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Date: 11 Mar 2007 17:35:04
From: gscace
Subject: Pressure profiling update number 2
Howdee:

Well I feel quite intimidated to post my paltry attempts at learning
about pressure profiling after the Ken and Jim juggernaught published
their freezing results. But here goes.

I had time this weekend to devote to coffee since Casey and Anneke are
off visiting relatives. So two group of people came out to play with
pressure profiling. On Saturday, Alan Munter, Sarah Munter, and
Nicholas Cho showed up for a lunch of smoked salmon and asparagus,
with coffee for desert. Also at the house was my friend Dave Arnoff,
who had just received a Brewtus as a gift, and was diving into
espresso - once we fixed his machine. That's another story.

Saturday's testing was not blind, but involved everyone standing in
part of my basement, in relatively close proximity to the espresso
equipment. Fortunately everyone seemed acceptably clean and well
bathed. Nick brought coffee with which he is very familiar -
Counterculture Toscano. Nick led the way, pulling shots in which the
extractions were divided into thirds by time, with the collected
volume in each third contained in a separate shot glass. It was
pretty interesting to taste what was coming out of the spouts. The
thickest mouthfeel was in the beginning third, and also the sweetest
taste. The last third was watery and bitter by comparison. It made
sense to try to limit the amount of liquid extracted in the last third
in comparison to the amounts extracted in the first and second
thirds. I adjusted the pressure profile to accomplish this. The
pressure profile was adjusted so that the maximum pressure was 140 psi
at the pump, which corresponds to about 135 at the cake, under WBC
flow conditions. At extraction's end, the pressure was 60 psi, just
enough to keep flow going thru the cake. Nick was of the opinion that
the pressure was too high, so I adjusted the profile downward in
pressure, eventually settling on a value of 110 psi max. That's 7 2/3
bar under WBC flow conditions, but over 8 in no-flow equivalent
pressure (what a dumbass unit, huh?). This made the shots thicker,
but smaller in volume, well less than an ounce. This morning, I made
a Nick-style shot and weighed it at 18g of syrup extracted from an 18
g cake. I have to say that Nick's shots ended up being very sweet,
and I became a bit of a convert, until I tried to replicate them
today. I haven't said much up til now about profiling vs. constant
pressure. But we tried both, with Nick leaning toward profiling and
thinking that there was enough to it that maybe I oughtta think about
bringing the pump system to Portafilter 2007 in just over 2 weeks.

Today a different cast of malcontents showed up, including Steve
Jones, the famous Eric S., and Kurt Heinrich. All are schooled in the
art (just in case I need to invoke the "obvious to one schooled in the
art" schtick later). The idea was that if Nick's pressure profile
brought out the sweetness in Counterculture's Toscano, I should be
able to brew shots of Toscano using profiling and not using profiling,
nice volunteer tasters should be able to discern differences and the
differences should demonstrate a preference for one pressure method
over the other. Or not. During the tests one person acted as a
runner between me and the folks out on the deck basking in the late
winter sun (actually very pleasant). In this way the tasters wouldn't
know whether or not pressure profiling was being used, and they could
make disparaging comments out of earshot. The runner rotated after
every few shots, so only two of the three got to taste any one shot.
11 shots were brewed. Shots 1 and 2 were not profiled, with both
tasters preferring shot 2 to shot 1. Shot 3 was profiled, with both
tasters preferring shot 3 over 2. Taster 1 called shot 3 slightly
sweeter than 2 with sweetness lingering longer. Taster 2 wrote "very
sweet on the tongue immediately, excellent mouthfeel. Shot 3 was his
favorite of all shots tasted. Taster 1's notes on shot 4 (also
profiled) seem to prefer shot 4 for a combination of bright sweetness
and caramel. Taster 2 found it bright initially, but better tasting
in a longer sip. My notes for shot 4 indicate that I made a grinder
adjustment in the coarser direction since shot 3 was pretty short in
volume. Taster 3 replaced taster 2 for shots 5-8, and taster 1 for
shots 9-11. Shot 5 was profiled. Taster 3 reported "nice mouthfeel -
delicious". Taster 1 said "slightly acidic - minimal sweetness" -
Hard to know if taster 3 was calibrating his taste buds while taster 1
was getting tired. Shot 6 was brewed at constant pressure (no
profile). Taster 1 noted "hint of bitterness on 1st sip. Slight
bitterness on 2nd sip, overall slightly muddy". No preference was
given between shot 6 or 5. Taster 3 clearly preferred shot 5 to 6.
Shot 7 was not profiled. Taster 1 liked shot 7 as very clean, bright,
hint of chocolate and very sweet. Taster 3 also liked this shot,
comparing it favorably with shot 5, his first. He added that there
was a touch of bitterness in the last part of the shot. Shot 8 was
not profiled, and I ran out of Toscano, substituting some coffee that
I had roasted a week ago. Both indicated preference for previous
shots (there ya go about my roasting, huh?), with Taster 1 writing
"very thick mouthfeel, but most unpleasant shot so far. Muddy flavor
combo, nothing stood out." Taster 3 opined "no "nose". Ok mouthfeel
- same as 6.

So far, shot 3 (profiled) stood out as particularly good. Taster 1
seemed to be able to discern the switch back to un-profiled in shot 6,
with preference for shot 5. Taster 3 also preferred profiled shot 5
to unprofiled shot 6. Both tasters picked up that shot 7 was better
than 6 even though both were unprofiled. My notes for 7 indicate that
the height of my tamper in the basket indicated that I updosed it
compared to my norm, and the extraction time was long at 32 seconds,
compared to shot 5 at 26 secs and shot 6 at 24 seconds. Here updosing
and resulting long extraction time seemed to trump everything else.
Both tasters knew something was up on shot 8. Of course what was up
was that I had changed coffee.

Taster 2 replaced taster 1 at this point. Shot 9 was profiled, and
shots 10 and 11 were not. Taster 2 preferred shots 10 and 11 over
shot 9, noting that shot 9 was much like 4, his least favorite, and
that shot 10 was pleasantly bright with some sweetness and 11 was the
mellowest of 9 -11. Both 10 and 11 had good mouthfeel. Taster 3
clearly preferred shots 10 and 11 over 9, with 10 and 11 both
"possessing earthy taste, then sweet."

I possibly obfuscated the results for shots 9 - 11 by trying to do a
better job of grinder control. I brought my Kony home from work, with
the idea that I would set the Robur for pressure profiling, set the
Kony for non-profiling, then halfway through the tests, switch
grinders so that the Kony was grinding for profiling etc. In practice
there was just too much stuff going on. First, only one grinder (the
Robur) was filled with Toscano, so no Kony action could happen early
in the tests. The opportunity for using both grinders presented
itself once both were loaded with the same coffee (apr=E8s switch).
Unfortunately, by now the tests had progressed fairly far, and I just
introduced something new into the mix.

By now everyone's taste buds were pretty blown out. And the results
were somewhat inconclusive in one sense, but conclusively showed that
I am pretty inexperienced at this. I learned that there is a really
limited number of shots that can be tasted before it just gets hard to
taste. That means ya gotta keep it simple. I can't tell if shots 10
and 11 were preferred over 9 by virtue of grinder choice, or by not
pressure profiling. By looking at folks' preferences it appears that
a difference could be discerned, but then there was that shot 7, the
updosed-non-profiled one that got good ks. That means that the
level of benefit is of the same order as the noise between shots made
by an amateur barista using good equipment and fresh coffee. That is
to say that it's a real bitch trying to be consistent enough to
discern the gain or lack of it.

Afterward, we celebrated our adventure with more coffee (not Canadian
Club you lush). The reason we did this was because we sat around
discussing the shot volumes that I had produced. For these tests we
used the pressure profile that Nick seemed to like. In my opinion,
Nick's profile automatically limited the amount of coffee volume
because the pressure values were generally so low. I think everyone
thought the shots were very small in volume compared to the amount of
coffee used, so I reloaded the profile I had been using before Nick's
arrival. This profile ramped to 140 psi, rather than 110, so it
represented a substantial difference. With this profile, shots were
produced with more volume by at least a factor of 2, with viscosity
well-controlled at the end of the extraction. Visually, the shots
were of satisfactory volume compared to what the tasters expected of
an espresso made with 18 g of coffee - that is to say a double. With
crema, the volume was at least a factor of 2 greater than produced by
the Nick profile. The tasters liked them for their balanced taste and
good mouthfeel, and so did I. But that's about the gist of it. We
couldn't do any more testing if we wanted to.

My opinion so far: First, I think the idea of controlling volumetric
flow rate during the extraction by varying pressure has merit because
the extraction fractions that I tasted in shots that were parsed out
into thirds tasted best in the first two thirds, and worse in the last
third. Thanks Nick for demonstrating this to me on Saturday. Doing
the evaluation is devilishly complicated. Eric rightfully points out
that isolating a single variable is impossible when investigating
pressure profiling. For example, not-profiling requires a coarser
grind in order to keep the shot volume the same, so that means
particle size is now different and we're comparing pressure profiling
with fine particle size to non-profiling with coarser particle size.
Which cart is driving which horse and by how much? My hat's off to
people (Jim and Ken) who can pull off days of shot testing. It's hard
as hell to be consistent. That being said, I'd like to do the
tasting experiment again. I learned that one really has to keep it
simple because it's pretty difficult to do the tasting. Thanks to
Nick, Alan, Sarah, Steve, Eric, and Kurt for their help!

More when I get something worth spouting off about.

-Greg





 
Date: 12 Mar 2007 04:13:49
From: Marshall
Subject: Re: Pressure profiling update number 2
On 11 2007 17:35:04 -0700, "gscace" <gregory.scace@nist.gov >
wrote:

>Howdee:
>
>Well I feel quite intimidated to post my paltry attempts at learning
>about pressure profiling after the Ken and Jim juggernaught published
>their freezing results.

Apparently an all-out effort to create the most disgusting environment
ever seen on a brewhead doesn't earn you any respect around here. :-(

shall


 
Date: 11 Mar 2007 20:29:01
From: Ken Fox
Subject: Re: Pressure profiling update number 2
"gscace" <gregory.scace@nist.gov > wrote in message
news:1173659703.920459.67510@t69g2000cwt.googlegroups.com...
Howdee:

Which cart is driving which horse and by how much? My hat's off to
people (Jim and Ken) who can pull off days of shot testing. It's hard
as hell to be consistent. That being said, I'd like to do the
tasting experiment again. I learned that one really has to keep it
simple because it's pretty difficult to do the tasting. Thanks to
Nick, Alan, Sarah, Steve, Eric, and Kurt for their help!

More when I get something worth spouting off about.

-Greg

Welcome to the joys of trying to use the scientific method to evaluate
espresso:-)

Whenever Jim and I have done one of these projects we invariably get
comments of, "could you just extend the study a little and test . . . . ."
I can't speak for Jim but my reaction, from the gut, is "you have got to be
joking!" These things take forever to plan and are genuinely painful to
execute. By the time you have completed one, there is this overwhelming
feeling that if you never did another one, it would be too soon. And the
more complicated they become the harder they are to execute. In the just
completed freezing study, which Jim managed to weasil out of having to do
any tasting in:-) , every shot required following a program dictating what
coffee was ground by what grinder and went into which portafilter destined
for which machine. After the caffeine buzz got established, it was really
hard to keep things straight. So I had to double and triple check these
things which itself added to the fatigue.

I like my testbed because with the two machines it is possible to pull
simultaneous shots and its easier, from an experimental design standpoint,
to compare two shots in real time then it is to try to compare something you
drank 12 minutes ago to what you are drinking now. Plus, as you are
discovering for yourself, our innate human tasting apparatus is not good for
an unlimited number of espresso shots in one sitting.

The solution is clear; you need another LM.

ken
;-)