Effect of preinfusion time - what is best - thoughts?

[luca]

Hi guys,

I've been wondering about preinfusion lately; specifically, how much is too much? There's a test machine with some small restrictors for heaps of PI on the bench at the roastery at the moment, and I don't think that any of us really like it all that much.

It seems to me that a longer dwell time builds up more of the concentrated, chocolately flavours at the beginning of the pour at the expense of flattening out some of the more nuanced characteristics. I've noticed that even fast shots with heaps of PI time seem not to be all that sour. If you have done the exercise where you split an espresso into thirds, it's as if the first third is favoured in the end result.

That said, we had a linea with no restrictors built in for PI and it was quite difficult to use, so my current preference is for about five or six seconds dwell time.

Does anyone else have any thoughts? Has anyone experimented with different preinfusion times? (Other than Ken's experiment) Seeing as the Synesso has manual PI control, I guess that I should get on it and do some testing at some stage ...

Cheers,

Luca

[another_jim]

Ken and I used the criterion of the least amount of time that produced a fully soaked puck at the point the first drops appear. This may not mean much in terms of taste; but should be fairly solid in terms of reducing channeling and getting consistency. This time is rather dependent on your line pressure -- less pressure requires a longer time.

[HB]

It seems to me that a longer dwell time builds up more of the concentrated, chocolately flavours at the beginning of the pour at the expense of flattening out some of the more nuanced characteristics.

That's consistent with what I found in The Secret Life of Ristrettos:

As a rule of thumb, ten seconds of (extra) preinfusion equals a grinder adjustment of two millimeters coarser on the Mazzer Mini, or a reduction of coffee equal to approximately 1.5 grams (*). Running the mega-sized preinfusion "softens" the puck and opens a wider window for good extractions. My results so far for ristrettos are improved, though the opposite occurred for regular doubles, where the flavors became muddy and flatter.

But these results are far less vigorous than Jim and Ken's. The puck-slamming Elektra A3 and non-regulated Elektra Semiautomatica make one wonder about the value of preinfusion, or at least its value relative to other considerations like the evenness of its water dispersion. For my quickie experiment with the Vetrano, mains preinfusion beyond ten seconds was not a good thing, ristretto or not.

[luca]

Thanks for that, guys,

Glad to hear that all of that isn't entirely my imagination ... pulled some shots on the mega-preinfusion-modded machine today and got some gushers that actually had quite a good mouthfeel. And the coffee was too young! Probably not such a bad thing if the machine will go into cafes that aren't on top of the variables and serve mainly milk-based drinks, but I suspect that the restrictors will be changed soon!

Ken and I used the criterion of the least amount of time that produced a fully soaked puck at the point the first drops appear. This may not mean much in terms of taste; but should be fairly solid in terms of reducing channeling and getting consistency. This time is rather dependent on your line pressure -- less pressure requires a longer time.

Yep, that's exactly what Ben (at the west australian barista academy) and I do with our Synessos when we're pulling shots with the naked portafilter. Middle lever position for PI 'till we can see the beads at the bottom of the basket, then slam on. If you want to be all wordy, I guess one could say that that's the point at which the puck is "infused." ;P

That's consistent with what I found in The Secret Life of Ristrettos

Excellent. Sorta makes me wonder why the Aussie brewtus has an inordinately long preinfusion time ... seems to defeat the purpose of getting nuance into the cup through easy temp adjustability.

The puck-slamming Elektra A3 and non-regulated Elektra Semiautomatica make one wonder about the value of preinfusion, or at least its value relative to other considerations like the evenness of its water dispersion.

Good point. Sounds similar to the lineas without gicleurs - I think that the a.c guys keep saying that these lineas can get great shots occasionally, but it's difficult to maintain consistency.

For my quickie experiment with the Vetrano, mains preinfusion beyond ten seconds was not a good thing, ristretto or not.

Yikes! Were you going for 10+ seconds preinfusion and still keeping the whole shot at 30 seconds (or whatever) after lever flip? It's funny how one might talk about a 25 second extraction, but the difference in flow rate for a mere 30mL espresso is actually quite large between extractions with a PI of 5 seconds and 10 seconds ... we're talking a 25% difference!

Thanks for that, guys, interesting stuff ...

Cheers,

Luca

[another_jim]

I think the difference preinfusion makes must depend on how good the water dispersion is. On my Elektra, it made virtually no difference, presumably since the water path is good. On the Juniors it made a very slight difference in taste (and that only for some blends), far more in consistent shots.

Illy says the flow through a wet puck is different than through a dry one. A gentle preinfusion is necessary if a machine's full pressure flow is eccentric enough to cause problems in the dry puck. If the full pressure flow doesn't upset the dry puck, preinfusion may not be as necessary. Water paths out of the three way, diffusion blocks, and shower screens are dramatically different from machine to machine, so the need for preinfusion can also be different.

[HB]

Yikes! Were you going for 10+ seconds preinfusion and still keeping the whole shot at 30 seconds (or whatever) after lever flip?

No, I adjusted the grind such that the start of beading until the end of the pour was about the same as a "normal" preinfusion. But most of the time I don't use a stopwatch, I instead watch how the flow develops; if it looks good, I assume the timing was within the acceptable range.

[cannonfodder]

I added a delay on make relay to the pump on my Faema. I have the relay dialed in at 6 seconds with a 3bar mains preinfuse. That is just right on my machine. I get the very first appearance of espresso in the basket holes when the pump engages. Any shorter and I have a dry spot in the bottom center of the puck. Longer and I get pooling on the bottom of the basket which moves the process from preinfusion to infusion/percolation in my book.

To check the timing you just have to run the preinfuse cycle and stop the machine. Then remove the PF and knock out the puck onto a flat surface to see if the entire puck is wet.

On my machine the preinfuse made a positive impact but as everything espresso your experience on your equipment may vary.