Coffee Grind Time and Caffeine: Is There a Connection?

Coffee Grind Time and Caffeine: Is There a Connection? New Research Says Yes!

Or Alternate Title “42: The secret to life, the universe and a strong cuppa” HT: Douglas Adams

By  Michelle Z. Donahue

Coffee Grind Time and Caffeine
Researchers Christopher Murray and Thamara Laredo in their lab at Lakehead University. (Photo credit: Christopher Murray)

If you’ve ever wondered how long you should be grinding whole coffee beans to get the max amount of caffeine in your morning joe, you now have the ultimate answer.

Inspired by a former co-worker who used to grind his beans for what seemed like a œridiculous amount of time,  Christopher Murray and Thamara Laredo decided to settle the question once and for all: how long do you need to grind to get a good, strong cup of coffee?

Murray and Laredo, both researchers in the Department of Sustainability Sciences at Lakehead University in Orillia, Canada, recently looked into this very question and came up with 42 seconds. That’s the magic number to get the strongest cup possible out of even a relatively small volume of beans.

œPeople would shake their heads, listening to him grinding,  Murray said of his former colleague, laughing. œHis intention was to make the coffee so strong the spoon would stand up in it. I didn’t know if he was crazy or not, but I wanted to see if there was anything to it. 

Grind Time and Caffeine
Coffee in the blade grinder ready for the author to do some SCIENCE!

For their experiments, Murray and Laredo used electric blade grinders, primarily because of cost: they figured that more people probably have blade grinders simply because they’re less expensive than burr grinders. Working in time increments from zero (whole beans) to a whopping 84 seconds of grind time, they ran about five tablespoons of samples through a Black and Decker percolator then analyzed the extracted caffeine in a spectrophotometer. They also compared their results against decaffeinated beans, which matched up with whole, unground beans.

Coffee Grind Time and Caffeine
And the same coffee after grinding. (My husband counted to 25 before he gave up this morning, and the grinder was sounding sort of grumpy at that point anyway.)

Grind experiments have been conducted before, but hadn’t explored a full range of possible grinding times to see exactly how much caffeine gets dumped into a 12-cup pot of coffee. The standard time recommendation for grinding beans is 10 seconds. But when Murray and Laredo added another 30 seconds, what they found surprised them: the caffeine content increased by 100 percent.

Coffee Grind Time and Caffeine
Caffeine content peaked after 42 seconds of grind time and decreased thereafter.

œYou would expect that it is more, that you’d get more caffeine the finer you grind, but to get twice as much, that was kind of surprising,  Laredo said. œBut you have to go a long time ”I don’t think people in their right mind usually go that far. 

Try it, and you’ll quickly see what she means: stand in the kitchen with the little grinder buzzing for more than half a minute, and even 20 seconds begins to feel just silly.

To make sure it wasn’t a function of how long the water took to pass over the grounds, the two researchers tested the caffeine content of coffee that took five minutes to brew and compared it with coffee that was left to stand with grounds for 20 hours. The caffeine content didn’t change, so they concluded that the increased caffeine could only be accounted for by the size of the coffee grounds themselves. The finer the grind, the higher the level of caffeine, no matter how long it took for the coffee to brew, or even how much water the grounds themselves absorbed.

Interestingly, any additional grinding after 42 seconds didn’t increase the caffeine content, though Murray warned that grinders tend to get a little hot after such an extended milling session. Plus, there’s the awkward sensation of just standing there for so long.

œThere’s a limit to how long you can press that button before you start to feel insane,  Laredo added.

And if you don’t feel like counting to 42 every morning just to annoy your office mates, you’ll probably get close to the full effect if you settle for grinding your beans for a mere 30 seconds.

Plus, you’ll make a bag of coffee last that much longer.

The results of the study were published in the February 2015 issue of the Journal of Food Research.


Michelle Z. Donahue  is a  journalist and freelance writer  who often writes on quirky science and the natural world. A graduate of Vanderbilt University, Michelle lives in Maryland with her husband and two children, who do their part to help harvest green beans from the garden in summer. One of her favorite DIY experiments was roasting green coffee beans in a hot air popcorn maker, which made the yard smell an awful lot like the German  konditorei  of her youth.

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  1. Interesting idea for an article…. But here’s the thing:

    The amount of time it takes to grind coffee does not have as much of an impact on the strength of your coffee as much as how finely ground your coffee is.

    I think it’s important to point out that this study ONLY applies to BLADE grinders, which most people who take coffee seriously can agree should be avoided. While I say that, I also acknowledge that blade grinders are an economical choice for home coffee drinkers. I’m not 100% against blade grinders, I just think burr grinders are way better, and more and more quality affordable burr grinders are becoming readily available.

    Using a BURR grinder, you can achieve the same fineness of grind as you did with the blade grinder in the study, and it wouldn’t take nearly as long. It might take 20 seconds at most if your using a typical home burr grinder like a Baratza Encore.

    The time it takes to grind is a variable that doesn’t really need to be considered for most consumers.

    The only instance where I worry about time is when it is taking too long to grind in a burr grinder. The longer the grinder is turned on with the burrs spinning, the more friction that’s created, and the more heat that is created. When your coffee grounds get heated in the grinder it has a negative effect in the cup.

    My point is that extraction ( strength) is (mostly) determined by grind size (fineness) and not the time it takes to grind.


  2. We were wondering about this for a really long time. Thanks for the article, we shared it on our social media feed. Keep up the good work, you guys a great source of espresso news for us.

    All the best from everybody here at

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