Extraction via heat or pressure
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Katran
- Posts: 26
- Joined: 3 years ago
I changed my Linea Mini from 9 bars to 6 bars, and I notice that the coffee is less bitter (sweeter), just like others have noticed. Also, when doing french press, if you remove some of the beans just before pressing, you extract more with heat and less with pressure, and in my experience the french press becomes less bitter (sweeter).
It looks to me that the same effect is in both experiments, and it comes down to how you extract. Some extraction is done by the heat, other by the pressure. In both cases reducing the pressure reduced the bitterness. Is this right? Is it the same principle in both cases?
thanks,
--mike
It looks to me that the same effect is in both experiments, and it comes down to how you extract. Some extraction is done by the heat, other by the pressure. In both cases reducing the pressure reduced the bitterness. Is this right? Is it the same principle in both cases?
thanks,
--mike
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Jeff
- Team HB
- Posts: 6941
- Joined: 19 years ago
I think both observations are important and useful in getting coffee you like.
I'm not sure they're due to the same effects though. At least as I think about it, espresso is primarily a percolation extraction (flow through the grinds), where press is an infusion extraction (soak the grinds). The pressure differences between the two methods are very different as well.
For the press, you might be "squeezing" the grinds and pushing out some less-tasty components. I never really "pressed" my grinds, but more used the screen as a filter. If you're actually squeezing the grinds, you might try leaving the screen relatively high and decanting your coffee.
On espresso, I found that on my vibe-pump, E61 HX running a lower blind pressure gave me results that I enjoyed more than the usual "9 bar". I generally find that peak extraction pressures around 6-8 bar on my DE1 (measured in the basket) a bit more to my liking than those that are around 9 bar or higher. That I almost always run a declining pressure profile during extraction makes this not quite a one-to-one with a conventional pump machine, more like a lever. There is some interesting physics that isn't completely explained with espresso pucks where somewhere around or above 9 bar the flow can drop with increasing pressure, rather than increasing as you'd expect.
Bottom line, set things where you get the best coffee!
I'm not sure they're due to the same effects though. At least as I think about it, espresso is primarily a percolation extraction (flow through the grinds), where press is an infusion extraction (soak the grinds). The pressure differences between the two methods are very different as well.
For the press, you might be "squeezing" the grinds and pushing out some less-tasty components. I never really "pressed" my grinds, but more used the screen as a filter. If you're actually squeezing the grinds, you might try leaving the screen relatively high and decanting your coffee.
On espresso, I found that on my vibe-pump, E61 HX running a lower blind pressure gave me results that I enjoyed more than the usual "9 bar". I generally find that peak extraction pressures around 6-8 bar on my DE1 (measured in the basket) a bit more to my liking than those that are around 9 bar or higher. That I almost always run a declining pressure profile during extraction makes this not quite a one-to-one with a conventional pump machine, more like a lever. There is some interesting physics that isn't completely explained with espresso pucks where somewhere around or above 9 bar the flow can drop with increasing pressure, rather than increasing as you'd expect.
Bottom line, set things where you get the best coffee!
