I'm sure quite a few of you are following the Barista Hustle, which is Matt Perger's weekly class/discussion/internet thing. The comments section are where a lot of the gold tends to settle. In there, Matt suggests that for a given grinder setting, the coffee that takes the most time to brew a particular amount of espresso is the most soluble. This seems congruent with my own experience, but I haven't put a fraction of coffees through the paces as he. If this heuristic actually holds water, it's an incredible piece of info.

How is that different from saying grind finer for increased extraction? If I slow the time that the shot completes, by either lower flow or pressure, finer grind,etc allowing more time at the last half of the shot where the larger molecules that are generally less quick to extract, allowing them more time to extract, thru a bed with less resistance, should lead to a higher extraction yield.

Some of the most intense, well extracted shots on the Slayer are shots that are done with pre-brew only, drawn out for crazy lungo amounts of time, with talc fine grind size.

I think Matt has done a lot for coffee and he has a lot of good stuff to say, but I also think he tends to take certain concepts, change the wording around and put a ribbon on it as if it was his own novel idea. Then people jump on the bandwagon like he's coffee messiah.

In this case, Perger's definitely repackaging the general idea in the post; in this case, I first heard about Wille / Heart doing solubility matching / pairing in Kaminsky's NRF presentation on espresso.

But I also have to give him credit for the shot time argument. That seems to be approximately correct. Although I'd be concerned that other factors could confound results. For instance, denser beans might restrict flow more effectively. Or darker roasts with more fines could restrict flow better. As a heuristic, it seems pretty good but not a substitute for a refractometer.

TomC wrote:How is that different from saying grind finer for increased extraction?...

I realize what I wrote could have been interpreted that way. What Perger suggests is much more interesting and novel.

For a given grind setting, solubility is inverse to flow rate.

NoStream wrote:...As a heuristic, it seems pretty good but not a substitute for a refractometer.

I'm curious just HOW good it is. It would seem enough variables exist to confound for sure. It's just a matter of how strong the correctional is.
Now that it's warmer at the roastery I'll start using the VST a bit more to test. (it doesn't work in the cold).

I realize the title was supposed to read "solubility" not "extraction".... if it's possible to change it, that would be great.

I changed it for you. Let me know if the pencil icon in the upper right corner isn't working for you though. It should allow you to edit your title, I believe.


I think I get what he's aiming at, I just think it's re-wording of what is already known. Solubility refers to the substance, not the method or metrics by which something's derived. Coffee that is less soluble needs longer time to reach a certain extraction, and vice versa.

If I take "X" grind and brew it for 20 seconds ( or "Y" flow rate), I get a certain extraction.

If I take the same "X" and brew it longer, say 30 seconds,( or "Y" x 1.5 flow rate) there should be a slightly albeit higher extraction.

This should hold true for any percolation style extraction where the solvent is just water, be it pressurized in an espresso group, or a pour over brew.

I don't know why this would be considered novel.

This is how I intepret what Matt and Marshall are trying to say:

Given two coffees roasted differently, both ground at the same fixed grind setting X, pulled it as espresso.

Coffee A is a gusher.
Coffee B is normal expected flow.

Based on the 'hypothesis', coffee A is less soluble than coffee B.

In another word, if a coffee calls for a much finer grind setting (when dialing in), the coffee is not very soluble on the solubility scale. Vice versa. And based on the 'hypothesis' of course.


Note: editted in bold due to my confusion, as pointed out by another member

Newbie commenting here.

What does he mean by solubility? Is it the rate of which the compounds in the puck is extracted? Or is it the strength of the espresso?

Suppose two coffees is ground at the same grind setting and have a different brew time, wouldn't this indicates that the two coffee grounds have different particle size distributions? Could this explain the hypothesis?

thomas5267 wrote:Newbie commenting here.

What does he mean by solubility? Is it the rate of which the compounds in the puck is extracted? Or is it the strength of the espresso?

The strength would be the TDS of the beverage derived from the extraction. Where you hear extraction being discussed, think of the material that's being extracted. When you hear strength, it's the resulting concentration of those extracted substances in the beverage.

Simply put: Extraction= The amount removed from the coffee
Strength= The amount of those materials now in the beverage

thomas5267 wrote:Suppose two coffees is ground at the same grind setting and have a different brew time, wouldn't this indicates that the two coffee grounds have different particle size distributions? Could this explain the hypothesis?

For comparisons sake, you have to keep other variables the same. If you want to know the TDS of something based on varying flow, you need to keep the sample the same. Same coffee, same dose, same grind.

Change any of the above and the results are skewed.

As far as solubility, look at it this way. Rock salt has a certain degree of solubility, Brown sugar has a certain degree of solubility, as does coffee and all coffees have different levels of solubility as well. The solubility is based on the substance in question itself and isn't determined by stating anything about flow. Yes, physical changes in a structure change it's solubility, i.e. grind and mass (dose).

Stating that for a given grind setting, solubility is inverse of flow rate is another way of saying that a given coffee that is less soluble will require more flow thru it in order to acheive the same level of extraction, or a longer brew time. This isn't a novel idea. But perhaps his wording of it is simpler to remember.

TomC wrote:As far as solubility, look at it this way. Rock salt has a certain degree of solubility, Brown sugar has a certain degree of solubility, as does coffee and all coffees have different levels of solubility as well. The solubility is based on the substance in question itself and isn't determined by stating anything about flow. Yes, physical changes in a structure change it's solubility, i.e. grind and mass (dose).

I am confused. I don't think solubility is a concept that can be meaningfully applied to coffee beans. Solubility is a equilibrium concept, at least in high school chemistry. It is a measurement of the amount of substance that can be dissolved in a fixed quantity of water at a fixed temperature when the substance and its dissolved form is in equilibrium. Put it in another way, it is the amount of dissolved substance in a saturated solution at a fixed temperature. The surface area of the substance or the mass of the substance added to the solvent has no effect on its solubility. It only affects the time it takes to reach saturated solution. I don't think most people drink their coffee when it is in equilibrium with the coffee grounds. We separate the coffee grounds from the coffee before it is in equilibrium, i.e. overextracted. I think in coffee making it is the extraction rates of compounds that matters, not the equilibrium concentration of the dissolved compounds.