

Hario V60 is usually served in cup sizes like that of French Press coffees. It was calculated to be a standard 12-ounce cup. Despite that, it has more caffeine.

The researchers soaked the beans as they were allowed to bloom. They were then saturated with a slow pour of three minutes. The brew that resulted is one that isn’t very strong but with a significant amount of caffeine kick. 

Cold brew

We know that cold brew is a highly concentrated cup of coffee that is typically diluted with water. Because of this, the brew was found to have relatively low total dissolved solids.

This may also be owed to the short brew time of just five hours. Coffee experts recommend an overnight brew or 12 to 14 hours at the very least. This comes in an eight-ounce serving size to give room for dilution.

Brewing details

The same commercial brand of mineral water and the same pure Arabica beans from Gera Estate in Ethiopia were used across all brewing types done in the research. However, other variables were dictated based on the brew type, such as the grind size, brewing temperature, equipment used, and the coffee-to-water ratio.

Other chemical compounds

The concentration of chlorogenic acids was also taken into account by the researchers. “Chlorogenic acids are the major source of polyphenols in coffee, and they are one of the major strong antioxidant compounds in coffee,” said Angeloni.

“They can neutralize free radicals, reducing their harmful impact on the body and substantially slowing down their destructive processes. In addition, chlorogenic acids attend directly in some important metabolic processes of the human body.”

The research revealed that CGA concentration is associated with caffeine concentration.

How much coffee?

The U.S. Food and Drug Administration recommends a safe 400-milligram dose per day. Based on the study, a couple of 12-ounce French press coffees will keep you within the safe dose, while the two 12-ounce pour-over coffees may be too much.

Diluting your 8-ounce cold brew to have a 12-ounce cup will put you in the safe zone. 

Now there you have it! We hope we have shed some light on the difference between coffee strength and caffeine content.

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Editorial Staff

The editorial staff at Crazy Coffee Crave is a team of coffee enthusiasts & Baristas who enjoy the one thing we all think about as soon as we get up in the morning. Trusted by thousands of readers worldwide.