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There are two types of mechanical grinders for coffee: blade and burr. Blade grinders spin at high speed, chopping the beans into grounds, while burr grinders move the beans between burrs, which crush them.

The claim is that burr grinders produce a superior cup of coffee. "Blind" cuppings are common in the world of coffee: have these established that the taste of coffee is affected by the grinding mechanism?

The claim is made at, for instance, How Stuff Compare:

Many coffee aficionados consider coffee made from a burr grinder to be superior to that made from a blade grinder because the essential aromas and oils of the coffee are preserved since the grounds are not overheated. The superior consistency of the grounds also makes for a better flavored, less bitter brew because the flavor is more evenly extracted from the grounds.

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    I'll be satisfied when it can be proven they taste different and maybe why – ratchet freak Oct 17 '11 at 19:08
  • Agreed with @ratchet -- my question is whether the tastes are detectably different in blind taste-tests; the subjective aspect is clearly OT. – Larry OBrien Oct 17 '11 at 19:31
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    I don't know of any scientific research, but from personal experience I can tell you that it largely depends on the brewing method you are talking about. I don't think I would be able to tell the difference between both grinding methods on filtered coffees, but I definitely would on french pressed examples. – user5773 Jan 17 '12 at 3:50
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    And just to explain a little further, a blade grind can be very inconsistent, and on a french press the smaller particles can pass through the mesh, while ideally the grind should be consistently coarse, so that wouldn't happen. – user5773 Jan 17 '12 at 3:54
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    I really don't see how a blade grinder can make a consistent grind since the blades pass through the beans multiple times so some will be "sliced" more than others, while in a burr grinder, the coffee makes one pass through the burrs that are set an appropriate distance apart. I'd be surprised if 10 seconds in a blade grinder causes enough frictional heating of beans that were roasted at 400F+ degrees to affect the flavor a few seconds before they are plunged into 200F degree water. – Johnny May 10 '13 at 21:57
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Yes, it would taste different. Comparing "better" or not is irrelevant, since the question asks simply if it is "different." Here is why it's different:

What is the difference between blade- and burr-ground coffee? Consistency/uniformity of the grind.

It is made up of two revolving abrasive surfaces (called burrs), in between which the coffee is ground, a few beans at a time. ... The reason that coffee aficionados tend to choose burr grinders over blade is that the beans are ground in a uniform size, and you have more control over your grind than you do with a blade.

What is the difference between a burr and blade coffee grinders?

There is also the claim that using a blade grinder, with the blades whirring at high speeds, coming into contact with the beans and grinds, causes heat from the friction of contact, altering the flavor. Not sure how true that claim is, though.

How to Grind Coffee - Learn About Coffee Grinding

Do different levels of grinds lead to different tasting coffee?

When it comes to grind size, there are three factors which make the biggest difference: contact time, extraction rate and flow rate. To put it simply:

The extraction rate of coffee grounds increases with a larger surface area.

  • To increase surface area, grind the coffee finer.
  • The higher the extraction rate, the less contact time is needed.
  • A finer grind can reduce the flow rate of water, increasing the contact time.

Knowing this, if you have a brew method with a short contact time, the grind should be finer. In an immersion brewer, which steeps coffee grounds in water for several minutes, the contact time is much higher and, thus, requires a more coarse grind than most other brew methods.

If the contact time is too high or the grind is too fine, it will result in an over-extracted brew which can be bitter. If the grind is too coarse or the contact time is too short, the coffee will turn out weak.

Coffee grind size: Why it matters and what you should be using

They certainly do. A finer grind exposes more of the grounds to the water, releasing more oils, and flavor components, both good and bad (depending on what you like). A finer grind will be stronger flavored, but also more bitter, for instance. Depending on filtration method, it can also lead to more or less particles of the coffee grinds winding up in your cup. If the size of the grind didn't matter, you wouldn't have distinct types of coffee calling for specific grind sizes.

So, we've established that a blade grinder will lead to more variability in the final size of the coffee grounds, and we've established that different levels of grind size do lead to different flavors and consistency, even when starting with the same beans. By definition, a coffee with more uniform ground size is going to have a different taste than one with a variable grind size.

EDIT: Contrary to my assumption, this matter is not too trivial for actual scientific study. There was a study in the Journal of the Science of Food and Agriculture that looked at extraction variables as they apply, specifically, to espresso served in coffee shops, but there's nothing about this that makes it exclusive to espresso. They note that consistency of grind and standardization as the #1 factor affecting the outcome or taste. Thanks to OddThinking for pushing me for more verification of this. -

From the abstract:

...The major source of information was contained in the grinding grade, which accounted for 87% to 96% of the variance of experimental data....

CONCLUSION: The variability in volume and chemical attributes of EC (espresso coffee) is large. Grinding had the most important effect as the variability in particle size distribution observed for each grinding level had a profound effect on the quality of EC. Standardization of grinding would be of crucial importance for obtaining all espresso qualities with a high quality.

How the variance of some extraction variables may affect the quality of espresso coffees served in coffee shops

  • Is this not an answer based purely on a theoretical model? It would be gazumped by a simple experimental result. (I think I am being triggered particular by the phrase "By definition", which seems to mean in context "According to my model"!) I guess it boils down to why I should believe the bolded quote is correct, and not just a repeat of the claim. (Note: I do not drink coffee, so somethings that may seem obvious to you through experience aren't to me, sorry.) – Oddthinking Mar 23 '17 at 2:08
  • @Oddthinking - no it is not theoretical. We understand, empirically and scientifically, the mechanism by which flavors and physical substances are extracted from ground beans when mixed with water, cold or hot, are filtered, and are put into a water-based suspension solution. We know that the level of grind and surface exposure affects this. Since the surface exposure and time of exposure is a proven factor, BY DEFINITION, altering this alters the outcome. What would be theoretical and fuzzy would be doing an experiment where we ask people if they think something tastes different. – PoloHoleSet Mar 23 '17 at 13:16
  • @Oddthinking - this understanding is not limited to just coffee, but is something that has been observed and understood across a variety of substances and solutions. I didn't link to any specific scientific studies because my assumption was that this would not be worthy of a controlled study. Looks like I was wrong, and there is one, specific to caffeine infusion, but hopefully we can extrapolate that it carries over to general extraction of substances in the ground beans. – PoloHoleSet Mar 23 '17 at 13:26
  • Skipped the caffeine infusion one and found another more applicable. – PoloHoleSet Mar 23 '17 at 13:43
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I could not find any academic studies on this topic, but there is a good discussion of grinders in November 1, 2001 issue of Cook's Illustrated. Cook's Illustrated is not science, but they do provide empirically-based and often experimentally-informed opinions (in contrast with other cooking / kitchen equipment review outfits).

According to Cook's:

The burr grinders produced a more even grind, but tasters didn’t find that more evenly ground coffee translated into improved flavor.

Tasters did prefer the rich body of burr-ground coffee, but they also noticed the tendency of this coffee to taste slightly bitter, owing in part, no doubt, to the more fine and even grind, which made for the coffee’s greater exposure to and prolonged contact with the water in the coffee maker.

We were surprised to discover that the coffee brewed with blade-ground beans was less likely to turn out bitter. The tasters did note that coffee from blade-ground beans had less body than coffee from burr-ground beans, but we were happy to sacrifice a little body for the reduced risk of brewing bitter coffee.1

But, as John Manzo reminds us in "Coffee, Connoisseurship, and an Ethnomethodologically-Informed Sociology of Taste" (Hum Stud, 2010 33:141–155):

‘‘taste’’ evinced by the coffee geek is ‘‘social,’’ [...] it is shared, understood, delineated, defined, made sense of, and generally appreciated as and oriented to as an aspect of the social groups and networks that constitute the subculture itself.2

In other words, buying expensive burr grinders and talking about them online or with your friends will help you get "props" from fellow coffee geeks. The coffee may even taste better to you, because taste is not wholly objective, and is, in part, a socially-constructed thing.

  1. http://web.archive.org/web/20141106005055/http://www.cooksillustrated.com/equipment_reviews/638-coffee-grinders

  2. http://web.archive.org/web/20150525142748/http://link.springer.com/article/10.1007/s10746-010-9159-4

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    The Cook's article tested using an "automatic drip machine" and they don't detail the methodology of their taste testing. It would be interesting to see a double blind test done with the pour over brew method. – Code Commander Mar 13 '14 at 3:02
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    @CodeCommander Agreed, but I don't think such a study exists yet. The Cook's article has other problems too: burr grinders allow the brewer to set the exact grind size, which invalidates the whole line of reasoning about "too fine of a grind" vs. blade grinders. In fact, consistency at range of granule sizes is one one of their main advantages. This is why you don't see many blade grinders for commercial applications (like coffee shops, where consistency is important). – denten Dec 20 '14 at 23:09

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protected by Oddthinking Jan 17 '12 at 7:31

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