This is fascinating stuff.

gscace wrote:I've also formed the opinion that there is something to soaking the coffee cake at a low pressure and then ramping the pressure up.

I have always thought that the argument of spring lever machines producing a superior cup due to the progressive brew pressure profile is hampered by the fact that it doesn't fully take into account the beginning of the brew. So combining the slow pressure rampup with a progressive fall of the brew pressure sounds like a logical approach to me. I may of course be wrong.

Br,
Teme

gscace wrote:WRT taste - I've been mostly investigating a lot of the physical effects of variable pressure on the extraction, and learning about how to do it. I've been doing this because varying pressure doesn't make the coffee suck. It tastes good enough to warrant spending the time learning about the system, and I am enjoying the taste and the learning process. Yesterday I pulled a couple of shots for a third party both with the profile described above, and without any profile at all. There was a difference in taste. Next weekend I hope to do some blind testing in which I brew shots for folks with both profiled and non-profiled pressure, seeking to learn if the difference can be reliably detected and which shots are preferred.

I hate to keep repeating myself; but I truly believe black box methods, which go directly from the perculation's environmental variables like temperature or pressure to taste, are a dead end.

If the the coffee in the cup isn't different, how can the taste be? If the taste is different, is it because the pressure profile profile had 6.5 bar for 13 seconds, or because there's different stuff in the cup. The answer is obvious -- science is about connecting the toe bone to the foot bone, etc. etc., not just about correlating the head bone's nods to the toe bone's taps.

The simplest set of measures are to weigh the puck before and after brewing, and to weigh the shot. This tells you how much of the puck has ended up in the cup and how much it is diluted with water. If my research on this is correct, the taste roughly follows the taste wheel -- the acid and bright bitter compounds extract first, the caramels and roast flavors later. With a straight pressure pump that I used in my experiments, most of the extraction was done by 20 seconds, and it ran at 15 to 18% for high doses, 20 to 24% for low doses in the same basket. The end of the shot, beyond 20 seconds, was mostly just water.

It sounds that pressure profiling can change this course of events and create more flexible controls. Once you know what is getting into the cup at what time, you'll know what to taste for, and how to tune your profiles.

You should put off your blind testing until you've "white-boxed" pressure profiles at least this far.

A huge hats off for coming up with a commercially viable system of doing this -- but now the job is found out how it affects the shot, and only secondarily how it affects the taste.

another_jim wrote: If the the coffee in the cup isn't different, how can the taste be?

OK, this may be true for "taste," but what about texture? 9 bar espresso coffee has notably different texture than brewed coffee, and it is reasonable to surmise that the pressure profile will influence texture -- and, directly or indirectly, influence the extraction of non-soluble flavor components that may not follow the flavor wheel's orderly scheme.

Good point. Measuring the puck weight loss for a stand-in on solubles yield is a good fast measure of cup chemistry, but says nothing about the fat/water state of the cup. A couple of useful measures may be the classic espresso ones -- in the WBC, judges drag a teaspoon through the crema lengthwise and see if it heals itself. The other classic measure is timing how long it takes for a hole to appear in the center of the crema.

A more scientific approach may be to measure the density -- more fat and more crema means less density. One can measure either by weight and volume, or one of those floating bobbin alcohol content thingies. Either way, one could measure immediately after the shot and again after the crema has a hole. If there is a systematic difference on crema and oil content for different profiles, a blind taste test with well aimed mouthfeel questions is quite likely to be successful.

As a matter of "science rhetoric," saying people like pressure profile profile X better than pressure profile Y is far less convincing than saying profile Y puts 20% more fat in the cup and 90% of tasters find the result "creamier."

Texture is an interesting point. Back when I was doing the Achille review I had the opportunity to line up a Cremina, Achille and Elektra. The texture of the Achille and Cremina were very comparable but I was pulling both. According to my manometer-on-portafilter gauge I readily pull at 9 bar. The Elektra, which produces a lower pressure with the spring, produced a noticeably lighter, less syrupy texture (fewer dissolved solids due to lower pressure?). While the arm pulled shots were very robust, thick and deep the spring lever was thinner but more refreshing, light and flavorful IMHO.

another_jim wrote:Good point. Measuring the puck weight loss for a stand-in on solubles yield is a good fast measure of cup chemistry, but says nothing about the fat/water state of the cup. A couple of useful measures may be the classic espresso ones -- in the WBC, judges drag a teaspoon through the crema lengthwise and see if it heals itself. The other classic measure is timing how long it takes for a hole to appear in the center of the crema.

A more scientific approach may be to measure the density -- more fat and more crema means less density. One can measure either by weight and volume, or one of those floating bobbin alcohol content thingies. Either way, one could measure immediately after the shot and again after the crema has a hole. If there is a systematic difference on crema and oil content for different profiles, a blind taste test with well aimed mouthfeel questions is quite likely to be successful.

As a matter of "science rhetoric," saying people like pressure profile profile X better than pressure profile Y is far less convincing than saying profile Y puts 20% more fat in the cup and 90% of tasters find the result "creamier."

I'm personally a fan of thick mouthfeel. I'm compiling some numbers on the profiled extractions. Coffee cake weight for 2 shots this afternoon is 18.1 and 18.2 g. I normally don't weight shots and it threw my method off a bit - or at least I'm blaming that - but I got one each 31 and 32 second shots, but with extracted volumes of 22.5 and a shorty at 17.6 g each. I baked out the cakes for 1 hour at 250F and an additional hour at 350F after the cakes indicated stored water at 1 hour, and the values for coffee transferred to the cup or the air is 4.0 and 3.5 g respectively. Extraction ratios defined as coffee transferred to the cup divided by cup weight = 17.8% and 19.9%.

The cup character was buttery thick mouthfeel with crema that lasted beyond me removing the shot glasses from the spouts, carrying them upstairs, and weighing them on an old mechanical balance, writing down the numbers and quaffing the elixir - several minutes anyway. Taste was of thick chocolate with bitterness well muted. Interestingly enough, the longer shot was the sweeter of the two. The coffee is a mix of Ethiopian Sidamo dry process with an Indonesian Sassandu dry-process. When it's new there's a bit of fruit, but at 4 days out of the roaster the character changes to more chocolate and thickness on the tongue.

I dunno what you and Andy are specifying for shot volume and transferred mass, but it's late and I've got a bunch of sh** to do tomorrow, so I'm going to bed. I'll get more data tomorrow when a couple of folks show up for coffee, smoked salmon, and beer. Dunno what is the teaser for what. I'll also do comparisons with the straight line pressure thang, and I'll post the profile I'm using, when I learn how to post an Excel chart.

-Greg

Bumping and old thread. It's been since 2007, and updates?

Do a little more searching on this board. This topic has received many pages of posts in the last few years (although maybe the last active thread became inactive several months ago).

ken