I have a grinding machine with a lot of different settings. Even between the categories of Fine and Medium there are sub levels of grinding. I'm not sure how they relate to the flavor of the coffee. Is there any research that shows how the grind affects the taste of the different types of roasts?

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  • What coffee grinder is that? Answers might be more specific if you give us that information – Anthony Pham Jan 28 '15 at 1:29
  • @PythonMaster, it looks like a Capresso Infinity from the listings I found of products for sale. – TheFontSnob Jan 28 '15 at 2:45

The main reason for different grinds is the different brewing processes. If the water is exposed to the grounds for a very short amount of time (e.g., 10-15 seconds for espresso), you need a finer grind to provide enough surface area to extract the coffee from the beans. If the brewing time is long (e.g., the ~4 minutes of french press), you need a coarse grind to avoid over-extracting the grounds and getting something too bitter to drink.

That's really the heart of it. If the grind is too coarse for your brewing method, your coffee will end up under-extracted, weak, and acidic. If it is too fine a grind, your coffee ends up over-extracted and bitter. Your grinder is a good brand; if you still have the manual, it includes a guide to grind vs. brewing method. If not, the capresso.com site includes PDF versions.

  • +1 For the info! So it will depend on the time used to make coffee? – Anthony Pham Jan 28 '15 at 1:25
  • That's the rule of thumb, yes. I realized after posting my answer that I hadn't addressed your question about roasts, but that's because each roast is more of a "constant," stable within themselves, while grind and brewing method are where the drinker has control. – TheFontSnob Jan 28 '15 at 2:44

In your title, you mention grind consistency. This is different from but related to grind size - an inconsistent grind (such as a whirling-blade type "grinder") will have sizes all over the map, from dust to half a bean. The dust will be over-extracted, and the half-a-bean won't contribute much flavor at all.

A consistent grind (one with particles in a small range of sizes, neither excessively large nor excessively small) makes it more feasible to get the contribution of all the coffee grounds to the beverage without over-extracting any of the grounds - thus making it possible to get a more consistently predicable cup of coffee, without off flavors from some part of the grounds and no flavor from another part.

Having fine control over the grind size in a consistent grinder makes it possible to adjust the grind to produce the best cup (to your taste) in the equipment you have for brewing.

It's already been stated that grind size will change depending on your brewing method.

Here is a quick break down of which grind size aligns with what brew type(the most popular ones).

Keep in mind everybody's taste is different, You may have to make small adjustments to find yours.

  • Coarse - French press , Cold Brew

  • Medium to Medium/fine - Manual drip, Automatic drip

  • Fine - Espresso, Turkish

You might find this resource helpful.

Happy Coffee!

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