Beautiful, rich, and exceedingly bitter espresso - Page 2

Beginner and pro baristas share tips and tricks for making espresso.
fizguy

#11: Post by fizguy »

another_jim wrote:You are misreading my post and quoting the wrong section. For a normally flowing shot, extraction is determined by grind setting, nothing else. The order of extraction is as follows:

<image>
Jim, I think I need help understanding. The graph shows extraction time as the independent variable which is in direct conflict to the statement that grind is the determining factor. Can you clarify for me?

User avatar
another_jim
Team HB

#12: Post by another_jim »

The finer the grind, the less time it takes. The graph shows the order of extraction; with the caramels extracting last. If the shot is such that acids or bitters overbalance the sweetness, you can grind finer and extract more caramels to compensate (if the coffee is roasted very dark, much of the caramel will be more bitter than sweet, and grinding finer won't help; but if the coffee is so dark, it's pointless working with it in the first place).

The slide is from a talk I gave recently; it might help clarify what I'm trying to say.
Jim Schulman

Cerini Coffee & Gifts: official US importer for Olympia Express
Sponsored by Cerini Coffee & Gifts
User avatar
mariobarba

#13: Post by mariobarba »

I am not Jim and I do not have anywhere near his expertise but I do teach science (not sure how much of a qualification that is) and so here is my attempt to clarify. In the graphic Jim provided, extraction time is indeed the independent variable and the extraction percentage is the dependent variable. In the case of this graphic, grind fineness is not a variable. If one were to describe a relationship between grind fineness and extraction time, then fineness would be the independent variable and extraction time would be the dependant variable. So really, fineness is the ultimate independent variable with the other two variables ultimately depending on that.

Think of it this way, the finer you grind the longer the extraction. The longer the extraction, the higher the percentage of caramels will be.

So to recap, extraction percentage (flavour profile) depends on extraction time, which depends on grind fineness.

I'm sure Jim will chime in with a more eloquent explanation, but until that happens I hope this helps.

(as an aside, I wonder how temperature interacts with extraction percentage and how it affects the relationships between time and percentage?)

User avatar
mariobarba

#14: Post by mariobarba »

Imagine my response up one post, Jim must have beat me by seconds.

fizguy

#15: Post by fizguy »

Except you said "the finer you grind the longer it takes," and Jim said, "the finer you grind the less time it takes."

Jim, would it be fair to say that you could have a family of curves on the graph, each one representing a different grind, all parallel but shifted to the left for finer grinds, showing that it takes less extraction time (and you end up with less total volume) to obtain the various flavors?

User avatar
mariobarba

#16: Post by mariobarba »

Now I'm confused. I understand extraction time to be the time it takes to achieve a certain volume of liquid. It could mean the time it takes to extract certain flavours? In my experience, any time I grind finer the flow rate decreases and so the first definition of extraction time is longer. I have not experimented enough to say what happens with the second definition of extraction time.

User avatar
another_jim
Team HB

#17: Post by another_jim »

Sorry for being unclear.

In general, the finer the grind, the less time is needed for extraction. For instance, a very coarse grind requires a 4 minute french press, while fine espresso grind does the same job in 20 to 30 seconds.

But to say that for espresso alone is misleading. For espresso, it's more a question of asymptotic extraction, that is, at what level of extraction the shot starts running blonde, and the active extracting ends, and the extraction percentage stays constant. The finer you grind, the higher the extraction before it levels off.

Here's a corrected graph that makes the actual process clearer:

Jim Schulman

Flair Espresso: handcrafted espresso. cafe-quality shots, anytime, anywhere
Sponsored by Flair Espresso
fizguy

#18: Post by fizguy »

Excellent! Thank you for indulging me. I think I get it now.

User avatar
another_jim
Team HB

#19: Post by another_jim »

I should thank you guys. I need to learn how to say this stuff easily and clearly.
Jim Schulman

User avatar
mariobarba

#20: Post by mariobarba »

I would love to Vulcan mind meld you Jim. Then you wouldn't need to take the time to make beautiful graphs to illustrate the science of espresso to us. It would be win win. :D