roastini wrote:Hi, all. Here is some data the folks reading this thread might find interesting.

I've been using my Decent DE1+ and its advanced profile feature to preinfuse at moderate volume (3 mL/s) into a 16 g. puck until I detect just a bit of back pressure (1.3 bar), and then letting the puck bloom for 30 seconds (I have the machine pump as necessary to maintain 1.0 bar of pressure - but in my most recent shot this literally meant no pumping at all during the bloom). After the bloom, I pump as necessary to achieve an estimated flow into the cup of 1.5 mL/s, and stop my shot at about 40 g. in the cup (2.5 : 1 ratio).

I don't have a refractometer, but using a somewhat similar approach and a similar grinder, Scott Rao has reported a 24% extraction. That suggests that post-shot my portafilter might have been down to about 12 g. of coffee grounds (with the rest in the cup).

I weighed my PF before and after my shot, and the post-shot PF weighed 30 grams more, but the puck was sloppy wet. I gently poured off the excess water, which reduced the weight difference to 21 g. Assuming that ~4 g. of coffee was extracted into the cup, that implies ~25 g. of water in the puck, which is consistent with the presumption that a puck can absorb 2x its weight. (If you assume an extraction of about 23%, you end up pretty much exactly at 2x for the water:coffee ratio in the final puck.)

Nothing new from that data, really, but I find it interesting to see what information can be pulled out of the DE1+.

Michael,

Thanks for sharing. I read that from Rao and put a few comments on the "Blooming": increasing the evenness of extraction? topic over in the levers forum. I'm really intrigued by this rest period. I've long been a proponent of letting the coffee bloom and allowing the puck to swell prior to cranking up the pressure. If you look at Tije's clear portafilter videos, you can see that with the Pavoni, the puck swells during extended preinfusion, but with the Rocket, no such swelling occurrs. I think this is an indication that the pressure is an impediment to complete puck saturation and thus preinfusion. Some may argue that the water is getting in there anyway, under pressure, but I don't buy it. Water is incompressible, right? So if the puck swells when an incompressible fluid permeates the grounds under low pressure, how then can we argue that the same incompressible fluid permeates the grounds if they don't swell when pressure is applied? What's making the puck swell if it's not water?

At any rate, a 24% extraction at a relatively low ratio of 1:2.5 is an impressive feat, but what does it taste like? I'm interested to hear what qualities these "blooming" shots are taking on that a more traditional profile is not delivering. How's the body? Is it sweetness you're after? Complexity? Balance? Do tell, please. The "bloom pause" is something I'll be able to do once I get my needle valve installed, so I've been thinking about this lately.

Thanks again for chiming in,

Cheers!

- Jake

Jake_G wrote:I think this is an indication that the pressure is an impediment to complete puck saturation and thus preinfusion.

On Nuova Simonelli site, there is indeed a note that for "effective pre-infusion, water pressure should not exceed two bars when it enters the group". However, as far as I know, this pressure is in many cases 2-3 bar, with exception of most lever machines where it is equal to the boiler pressure, hence lower (generally up to about 1.5 bar)

The question now is, which option is better:

a) have constant preinfusion pressure before rising to the brew pressure (boiler lever machines)
b) have reasonably small flow and let the pressure rise gradually, due to compression of air above the puck (like most cases using DE1)
c) let the pressure rises up to certain value, then pause the pump/water flow and wait certain time, before rising it up to the brew pressure (like above)

And another question for option "a" - what is the correlation between the time and pressure, in a sense if for instance the pressure is 1.5 bar instead of 1 bar, should the time be longer or shorter ... and is there an optimal PI pressure and time combination (for particular coffee at least)

For option "b", options would be linear or progressive pressure rise etc

Whoa. Just tried "Blooming" the coffee....

Let it get about 20ml water at 80ml/min, and then pulled the flow control all the way down and waited 10-15 seconds.... Flow rate increased even more than the long PI did...

Is there more space between the granules for water to pass through? Is PI and blooming merely a way to increase the surface area of the coffee?

vit wrote: The question now is, which option is better:

a) have constant preinfusion pressure before rising to the brew pressure (boiler lever machines)
b) have reasonably small flow and let the pressure rise gradually, due to compression of air above the puck (like most cases using DE1)
c) let the pressure rises up to certain value, then pause the pump/water flow and wait certain time, before rising it up to the brew pressure (like above)

I think "a" is actually "b" in nature, with a stepped pressure cap that is lower than brew pressure, but I see your point. Line pressure preinfusion would fall into "a". Also, in "b" I think the air is compressed because the puck begins developing back pressure, but certainly more air in the system slows down the pressure ramp so again, I see your point...

AssafL wrote: Let it get about 20ml water at 80ml/min, and then pulled the flow control all the way down and waited 10-15 seconds.... Flow rate increased even more than the long PI did...

I was curious about this. The question in my head was whether expanded grounds would have more "room to breathe" or if something else is going on. What if the swelling is stopped short by the shower screen? Does that cancel the effects altogether? Does it prevent bloom/swelling the same as fluid pressure does? Very interesting to see that 10-15 seconds was enough to have a noticeable effect. I wonder what the curve of influence looks like. Like all things, I'm sure there is a sweet spot in there for each specific coffee...

vit wrote: And another question for option "a" - what is the correlation between the time and pressure, in a sense if for instance the pressure is 1.5 bar instead of 1 bar, should the time be longer or shorter ... and is there an optimal PI pressure and time combination (for particular coffee at least)

Excellent questions. I think Assaf's findings suggest there is a continuum for sure. I've got to track down Dominick's post of the Synesso document around their staged pressure profiles from a few years ago. They tracked flavor profiles by virtue of pressure and duration at different stages of the shot. Here it is:
Variable Pressure Infusion Modification Results: a Paper

I think we're in a position to continue this work. It appears they abandoned longer preinfusion times because the shots flowed too quickly. Makes you wonder why they didn't follow through with the next iteration of testing and just tighten the grind up and see what was around the corner...

Thanks guys!

- Jake

Ooh, I almost forgot. I added some pictures and EY% data to my SSP topic over in the grinders forum. I'll probably put them in tomorrow morning...

Jake_G wrote:At any rate, a 24% extraction at a relatively low ratio of 1:2.5 is an impressive feat, but what does it taste like? I'm interested to hear what qualities these "blooming" shots are taking on that a more traditional profile is not delivering. How's the body? Is it sweetness you're after? Complexity? Balance? Do tell, please. The "bloom pause" is something I'll be able to do once I get my needle valve installed, so I've been thinking about this lately.

Well, Rao got 24%. I don't know what I got. Post-shot puck weight math suggests, maybe, 23%.

I get a very chocolatey, fairly full-bodied cappuccino using a fairly dark roast and a Central American bean. My tentative conclusion is that I get more complexity with 16 g in an 18 g basket versus in a 15 g basket. My hypothesis is that the puck runs out of space to bloom in the smaller basket, but that's not confirmed yet by any means.

Jake_G wrote:I think "a" is actually "b" in nature, with a stepped pressure cap that is lower than brew pressure, but I see your point. Line pressure preinfusion would fall into "a". Also, in "b" I think the air is compressed because the puck begins developing back pressure, but certainly more air in the system slows down the pressure ramp so again, I see your point...

I had in mind experimenting with this with Flair, where I can a kind of emulate both pressure curve (using the scale) and flow (using the speed of lowering the lever) while amount of the air (below the piston) and it's influence is minimal. Device however has other limitations regarding temperature control and obviously I can't eliminate some "0 bar preinfusion". In case of pump espresso machines, amount of air and water flow (or water debit as called here) have influence on the speed of pressure rise, of course

Jake_G wrote: What if the swelling is stopped short by the shower screen?

This should be evident by imprint of the shower head on the puck, at least it was when I was using my cheap DeLongi machine if I overfilled the basket

Jake_G wrote: I've got to track down Dominick's post of the Synesso document around their staged pressure profiles from a few years ago. They tracked flavor profiles by virtue of pressure and duration at different stages of the shot. Here it is:
Variable Pressure Infusion Modification Results: a Paper

Yes, I'm familiar with it, actually I also posted a link to it in the other thread a few days ago. However, it was done with PI pressure about 3 bar (1st stage), where the sweet spot was 4-5 s or so. In case of lever machines, we are talking about lower pressure. The same with DE1, where due to flow limitation because of the thermocoil heat capacity, pressure is usually staying below 1 bar or so for 10-15 or more seconds (depending on parameters), according to various posted graphs at least

vit wrote: However, as far as I know, this pressure is in many cases 2-3 bar, with exception of most lever machines where it is equal to the boiler pressure, hence lower (generally up to about 1.5 bar)

Any tank-fed E61 offers the boiler pressure preinfusion at the "just past midway" brew lever position as long as the pump switch is appropriately positioned.

Jake_G wrote: The question in my head was whether expanded grounds would have more "room to breathe" or if something else is going on.

I believe something else is going on as well. I've always done the boiler pressure preinfusion with the levers, so I didn't notice until finding a way to do it on the E61 that the pours were absolutely faster thus requiring a finer grind. The finer grind leads to better extraction and a much tastier shot. I'm inclined to think there may be a lubrication type effect from the puck saturation.

Tonefish wrote:I'm inclined to think there may be a lubrication type effect from the puck saturation.

What do you think is being lubricated, Jim?

In general, if the preinfusion makes the pressurized extraction flow go faster, I just naturally think "lubrication." If I had to guess, or offer a possible explanation, perhaps the expansion of the puck allows the extraction of oils more easily than when compressed, and then when everything gets compressed back together during extraction, as the water grabs (or pushes) the solids, the pathways are now lubricated by the oils. Of course, that's just one guess of many possible explanations of what is happening.

EDIT: Clive Coffee Blog says fats (oils, lipids) extract very early. Oils (lubricant) flow early .... sounds good. They say acids do too. I wonder if that could help the other parts of extraction too, since some acids in some conditions can tear things up.