NoStream wrote:There are two potential benefits. One is just that you fully saturate the puck. The second is the traditional bloom-CO2 thing. I'm more convinced of the first than the second.

Yea, I tend to agree that saturating the puck for a more uniform extraction and a finer grind for a greater extraction is where the payoff comes from.

I'm not convinced the two aren't interrelated.

To Walt's point, a spent puck is pretty much the same at the end of a shot regardless of preinfusion (to a point, my slower preinfusion pucks are generally softer and tend to fall out of the baslet, whereas my quicker shot pucks are harder and knock out with a bit more effort required, but I digress...). Point being, from the outside, all pucks are wet-ish.

When I think of complete saturation, I think of pancake batter. You know how you can have your batter all mixed up and it's all definitely wet, and then you get few clumps of dry flour encapsulated in a batter bubble? I think puck saturation is about giving the batter bubbles a chance to pop and let the water in, but instead of pancake batter, where it's a whole bunch of little grains of dry flower stuck inside, it's just a single grain of ground coffee, with soluble solids inside. When the C0₂ leaves the grain, imagine the batter bubble popping, and the flour inside getting saturated.

I suspect that while C0₂ is inside the grains of ground coffee, there is less room for water to permeate through and dissolve the solids. Following this logic (or lack thereof) if one wants to completely saturate the puck, the coffee must bloom. Quick ramps up to pressure certainly impede this process, but rests, along with super slow preinfusion should help foster this.

You still have the issue of extracting these dissolved solids from the grains, which is challenging as there isn't much you can do to convince them to leave their respective homes other than pull a lungo shot and allow diffusion to pull the higher concentration of solids from within the grounds. But even short shots when pulled in this fashion have the benefit of an initial charge of water that is ~40-60% of your shot volume that prepares the puck for the second half of the shot, which is essentially washing the solids out of the puck with clean(er) water.

I'm certifiably Nutz, so take this anecdote with a grain of salt

- Jake

Funny that this is now called "blooming." I'm sure I'm not alone in using a long preinfusion on levers for years, with the intention of saturating the puck for an even extraction. I watch the drips start to emerge from a bottomless portafilter. First they increasingly distribute themselves evenly around the cup. Then when the frequency of drips consistently slows it's time to pull the shot because the coffee cake has swelled with water.

Yes, I've called it "active preinfusion" and have been blooming my lever extractions for 10 years or more. It certainly changes the character of the espresso more to my liking and I get uniform extractions with zero spritzing on >90% of my shots, probably >95%.

I always thought bloom was just to get rid of the bitterness of CO2, but I just saw a pourover tutorial that changed my mind a bit. It said that when CO2 is exiting the cell, it interferes with the water passing through the cell at the same time.

I'd like to see an experiment (@socraticcoffee) where you compare TDS of bloomed and not bloomed espresso, in 2 day-old vs 2 week old coffee.

So how long do you guys have this preinfusion and what is approximate pressure/flow profile of it ?

I know that some members do this with Flair as well. I've been experimenting with it since I bought it, but for me, beyond certain point, it doesn't help improving the taste. With other levers, there is at least some indirect heating of the brew group, which is missing here, so once you pour the water, it starts cooling down (although not that fast when piston mounted). So longer the preinfusion, lower the average brew temperature. So there seems to be some sweet spot. At the beginning, there is always about 10s of 0 bar preinfusion, from the moment I start pouring the water until the moment I start pulling the lever (pouring takes several seconds and I have to mount a piston), and then I rise the pressure in 10-15s with the coffee starting flowing 7-8 s after I start pulling. Longer than that doesn't improve my shots, although with longer preinfusion I also grind finer

With darker roasts / blends, I was prolonging the "0 bar preinfusion phase" to even 30-40s, while measuring the water temperature in the cylinder and waiting it to drop to desired (lower) starting temperature, but the result was worse - coffee lost most of the aroma

This thread is also worth checking, although not the same thing

Variable Pressure Infusion Modification Results: a Paper

Note: acording to this https://chemistry.stackexchange.com/que ... er-below-7, pH of starurated carbonic acid (CO2 dissolved in water) is 5.6

drgary wrote:Funny that this is now called "blooming." I'm sure I'm not alone in using a long preinfusion on levers for years, with the intention of saturating the puck for an even extraction. I watch the drips start to emerge from a bottomless portafilter. First they increasingly distribute themselves evenly around the cup. Then when the frequency of drips consistently slows it's time to pull the shot because the coffee cake has swelled with water.

Yea, I'm not so sure the blooming thing has been taken further than was Rao's point. He was talking about trying to simulate a filter brew and his blooming reference was keeping in the terminology of that context. Hopefully only in this thread it has bloomed to more than that.

Jake_G wrote: When I think of complete saturation, I think of pancake batter. You know how you can have your batter all mixed up and it's all definitely wet, and then you get few clumps of dry flour encapsulated in a batter bubble? I think puck saturation is about giving the batter bubbles a chance to pop and let the water in, but instead of pancake batter, where it's a whole bunch of little grains of dry flower stuck inside, it's just a single grain of ground coffee, with soluble solids inside. When the C0₂ leaves the grain, imagine the batter bubble popping, and the flour inside getting saturated.

I just can't get past the contribution of the egg in the batter in causing this stuff. That said, I'm wondering if the high (relative) pressure extraction is pushing the CO2 out and I would really like to know what gas is in those crema bubbles. Could it be CO2, and that the coffee emulsion makes crema bubbles around it, just like that batter encapsulates those clumps?

Jake_G wrote:I suspect that while C0₂ is inside the grains of ground coffee, there is less room for water to permeate through and dissolve the solids. Following this logic (or lack thereof) if one wants to completely saturate the puck, the coffee must bloom. Quick ramps up to pressure certainly impede this process, but rests, along with super slow preinfusion should help foster this.

You still have the issue of extracting these dissolved solids from the grains, which is challenging as there isn't much you can do to convince them to leave their respective homes other than pull a lungo shot and allow diffusion to pull the higher concentration of solids from within the grounds. But even short shots when pulled in this fashion have the benefit of an initial charge of water that is ~40-60% of your shot volume that prepares the puck for the second half of the shot, which is essentially washing the solids out of the puck with clean(er) water.

nickthorpie wrote:I always thought bloom was just to get rid of the bitterness of CO2, but I just saw a pourover tutorial that changed my mind a bit. It said that when CO2 is exiting the cell, it interferes with the water passing through the cell at the same time.

I'm guessing the high pressure helps in getting the gas out of the way too.

peacecup wrote:Yes, I've called it "active preinfusion" and have been blooming my lever extractions for 10 years or more. It certainly changes the character of the espresso more to my liking and I get uniform extractions with zero spritzing on >90% of my shots, probably >95%.

another +1

In pourover, coffee blooms and CO2 bubbles go to the top, so it's easier for the water under gravitation force to do the extraction

In espresso, water is under high pressure and is pushing those bubbles towards the bottom. And, since passages between the grounds are quite narrow, actual speed of the water is relatively high, so this process is much more dramatic

Anyway, that prolonged wetting of the puck may cause differences when and how much of particular component among thousands of them in the coffee is extracted, resulting in better taste in some cases and worse in other ... or can improve other things like uniformity of extraction ...