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Main
Date: 09 Mar 2007 20:24:27
From: Ken Fox
Subject: Freezing Coffee Used for Espresso; a Randomized Trial
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The material in this post is crossposted with an article covering the same
research experiment, which appears on the front page of home-barista.com,
Dan Kehn's super espresso website. This post is not a complete word for
word copy of the home-barista.com article, but rather is presented in a
somewhat more "usenet-friendly" manner without some of the content that
makes the web published article more like a "magazine article." The web
article, which can be found here
http://www.home-barista.com/store-coffee-in-freezer.html is much more
"readable" than this usnet post can be; I recommend that you read it on
home-barista.com rather than here. I am posting it here in order to have it
be placed in the google alt.coffee archives so that it can be searchable at
a later date. Regardless of where you read this, I request that you comment
in either the home-barista.com thread that follows the article, or here, but
not in both locations, to avoid redundancy.
Freezing is controversial, and perhaps moreso with regards to espresso:
Few topics in coffee have been debated as much as freezing. Coffee has a
limited shelf life, even shorter when it is used to make espresso. Most
serious enthusiasts feel that this shelf life is considerably less than a
month, and many agree the shelf life at room temperature is limited to as
little as 10 days after roasting. There is no evidence that simple valve bag
packaging at room temperature significantly extends storage life for
consumers who care about freshness in coffee. Given its perishable nature,
and the fact that many consumers have limited access to good fresh coffee,
it is only natural to want to extend the shelf life long enough that a given
batch can be considered usable, near its peak of freshness.
Freezing and refrigeration of roasted coffee are hotly debated based on
anecdotal experience. Some academic research has been published, most
notably by Sivitz, however his methods, including the use of a vacuum and
extreme cold (~-40°F or C) are not available to most individuals, especially
in the home.
I prefer to make several batches in succession with my 500 gram sample
roaster because of the required heating and cooling time, which makes small
volume roasting impractical. As a result, I've used freezing as a storage
technique, and am constantly switching back and forth between previously
frozen and never frozen coffee. I have not noted an obvious difference
between these coffees prepared as espresso, however I wanted to formally
test my observations. This article presents the structure and results of an
experiment to demonstrate the effectiveness (or lack thereof) of freezing
very fresh coffee in a home environment to extend the shelf life of this
perishable product.
How can we best study this sort of question, i.e. what is the impact of
freezing on coffee, and whether it allows the shelf life to be increased?
An ideal way to compare two different consumable items is to be presented
with both of them simultaneously. This is the very nature of blind tasting
experimentation. Fortunately I have two similar espresso machines that can
be adjusted to produce nearly identical espresso extraction parameters.
Since I have the good fortune to own this equipment, and the desire to get
to the bottom of this freezing issue, I decided it was high time to explore
this subject in a more scientific manner. Out of this curiosity was born
this experiment, a definitive blind tasting trial comparing espressos
prepared from coffee that was previously frozen for periods of four or eight
weeks, to freshly roasted coffee during its normal shelf life, in this case
between 4 and 8 days after roasting.
As in any study using the scientific method, one has various factors that
may confuse or confound the results. Failure to account for the variables
may result in false impressions of real differences when in fact none exist,
or may mask real differences. It is therefore important to consider these
variables in the design of the experiment from its very conception. By doing
so, one acknowledges their presence and sets up the experiment in a way that
these variables cancel themselves out. Espresso is a variable product, even
when one uses the same coffee, technique, and equipment; there is shot
variation. This needs to be accounted for. Also, if the tasters know which
coffees they taste came from previously frozen coffee, and which did not,
they may be biased and make choices based on preconceived notions rather
than actual differences; this is the rationale for using a blind tasting
approach, where the tasters do not know what coffee was used to make any
particular espresso. In addition, the test must be designed in a way that
it takes all variables into account, balances them, and has an experimental
design that can actually be executed. If properly designed, the trial's
results can then be statistically analyzed which will show if observed
results are likely genuine, or occured by chance alone.
We held four tasting sessions, each lasting approximately three hours. They
were composed of 16 paired double shots prepared consistently and
simultaneously on the two espresso machines and presented to the taster in a
blind fashion. The taster did not know which coffees he was tasting or which
pieces of equipment were used, just that one espresso was made from
previously frozen coffee and the other was not. Each taster would have 8
paired shots to taste in a day's session; 4 pairs of shots compared coffee
previously frozen for 4-weeks to never frozen, and the other 4 pairs of
shots compared coffee previously frozen for 8-weeks to never frozen. Grinder
changes were minimized as much as possible in the design to both avoid
wasting coffee and the need to constantly clean grinders. The shots were
alternated to the tasters so that the tasters did not have undue fatigue of
their ability to appreciate differences in espresso. This was important
because espresso is by its very nature a very intense beverage, and too many
comparisons within a very short time can diminish the ability to appreciate
differences. A total of 64 paired shots of frozen versus never frozen coffee
were tasted and compared over the four day course of this experiment.
When presented with the two espressos, the taster was required to compare
them according to three factors: the crema, the intensity of the aroma and
taste, and the overall preference. These tasters were instructed to make
these comparisons quickly but carefully, in keeping with the way that such
comparison taste studies are done in industry where this method is very well
established.
A few additional words about the shot preparation and the freezing are
warranted. Double espressos were prepared with approximately 18 grams of
coffee lightly tamped and ground in a way to produce 1.25 to 1.50 ounce
shots within a period of 20 to 30 seconds, occasionally as long as 35
seconds, with very few shots at the shorter end of this spectrum. The
previously frozen coffee was frozen immediately after roasting in a very
cold chest freezer, at a temperature of around -15°F (-26°C). Frozen coffee
remained in the freezer for periods of either four or eight weeks.
TEST PROCEDURE
Below is an outline of the testing procedure; the actual execution of the
experiment was considerably more complex and is given in the appendix.
Please refer to the detailed section if you would like to know more.
Both espresso machines used identical bottomless portafilters (obtained from
espressoresource.com) and double baskets; no attempt was made to use either
portafilter exclusively with either machine. In order to minimize inter-shot
variability, I prepared all of the portafilters myself, including the
grinding, dosing, and distribution of the coffee, plus the tamping. In
practice I consistently overdose my double baskets with approximately 18g of
coffee and use a very light, approximately, 5lb tamp with a near-piston
fitting tamper.
At the commencement of the production of each shot pair, I flushed each
machine of 50ml of water into a measuring cup, then inserted the
portafilters. Identical pre-warmed white Revol porcelain espresso cups were
positioned under the portafilters and the shots were started within a second
or two of each other. A shot timer was started at the same time, and I
strove to keep the shots within a duration of 20-30 seconds each. I
personally watched the initiation of each shot to be sure that it started
normally, generally with first drops of espresso dropping off the basket
underside after 6 or 7 seconds. Once the shot was seen to be progressing
normally, I either completed it in the case where another person was the
taster, or if I was to be the taster I turned the remainder of the shot
production over to my fellow taster.
When originally conceived, this experiment was going to be done with myself
and Jim Schulman serving as the two tasters and baristas. Unfortunately, Jim
needed to change his plans and could not attend, so I enlisted the aid of
two espresso loving friends, Bob and Randy. These friends were given a crash
course in espresso preparation on my equipment, and instructed on the proper
shot volume and appearance that was desired, e.g. 1.25 to 1.5 oz, and to cut
the shot at the first sign of blonding. Neither Bob nor Randy initiated any
of the shots or did any preparation of the portafilters, a job I reserved
entirely to myself in order to keep shots as consistent as possible. Their
role in shot making was limited to turning the machines off at the
appropriate time, and to serving the shots in an identified but random
order.
Jim Schulman kindly provided a program for randomizing the effects of the
two different espresso machines and two different grinders. Each day, both I
and my fellow tester had a program sheet that gave the conditions (machine,
grinder, coffees) to be used on each shot comparison. In order to have a
truly random order of shot presentation, right vs. left, each tester used a
coin toss for each pair to determine which shot would be presented as the
"right" shot and which as the "left." The person tasting and grading the
shot did not know what was in the "right" or the "left" shot other than that
one had been made from a previously frozen coffee and the other from a
fresh, never frozen coffee. Only after the testing was completed each day
was each taster's scoring sheet decoded with the sheet used by the other
tester who presented the shots in the order determined by the coin tosses.
When presented with the two side by side shots, it was the job of the taster
to rate them according to the parameters previously described. Pictured
above is a completed scoring sheet produced in this experiment
In addition, there were other variables other than freezing which were
present in this experiment. Although these identified variables such as
grinder burr condition, espresso machine used, or taster, were intended to
cancel themselves out, in essence becoming irrelevant, Jim's experimental
design nonetheless allows us to study them separately later for any
interactions they may have with what we are studying (previously frozen vs.
never frozen coffee) as well as for any importance they may have
independently.
SUMY OF TEST PANEL TASTE RESULTS
I'm going to limit the technical and statistical minutia presented here
since the results were "negative," which is to say that there were no
statistically valid differences shown. Jim Schulman and I are planning to
write another article in the near future dealing with experimental design
and the scientific method as they apply to research into coffee and
espresso. We will probably use this study and some of its more detailed
results as examples in that paper. If you are interested in seeing the raw
data obtained in this study, it can be found in both table and graphical
form in the section at the end of this article.
When the results were examined according to the three scored parameters, the
overall preference, the crema, and the intensity of the taste and aroma, no
statistically significant differences were noted among the coffees studied
or the other variables of the study. What this means is that none of the
tasters could consistently differentiate among the shots made with
previously frozen or never frozen coffee. Similarly, none of the tasters
could consistently tell the difference based upon whether the shots came out
of the newer rotary pump driven or the older vibratory pump driven espresso
machine, nor between the two grinders, one of which had brand new burrs and
the other with more heavily used burrs.
Having participated in this trial myself, and having tasted one half of the
test's paired shots (32), I knew full well that each pair included one shot
made from previously frozen coffee and one shot whose coffee was fresh and
never frozen. Nonetheless in most instances the shots were of nearly
indistinguishable quality and any attempt to score one above the other
required imagination or discerning fine differences that may or may not have
existed. On a number of occasions I became convinced that I'd figured out
the taste characteristics of previously frozen coffee. Then, I'd try to pick
it out on subsequent shots. At the end of the day when the randomization
scheme was disclosed, I realized that I had in fact not figured out how to
differentiate between the coffees, as evidenced by the random nature of my
preferences! During the conduct of the tasting trials I received similar
comments from my fellow tasters; they were certain that they had "figured it
out," yet when we unmasked the data it was clear that they had not.
WHAT WERE THE CONCLUSIONS REGARDING FREEZING?
What exactly are we to make of this experiment and these results? There are
several obvious conclusions which I will list below, and endless further
speculation which I will leave mostly to the readers of this article.
(1) Freshly roasted coffee that is immediately frozen after roasting in a
near airtight container in a very cold freezer, can be kept undisturbed in
the freezer for at least 2 months and be expected to produce espresso shots
that are not obviously inferior to those made from fresh coffee that has
never been frozen.
(2) Freezing does not accelerate staling after defrosting: At least over a
period of time extending to about 8 days after roasting, using the roasting
and freezing procedure used here, there was no evidence that previously
frozen coffee deteriorates more quickly after defrosting than does coffee
that has never been frozen.
This study was priily designed to evaluate freezing as a method of coffee
preservation available to the average home consumer. As such, it has
demonstrated that freezing, done shortly after roasting in a very cold
freezer delays staling for at least two months and hence extends shelf life
for at least that long.
Two aspects of this study could present difficulties for some readers and
they deserve clarification. First, the coffee was frozen immediately after
roasting, and those who are reliant on parcel delivery services or who
cannot buy just-out-of-the-roaster coffee must compromise on that. The
second is that not all freezers, especially freezer compartments of
refrigerators, can maintain very cold temperatures. Self-defrosting freezers
are especially problematic in that regard. Nonetheless, I chose to use a
"best case scenario," that is, immediate freezing in a very cold freezer, to
study the impact of freezing for coffee preservation. Had I chosen otherwise
and had results been different, we would not have known whether the
compromised results were the result of delay in freezing or inadequately
cold freezer temperatures. The data in this study can be augmented by
reports of readers who have used less rigorous approaches, and I solicit
their findings in thread following this post (or on home-barista.com)
Jim Schulman has previously communicated to me the results of some informal
coffee "cupping" experiments he has done with frozen coffee. Cupping is of
course a far different process than is espresso making and some would say
that one can have more precision in cupping than one can have in judging
coffee served as espresso. Jim reported that although he could tell
previously frozen from never frozen coffee more often than if by chance, the
differences were subtle and defied characterization along the lines of
anything "systematic" or "easily describable." He felt he was no better in
discriminating between frozen and never frozen than he would be in detecting
subtle differences between different roast batches of the same coffee,
neither of which had ever been frozen. I should add that Jim does not have a
freezer that holds very cold temperatures like mine does, however he did
freeze his coffee immediately after he roasted it.
Jim's observations imply that the observations in this study can be
extrapolated to include coffee that is frozen and used in preparations other
than espresso. This would require further efforts to prove, should someone
be sufficiently motivated to try to test it.
ADDITIONAL OBSERVATIONS ON THE OTHER VARIABLES
The presence of more than one espresso machine and more than one grinder
introduced other potential variation into the study that was controlled for
by proper "balancing" within the experimental design. Because the study was
balanced in this way, it enables us to look at these other variables
independently to learn other things from this experiment. Below are some
conclusions reached as result of further data analysis that includes these
factors.
(1) Old versus new grinder burrs: There is no obvious, tastable benefit
from changing grinder burrs after moderate wear as was done on one of the
two grinders used in this experiment. Some have speculated that changing
planar grinder burrs much more frequently than is the stated life of those
burrs would produce a benefit in espresso shots. We did not detect any such
difference and therefore believe that very frequent burr changes, much
earlier than the stated lifespan of the burrs, has no detectable benefit if
taste is what is being measured.
(2) Rotary versus vibratory pumps: This study is the third independent
experiment which compares the output of two nearly identical espresso
machines that differ priily by the type of pump within them, one with a
vibratory pump and the other with a rotary pump. As in the other two
studies, [ http://tinyurl.com/2gta9m ], [ http://tinyurl.com/yv78oh ] no
consistently tastable difference was detected. Therefore, all suppositions
that rotary pumps produce superior shots to those made by vibratory pumps
must be regarded as unproven barring further experimentation.
(3) Tasters do have measurable preferences: There was only one obvious
interaction among any of these variables, which was that one taster, Randy,
rated the coffee that had previously been frozen for 4 weeks with lower
scores when he tasted it on his second session, 3 days after the first. In
addition, there were several uninterpretable ones including such things as
one taster liking one grinder/machine/coffee combination more than others.
The effects are "obvious" in a numerical sense, which is why they are
significant. However, they have no bearing on the overall result. As such
they simply make the point that on some very specific combinations of
machines, grinders, and coffees, some tasters will have idiosyncratic
preferences. The whole point of using multiple tasters is to cancel such
idiosyncrasies out. However, the presence of interaction effects disallow
blanket statements such as "No taster will ever detect a difference
regardless of machine, grinder and coffee being frozen." They prove there is
a difference between fresh and frozen that comes out in rare and
idiosyncratic circumstances. This observation in no way counteracts the fact
that the overall results offer no evidence whatsoever that there is a
systematic taste difference.
The wording of the last point is taken directly from Jim Schulman's
commentary on the data analysis, for which I am grateful and without which
this study could not have been done.
Finally, some reviewers of earlier versions of this manuscript raised the
issue of extraction percentages and how this might have effected the
results. It is true that the shots tasted in this study tended towards the
ristretto, and the double baskets were "overdosed" with approximately 18g of
ground coffee. Because this was done for all 128 shots tasted (64 shot
pairs), in order to invalidate the conclusions one would need to come up
with a hypothesis explaining how grinder fineness and dosing are
interrelated with freezing. I cannot produce a feasible explanation of why
this would be the case, and no matter how the shots were prepared some
readers would feel it was not representative of THEIR own approach. The most
important thing is that the preparation was held constant, so the impact of
the technique I used should cancel itself out in the observed results.
HOW MIGHT YOU USE THIS INFORMATION?
Freezing is a viable method of preserving the freshness of very fresh
coffee. Exactly how long the usable lifespan of coffee can be extended with
freezing is unknown, although we do know that if frozen immediately that
lifespan extends to at least 8 weeks. In this experiment, a very specific
methodology was employed, and exactly how far one can deviate from it and
expect to get good results is unclear. The previously frozen coffee we used
was frozen immediately after roasting, within about an hour, in
semi-airtight packaging in a very cold freezer (about -15°F / -26°C). It was
then defrosted, only once, within the same packaging before it was exposed
to outside air, reducing or eliminating the possibility of condensation.
If the coffee one contemplates freezing is not "fresh" to begin with, it is
doubtful that freezing will do much of anything positive. To me this means
that freezing is probably of no value when dealing with purchased coffee of
uncertain age. In the case of coffee that has partially degassed, that is
perhaps several days out of the roaster, it is unclear from this experiment
whether freezing will extend shelf life significantly. Since this is going
to be a fairly common scenario for home espresso enthusiasts ordering
online, it deserves further comment.
For the homeroaster or person who can buy fine quality extremely fresh
roasted coffee locally, it makes no sense to degass the coffee at all before
freezing as this adds nothing and the coffee can be degassed later, after
defrosting. On the other hand, if you are buying roasted coffee that has to
be shipped to your door, then you will need to test for yourselves how well
this works with the beans that you purchase. My opinion, which is not
supported by any data (since I have none) is that freezing fresh coffee that
is several days out of the roaster should extend shelf life by at least a
few weeks. I would encourage readers who use this approach to give us the
benefit of their own experiences in comments you make on the thread that
follows this article. Similarly, if you don't have a very cold freezer, it
stands to reason that the amount of time that freshness in coffee can be
preserved will be less. How much less I do not know, but perhaps some
readers will have their own observations that will prove useful.
If you are concerned about what sort of container you should use for
freezing coffee, it obviously needs to be something that is relatively
airtight and that can tolerate the conditions present in a freezer, and the
temperature stress in going from room temperature to very cold and back
again to room temperature. I generally use Mason type canning jars or
recycled jars from grocery products that will close with a tight seal; I
fill them up as full as possible to minimize the remaining air that is
present. I have also used certain types of commercial plastic coffee bags
that can be sealed and if valves are present I tape over them. If you
purchase coffee that is already packaged in a sturdy valve bag you could
simply tape over the valve and toss it directly into the freezer. I would
however suggest that whatever container you choose, it be sized to allow you
to consume all of the contents within a reasonable period, say 1 week,
without having to open the bag and return some of the contents to the
freezer; doing so risks condensation on the beans which could theoretically
cause damage.
APPENDIX
This section contains further details on exactly how this study was
performed, how various variables were controlled, actual data collected, and
the data analysis. It is recommended reading for the treatment of insomnia
not amenable to medical management:-)
COFFEE ROASTING AND FREEZING PROCEDURES
The coffee that was compared in this experiment was single origin MAO
Ethiopian Harrar Horse obtained in green (unroasted) form late in the summer
of 2006 from coffeewholesalers.com. This coffee was selected for several
reasons including the fact that it makes nice single origin espresso shots,
I had enough of it in inventory to test, and finally because it tends to
show when it is staling by losing its multidimensional flavors and becoming
"flat." All of it came in a single 11 lb bag and all batches were roasted
identically to approximately 442°F with the same roast parameters, a level
at the very beginning of second crack which produced beans with no visible
oiling. A 500g gas fired drum sample roaster was used as shown to the right.
The beans were introduced at an approximate drum temperature of 360°F, after
which first crack started between 9 minutes and 9 minutes 15 seconds, and
the total roast duration was between 12 minutes 15 seconds and 13 minutes.
Roast progress was followed with the aid of an internal thermocouple in the
roast drum, plus a Fluke digital thermometer. All of the samples, be them
fresh never frozen, or previously frozen, were the result of at least two
separate batches that were completely mixed together.
The coffee that was destined for the freezer was immediately put into
commercial plastic coffee valve bags. Excess air was evacuated by hand and
the seams of the bags were sealed. A piece of scotch tape was placed over
the valves because these valves rely on a drop of oil within the valve and
the valve can hence freeze in either the open or the closed position. Tape
was used to prevent the possible entry of air from the freezer through a
valve that might possibly have frozen open. The coffee, now in sealed valve
bags, was then put near the bottom of a very cold 7 cubic foot chest
freezer, whose measured temperature was generally in the range
of -15°F/-26°C to -20°F/-29°C on an NSF freezer thermometer. The coffee then
remained in the freezer for periods of 4 or 8 weeks as detailed earlier in
this article. When defrosted, the coffee was removed in the sealed bags and
allowed to reach room temperature in a dark kitchen pantry; the piece of
tape over the valves was removed once the bag reached room temperature.
The fresh and never frozen coffee used for comparison was roasted with
identical roast parameters as was the coffee that had been previously
roasted then frozen. It was roasted 4 days before the first day of taste
testing, and hence was tasted from days 4 to 8 in the degassing process. The
previously frozen coffee was assumed to have at least slightly aged while in
the freezer. Therefore it was decided to remove this previously frozen
coffee from the freezer 1 day later, after the "fresh, never frozen" coffee
was roasted. What this means is that if one disregards any degassing that
may have occurred in the freezer, the previously frozen coffees degassed 3
days before the first day of tasting and were tasted over a period for 3
days to 7 days out of the freezer.
OTHER ESPRESSO MACHINE AND GRINDER MAINTENANCE ISSUES
The grinders were adjusted as needed during the trial to produce 1.25-1.5
oz. double shots within a time range of 20-30 seconds, generally never more
than 35 seconds. There were a couple of instances where one or other shot
were simply not satisfactory due either to channeling, too rapid flow,
choking, or other problems. In those cases both shots were discarded and
another set was made to replace them. Every time that coffee was changed in
the grinders, the grinders were completely cleaned of what remained from the
earlier coffee. This included using a chop stix to dislodge beans that can
hang up above the grinder burrs, and also cleaning out the grinder chutes
and the dosers manually, so that the new coffee introduced would not be
"contaminated" with the old one. Both of the grinders (which use 64mm burrs)
were of approximately the same age, about 3.5 years. One of the grinders had
its burr set changed one month before this test was conducted. The other
grinder had run approximately 100 to 150lbs of coffee through it over the
lifespan of its burrs.
There were obvious differences between the espresso machines used in this
study. One was a 1995-vintage semi-automatic Cimbali Junior pourover with a
vibratory pump; the other was a similar automatic rotary pump equipped
Cimbali Junior manufactured in late 2002. Both have identical groups and
heat exchangers, but the boilers (although identically sized) are made
differently. Both machines have been modified with electronic temperature
controls ("PID") in lieu of their original pressurestats. It was necessary
to set both machines up in such a way that they delivered nearly identical
extraction temperature and pressure profiles to eliminate, as much as
possible, the impact of these factors on the taste of the espresso shots
they would produce. This was made a little bit easier by the fact that the
rotary pump machine has been modified [ http://tinyurl.com/299s9v ] with a
pump delay timer, producing "preinfusion" which largely mimics the pressure
ramp up characteristics of a vibratory pump. Extensive adjustment and
testing was done with a Scace thermofilter and handheld datalogger. Graphs
of shot temperatures were obtained and are reproduced below. Both machines
had their extraction pressures adjusted to 9 bar with a portafilter
manometer.
During the course of this experiment, necessary machine maintenance was
performed. This included such things as water backflushing and portafilter
"wiggles" two or three times during the three hour test period, plus a
chemical backflush of both machines after the end of each day's testing.
Every effort was made to adhere as close to practicable to the program of
one set of shot pairs every 7.5 minutes, in order to try to replicate the
temperature stability shown on the Scace device graphs further below. Please
note that the temperature scales displayed are different due to inherent
differences in the shape of the shot temperature curves produced by each
machine. Closer examination of the actual shot temperatures demonstrates
that they are similar.
http://img.photobucket.com/albums/v429/kfoxfoie/S1VibeJuniorFrozenCoffeeTest235pt5.jpg
http://img.photobucket.com/albums/v429/kfoxfoie/D1RotaryJuniorFrozenCoffeeTest231F.jpg
I am indebted to Jim Schulman for his work in designing the way that this
experiment was to be conducted, and for performing the statistical analysis
of the data that was obtained. Originally Jim was to be a taster in this
trial but unfortunately he was only here in spirit and I had to turn to
other friends for the execution of the actual experiment.
The tastings occurred over 4 days with three different tasters. My friends
Bob and Randy both participated in half of the tasting sessions each, and I
participated in all four of them. Bob, has been a friend for two decades and
is a foodie with serious interest in wine. His wife once owned a high end
catering company, and still practices serious cooking at home. They own an
Andreja Premium E61 espresso machine with a commercial Rossi grinder. I have
been supplying them with freshly roasted coffee the last few years. Bob
drinks almost exclusively straight espresso shots, never with sugar and
seldom in milk drinks. I helped them to select their Andreja Premium as a
replacement for a former Bezerra machine, and at the time of purchase
several years ago gave them refresher lessons on proper espresso shot
preparation and shot timing/volume factors. My other friend and assistant,
Randy, does not make home espresso but he is a home coffee roaster using a
Freshroast+. He's often over at my house and has had quite a few espressos
over the years, produced by my machines. When our testing got underway I was
surprised that he was actually able to help me with the machines; turns out
he once dated a barista when he lived in Seattle!
RAW DATA AND STATISTICAL DATA ANALYSIS
Here are some links to data tables and charts that Jim Schulman kindly
provided; they are presented in a much more comprehensible fashion in the
article on home-barista.com and I refer the interested reader to that
article if any of this is unclear:
http://img.photobucket.com/albums/v429/kfoxfoie/kencrema.gif This shows
grading scores on the crema of the paired shots
http://img.photobucket.com/albums/v429/kfoxfoie/kenflavor.gif This shows
grading scores on the intensity of flavor and aroma scores on paired shots
http://img.photobucket.com/albums/v429/kfoxfoie/kenoverall.gif This shows
overall preferences made on the paired shots
Here is a table showing the actual ratings given by the tasters for all 64
shot pairs tasted over 4 days:
FEBRUARY 2007 FROZEN COFFEE vs NEVER FROZEN TEST DATA
DATE 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16
TASTER RA RA RA RA RA RA RA RA KE KE KE KE KE KE KE KE
MACHINE RO VI RO VI RO VI RO VI RO VI RO VI RO VI RO VI
GRINDER NB NB NB NB OB OB OB OB NB NB NB NB OB OB OB OB
COFFEE 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W
OVERALL +1 +1 +1 +2 -1 0 -2 +2 0 -1 +3 +2 -1 +1 +2 -2
CREMA -1 +1 -2 -2 -1 0 +1 -1 -1 +2 +1 +1 -1 0 -1 -1
TASTE +1 +1 +1 +1 -1 0 -1 +2 -1 +1 +2 -1 -2 -1 +1 -2
DATE 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17
TASTER BO BO BO BO BO BO BO BO KE KE KE KE KE KE KE KE
MACHINE RO VI RO VI RO VI RO VI RO VI RO VI RO VI RO VI
GRINDER NB NB NB NB OB OB OB OB NB NB NB NB OB OB OB OB
COFFEE 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W
OVERALL -1 -2 +1 +2 -1 +1 -1 -1 -1 +1 +1 +2 +1 +2 +1 -1
CREMA -1 +1 +1 -1 +1 +1 +1 -1 +2 -2 -1 -1 +1 +1 0 +1
TASTE -1 +1 +1 -2 +1 +1 +1 -1 -1 +2 +1 0 -1 +1 0 -1
DATE 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18
TASTER BO BO BO BO BO BO BO BO KE KE KE KE KE KE KE KE
MACHINE RO VI RO VI RO VI RO VI RO VI RO VI RO VI RO VI
GRINDER NB NB NB NB OB OB OB OB NB NB NB NB OB OB OB OB
COFFEE 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W
OVERALL +2 -1 -2 -1 +1 -1 +1 +1 -2 +1 -1 +1 -1 +2 +1 -1
CREMA +2 -1 -2 -1 -1 -1 +1 +1 +1 0 +2 -1 -1 -1 -2 0
TASTE +2 +1 -1 +2 -1 +1 -1 0 -1 -1 -1 +1 -1 -1 -1 +1
DATE 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19
TASTER RA RA RA RA RA RA RA RA KE KE KE KE KE KE KE KE
MACHINE RO VI RO VI RO VI RO VI RO VI RO VI RO VI RO VI
GRINDER NB NB NB NB OB OB OB OB NB NB NB NB OB OB OB OB
COFFEE 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W 4W 4W 8W 8W
OVERALL -2 -2 0 -1 -2 -2 +1 +1 +1 -1 -1 -2 +1 +2 -1 +2
CREMA -2 0 -1 -1 -1 -2 +1 -1 +1 -1 -2 -1 +1 +2 -1 +1
TASTE -2 -1 0 -1 -2 -2 +1 +1 +1 -1 +1 -2 +1 +2 0 +1
All this data needs to line up to be meaningful, but if you are highly
motivated to do so, have at it! Or, view more readable graphs in the
article on home-barista.com viewable here:
http://www.home-barista.com/store-coffee-in-freezer.html This data is just
the raw data that went into the graphs that are linked to above.
JIM SCHULMAN'S EXPLANATION OF THE FINDINGS AND HIS COMMENTARY ON THEM:
"The test was a sequence of 64 paired shots. One of each pair was fresh
coffee, the other either frozen 4 weeks or 8. The tasters were KEN, Ken,
RAN, randy, and BOB, Bob. Ken tasted 32 pairs, Randy and Bob 16 each. The
tasting was over 4 days. Each pair of shots were done on 2 machines, 2
grinders, and 2 frozen coffees (4 and 8 weeks). The magic number is 8 for
this test, 2*2*2, to capture all the combinations once each. The other magic
number is 40, which would get 5 datapoints into each of the eight bins and
guarantee reliable analyses.
The data is set up as three dependent variables:
OVER: overall preference CREM: which shot has better crema FLAV: which shot
had a more powerful flavor, without judging its quality.
The values of these variables ranges from -3 to 3, with the positive number
always indicating a preference for the frozen coffee.
The data had three independent variables:
COFF: the coffee, either 4 weeks or 8 weeks frozen, compared to the fresh
sample as the control MACH: the machine, vibe or rotary cimbali GRIN: the
grinder, new or older burrs.
Running the analyses of variance for all three variables produced no
significance on either the intercept (a straight overall preference for
fresh or frozen, on any of the three variables, or on any of the 4
interaction effects). If one didn't factor in time or taster, the results
are completely indistinguishable. In fact, if I were looking at these data
from an unknown, I'd be doing cheating chi-squares, since they seem, if
anything, too insignificant -- 8 variables times three regressions, and none
gets close to the 10% k. In this case, I attribute the extra flat outcome
to the mind numbing boredom of tasting nearly identical shots over and over:
lot's of "whatever dude" scores. In any case, this reverse anomaly shows
that any distinction between fresh and frozen was minuscule.
If one does add in the 4 tasting days and 3 tasters as extra variables, one
ends up eating up most of the degrees of freedom with interaction effects.
However, there are some significant results. Randy disliked the 4 week
frozen on the first round, fresh out of the freezer, but liked it on the
fourth day. Ken's preference for the 8 week frozen got less as it aged. Bob
liked the fresh coffee on the rotary with dull burrs the most in both his
trials. These results, along with some even more indescribable ones,
register as statistically significant, but are definitely in the "so what
and who cares" category.
Ken and I discussed the test design since summer 2006. I did some triangle
and 2 of 5 cupping tests of fresh and frozen coffees in order to get some
sense of how to describe the differences and pose the questions. I was able
to pick out the frozen cup or cups from the fresh ones better than chance;
but could get no good verbal handle of how they tasted different. When I did
the same test with two successive fresh roasts, I achieved the same success
rate separating out cups. So my preliminary research found nothing specific
to test or taste for. I had two hypotheses which both got shot down -- that
frozen coffees age faster once unwrapped, and that frozen coffees taste
cartoonish, with missing subtleties. Neither panned out in the least.
Ken's test design reflects this -- it basically shows there is no difference
between fresh and frozen under normal espresso making conditions. Ken never
believed frozen coffee was worse. He designed a test that would have
disproved his belief had a large, or even a minor but systematic, difference
existed.
Now the ball is with the antifreeze people, not to nit pick his results, but
to announce something like "the difference between fresh and frozen is this,
here's how you taste for it, here's how to set up a blind test." Any sort of
"freezing is just bad -- put some vague reason here --" is, after this test,
simply BS. The test moves the debate to the realm of discussing narrow
differences, precisely specified."
FINAL THOUGHTS
Thanks go to my fellow tasters, Bob and Randy, whose buzzed out
participation was essential to the conduct of this study, and to Dan Kehn,
Abe Carmeli, Jeff Sawdy, John Weiss, and Andy Schecter for their editing
assistance.
AND,for the 127th time, I am indebted to Jim Schulman for his efforts in
both experimental design and data analysis. This study could not have been
completed without his assistance.
|
|
| |
Date: 13 Mar 2007 10:23:12
From: rasqual
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
On 9, 10:24 pm, "Ken Fox"
<morceaudemerdeThisMerdeG...@hotmail.com > wrote:
> The material in this post is crossposted with an article covering the same
> research experiment, which appears on the front page of home-barista.com,
> Dan Kehn's super espresso website.
Thank you very much. Although I don't subscribe to the myth myself
(existing studies have shown that temperature is an important staling
variable), your empirical taste testing will be a superb basis for
reassuring folks who remain a bit superstitious. That will be helpful.
Good work, guys!
- Scott
|
| |
Date: 13 Mar 2007 08:11:26
From: Omniryx@gmail.com
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
On 12, 3:41 pm, Neal Reid <NealR...@Nagma.ca > wrote:
> Just to ensure I understand - are you saying that, given no
> baseline, the 'ks' you assigned were quite good?
>
> IIRC there were a couple of "B-"s, which I take your above
> responses to be pretty darn good all things considered.
>
> So if your original reply had said, "blahl blah Control blah B-
> where most experiments get C", would a small flurry have been
> avoided?
Where I failed was in helping people to understand that precise
control of extraneous/confounding variables in a study like this is
impossible, though Dr. Fox and Dr. Schulman certainly tried.
Dr. Fox, quite erroneously, took my observation as a personal
criticism and was affronted by it.
I was criticized, also, for failing to identify these gentlemen with
their appropriate academic credentials.
As to the statistical limitations of their study, I've either made my
point or I haven't. Let us move on.
|
| |
Date: 11 Mar 2007 19:49:00
From: Felix
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Alan (Coffee for Connoisseurs) writes:
> Short term flavour changes in frozen foods are usually
> caused by the formation of ice crystals within the cells
> and the subsequent rupture of cell walls (think frozen &
> defrosted bananas). Reasonably freshly roasted coffee
> doesn't have enough moisture (<7%) for this to be an
> issue. Deep freezing GREEN beans, then thawing and
> roasting, might produce detectable flavour changes
> caused by cell rupture, or at least changes in roasting
> behaviour.
George Howell doesn't mention any difference in roasting behavior when
he describes his company's transition from conventional to freezer
storage of green beans:
http://www.terroircoffee.com/content/view/144/28/
Apparently, some mechanism prevents ice formation from occurring or
altering the bean. Maybe the oils act as a buffer, or the cells are
more robust ... I have no idea.
On the other hand, I have speculated that freezing is controversial
partly because its effectiveness might be correlated with roast level.
Oils that migrate to the surface are no longer protected by the bean's
structure. Freezing might not damage them, but oily beans may require
more careful packaging and thawing, whereas Ken's had "no visible
oiling."
> Reducing the temperature isn't magic, it simply slows
> the reaction rates of all the physical and chemical
> processes taking place inside the coffee.
Refrigeration also slows the reaction rates, and my mixed results may
have reflected the effort I (did not) put into packaging and
acclimating the beans.
Finally, there is one conclusion that nobody seems to have reached:
Ken is very good at reproducing a roast!
Felix
|
| | |
Date: 11 Mar 2007 21:06:33
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Felix" <felixyen@hotmail.com > wrote in message
news:1173667739.922028.249630@c51g2000cwc.googlegroups.com...
>>
> Finally, there is one conclusion that nobody seems to have reached:
> Ken is very good at reproducing a roast!
>
>
> Felix
>
This is going to be very much "roaster-dependent."
My roaster has been heavily modified. It now runs on natural gas (actually
a net negative as the pressure fluctuates during the winter), but it also
has a sorta flow pressure gauge on the input side (which actually measures
backpressure which is why I said "sorta," but it is consistent and allows me
to titrate the heat input), and I've mounted a thermocouple deep into the
drum and can hence montor roast temps in real time.
Plus, this sort of drum roaster has a lot of thermal mass and as a result,
retains heat. It isn't the easiest roaster to "drive," but once you get the
hang of it, it isn't all that hard to pull off very similar roast parameters
roast after roast. In a sense, this roaster "wants" to profile in a certain
way and if you let it, then you can get the same roast, time after time. So
I'd like to take credit for roasting skills but in fact it is as much the
roaster as it is me. My major challenge is dealing with ambient temperature
differences, but after you have been doing that for a while with this
roaster it isn't very difficult.
In a lot of ways, air roasters are much harder to roast consistently with.
ken
|
| |
Date: 11 Mar 2007 15:35:18
From: Omniryx@gmail.com
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
I beg your pardon, Andy. And I beg yours, Dr. Schulman.
I trust that Dr. Fox is now sufficiently mollified.
Dr. Me
|
| | |
Date: 12 Mar 2007 15:41:29
From: Neal Reid
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
In article
<1173652517.908398.256540@h3g2000cwc.googlegroups.com >,
"Omniryx@gmail.com" <Omniryx@gmail.com > wrote:
> I beg your pardon, Andy. And I beg yours, Dr. Schulman.
>
> I trust that Dr. Fox is now sufficiently mollified.
>
> Dr. Me
Just to ensure I understand - are you saying that, given no
baseline, the 'ks' you assigned were quite good?
IIRC there were a couple of "B-"s, which I take your above
responses to be pretty darn good all things considered.
So if your original reply had said, "blahl blah Control blah B-
where most experiments get C", would a small flurry have been
avoided?
--
M for N in address to mail reply
|
| |
Date: 11 Mar 2007 19:03:56
From: Espressopithecus (Java Man)
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
In article <55emnbF24g2fvU1@mid.individual.net >,
morceaudemerdeThisMerdeGoes@hotmail.com says...
> Freezing is controversial, and perhaps moreso with regards to espresso:
>
I have it on good authority that freezers were invented by municipal
engineers intent on delaying the flow of unwanted food to landfills.
This delays expenses in trucking trash and investments in acquisition of
land. Thanks to Ken, we now know freezers provide other benefits! ;-)
But seriously, great work, Ken! Another in a line of excellent articles
inspired by curiosity and modern iconoclasm. I'm thankful once again to
you and Jim.
Cheers,
Rick
|
| |
Date: 11 Mar 2007 11:36:08
From: Omniryx@gmail.com
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Ken Fox snarled:
"Please explain how the extraineous/confounding variables were not
controlled. Differences among the pieces of equipment have been
previously
studied in randomized trials we have published here, and those
differences
were found not significant, with the exception of the grinder burrs
difference which was controlled in the randomization in this trial and
found
also to be "not significant."
When you are dealing with espresso and human beings, the likehood of
ever
pulling off a "perfect experiment," like you might do with a bunch of
rats
in a university experiment, is ZERO; try to do one yourself and come
back
and tell us how it turned out.
It was a completely balanced design with other factors offset,
designed in
from long before the test was performed, and taken into consideration
both
during the performance of the test and statistically. This table with
actual statistical results was not put into the article as
"published,"
however I am going to paste it in here for anyone interested in
statistics."
Relax, Ken, the grades were for the experiment, not the
experimenters. Your 4.0 is intact.
You identify above precisely why the error in studies like this cannot
be made wholly stochastic. It simply is not possible to control
them. It certainly isn't that you didn't try.
Glancing at my CV, I note that I have conducted something in excess of
forty experimental studies with human beings. In none of them did the
control of extraneous/confounding variables rise above the grade I
assigned to your study. So, you see, your hissing little "try one
yourself" is scarcely applicable. As a researcher, a teacher of
research, an IRB member at two major universities, a research
consultant for the Rand Corporation and the Wharton School of
Business, and a former reviewer of multi-million dollar NIH RO1
grants, I'm in a pretty fair position to comment.
Had you not been so quick to take umbrage, you might have realized
that my scoring reflected the excellent effort that you and Andy put
into your work. Work which, alas, is inherently impossible to study
with strict controls. You just have to be as careful as possible and
be content with that. That's why most journals expect that
experimental research reports will include a statement of assumptions
and limitations.
Don't let your temper shoot from the hip, Ken.
Will
(He may not know coffee but he does know research methods.)
|
| | |
Date: 11 Mar 2007 15:52:53
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
<Omniryx@gmail.com > wrote in message
news:1173638168.061242.45870@n33g2000cwc.googlegroups.com...
> >
> Don't let your temper shoot from the hip, Ken.
>
> Will
> (He may not know coffee but he does know research methods.)
>
I might have phrased your comment differently, Will ----
ken
|
| | |
Date: 11 Mar 2007 15:01:27
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Omniryx@gmail.com wrote:
> my scoring reflected the excellent effort that you and Andy put
> into your work.
Ken and JIM. Actually, Dr. Fox and DOCTOR Schulman.
BTW, congrats, Jim! Maybe now Petracco will return your emails! :-)
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| |
Date: 11 Mar 2007 06:33:33
From: James Hoffmann
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
On 11, 1:21 pm, Andy Schecter
<schec...@remove.me.rochester.rr.com > wrote:
> gscace wrote:
> > What Ken and Jim have
> > done is shoot down another coffee myth. Way to go!
>
> I agree 100% that this was an excellent study and I join you in congratulating
> Ken and Jim. I don't join those who assert that the case is closed, however.
> 1. How low does the temperature have to be to achieve good preservation?
> 2. How long can the coffee be held without ill effects? 8 weeks, 16 weeks, 52
> weeks?
>
> > Actually, a whole lot of chemical reactions are exponential functions
> > of temperature. It would seem obvious to anyone schooled in the art
> > of chemistry (like anyone who paid attention in second semester
> > freshman chemistry in college), that a very good way to reduce staling
> > is to just lower the storage temperature.
>
> Perhaps the opposite side of the issue is more interesting. When espresso
> coffee is extremely fresh, it doesn't extract well. So it is common to have to
> wait 3-5 days before using it. Will storing the freshly-roasted coffee at
> slightly elevated temperatures (say, 90F) decrease the necessary resting time?
>
> --
>
> -Andy S.
>
> http://www.flickr.com/photos/andy_s/sets/
I guess it probably would but it would be a much shorter time window
where it is any good before you completely ruin it.
|
| | |
Date: 11 Mar 2007 12:01:53
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
James Hoffmann wrote:
> I guess it probably would but it would be a much shorter time window
> where it is any good before you completely ruin it.
James, I'm sure you've been in the situation where you realize you won't have
enough "rested" coffee on hand for the next day's coffee making. Would holding
the somewhat "green" coffee at 90F for 12 hours or 24 hours make an improvement?
I'm not suggesting holding it indefinitely at a high temp.
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| | | |
Date: 11 Mar 2007 11:17:06
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Andy Schecter" <schecter@remove.me.rochester.rr.com > wrote in message
news:45f427d8$0$4893$4c368faf@roadrunner.com...
> James Hoffmann wrote:
>> I guess it probably would but it would be a much shorter time window
>> where it is any good before you completely ruin it.
>
> James, I'm sure you've been in the situation where you realize you won't
> have enough "rested" coffee on hand for the next day's coffee making.
> Would holding the somewhat "green" coffee at 90F for 12 hours or 24 hours
> make an improvement?
>
> I'm not suggesting holding it indefinitely at a high temp.
>
>
> --
>
>
> -Andy S.
>
> http://www.flickr.com/photos/andy_s/sets/
Andy,
Why go at it half-assed?
Don't you have a kiln somewhere in the area?
ken
|
| | | | |
Date: 11 Mar 2007 13:38:50
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Ken Fox wrote:
> Why go at it half-assed?
>
> Don't you have a kiln somewhere in the area?
You're making a joke out of it, while I'm asking a reasonably serious question.
When you calm down from your giddiness, feel free to post a considered reply. :-)
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| | | | | |
Date: 11 Mar 2007 12:36:57
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Andy Schecter" <schecter@remove.me.rochester.rr.com > wrote in message
news:45f43e90$0$4895$4c368faf@roadrunner.com...
> Ken Fox wrote:
>> Why go at it half-assed?
>>
>> Don't you have a kiln somewhere in the area?
>
>
> You're making a joke out of it, while I'm asking a reasonably serious
> question.
>
> When you calm down from your giddiness, feel free to post a considered
> reply. :-)
>
> --
>
>
> -Andy S.
>
> http://www.flickr.com/photos/andy_s/sets/
ok, a kiln might be a little too hot. How about next to the furnace?
ken
;-)
|
| |
Date: 11 Mar 2007 05:48:49
From: gscace
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
On 11, 12:29 am, "Ken Fox" <morceaudemerdeSnipT...@hotmail.com >
wrote:
> "gscace" <gregory.sc...@nist.gov> wrote in message
>
> news:1173588462.908635.223970@s48g2000cws.googlegroups.com...
>
>
>
> > On 10, 8:15 pm, "Dan Bollinger" <danNObollin...@insightSPAMbb.com>
> > wrote:
> >> Great stuff, Ken, Jim and all. A major contribution to the art.
>
> >> When I hear 'frozen in a very cold freezer within an hour of roasting,'
> >> it
> >> reminds me of 'flash freezing' that is done on other foodstuffs, also
> >> with
> >> benefit. I suspect that such techniques are ultimately what your work is
> >> pointing toward. Dan
>
> > Actually, a whole lot of chemical reactions are exponential functions
> > of temperature. It would seem obvious to anyone schooled in the art
> > of chemistry (like anyone who paid attention in second semester
> > freshman chemistry in college), that a very good way to reduce staling
> > is to just lower the storage temperature. Folks like to ascribe
> > magical powers to coffee and they won't use their senses and
> > experience to question coffee religion dogma. What Ken and Jim have
> > done is shoot down another coffee myth. Way to go!
>
> > -Greg
>
> The funny thing is that over the years I've talked off the cuff with a whole
> bunch of people, I think including you, Greg, about freezing. Seems like
> most everyone I talked to was doing it, if not all the time, certainly on
> occasion, and found that it worked for them just fine.
>
> Yet there was always this myth out there about how awful it was to do it,
> for a whole bunch of reasons that never had any logic or sense to them. It
> was "ludicrous" or somesuch; forgot who used that word:-) But we did it
> (freezing) anyway and it worked for us.
>
> You have a fairly similar roasting situation to mine; I'm assuming that
> firing up your Has Garanti for a single batch just doesn't make sense most
> of the time.
>
> Now we just need to get some of those other myths busted.
>
> ken
Yeah, I've been freezing coffee for a long time. As you say it takes
an hour and a quarter to roast 1 kg, and it takes 2 hours to roast
3. I use a canning jar and when I need to refill a grinder I take
the jar out of the freezer, let it warm to room temp, and dump da
contents into the hopper.
|
| | |
Date: 12 Mar 2007 16:48:56
From: Brent
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Hint Greg - don't bake the beans, run the Has a little hotter, the roast
times hsould drop then as well....
:)
Brnet
As you say it takes
> an hour and a quarter to roast 1 kg, and it takes 2 hours to roast
> 3.
|
| |
Date: 10 Mar 2007 20:47:43
From: gscace
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
On 10, 8:15 pm, "Dan Bollinger" <danNObollin...@insightSPAMbb.com >
wrote:
> Great stuff, Ken, Jim and all. A major contribution to the art.
>
> When I hear 'frozen in a very cold freezer within an hour of roasting,' it
> reminds me of 'flash freezing' that is done on other foodstuffs, also with
> benefit. I suspect that such techniques are ultimately what your work is
> pointing toward. Dan
Actually, a whole lot of chemical reactions are exponential functions
of temperature. It would seem obvious to anyone schooled in the art
of chemistry (like anyone who paid attention in second semester
freshman chemistry in college), that a very good way to reduce staling
is to just lower the storage temperature. Folks like to ascribe
magical powers to coffee and they won't use their senses and
experience to question coffee religion dogma. What Ken and Jim have
done is shoot down another coffee myth. Way to go!
-Greg
|
| | |
Date: 11 Mar 2007 09:21:16
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
gscace wrote:
> What Ken and Jim have
> done is shoot down another coffee myth. Way to go!
I agree 100% that this was an excellent study and I join you in congratulating
Ken and Jim. I don't join those who assert that the case is closed, however.
1. How low does the temperature have to be to achieve good preservation?
2. How long can the coffee be held without ill effects? 8 weeks, 16 weeks, 52
weeks?
> Actually, a whole lot of chemical reactions are exponential functions
> of temperature. It would seem obvious to anyone schooled in the art
> of chemistry (like anyone who paid attention in second semester
> freshman chemistry in college), that a very good way to reduce staling
> is to just lower the storage temperature.
Perhaps the opposite side of the issue is more interesting. When espresso
coffee is extremely fresh, it doesn't extract well. So it is common to have to
wait 3-5 days before using it. Will storing the freshly-roasted coffee at
slightly elevated temperatures (say, 90F) decrease the necessary resting time?
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| | |
Date: 10 Mar 2007 22:29:20
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"gscace" <gregory.scace@nist.gov > wrote in message
news:1173588462.908635.223970@s48g2000cws.googlegroups.com...
> On 10, 8:15 pm, "Dan Bollinger" <danNObollin...@insightSPAMbb.com>
> wrote:
>> Great stuff, Ken, Jim and all. A major contribution to the art.
>>
>> When I hear 'frozen in a very cold freezer within an hour of roasting,'
>> it
>> reminds me of 'flash freezing' that is done on other foodstuffs, also
>> with
>> benefit. I suspect that such techniques are ultimately what your work is
>> pointing toward. Dan
>
> Actually, a whole lot of chemical reactions are exponential functions
> of temperature. It would seem obvious to anyone schooled in the art
> of chemistry (like anyone who paid attention in second semester
> freshman chemistry in college), that a very good way to reduce staling
> is to just lower the storage temperature. Folks like to ascribe
> magical powers to coffee and they won't use their senses and
> experience to question coffee religion dogma. What Ken and Jim have
> done is shoot down another coffee myth. Way to go!
>
> -Greg
>
The funny thing is that over the years I've talked off the cuff with a whole
bunch of people, I think including you, Greg, about freezing. Seems like
most everyone I talked to was doing it, if not all the time, certainly on
occasion, and found that it worked for them just fine.
Yet there was always this myth out there about how awful it was to do it,
for a whole bunch of reasons that never had any logic or sense to them. It
was "ludicrous" or somesuch; forgot who used that word:-) But we did it
(freezing) anyway and it worked for us.
You have a fairly similar roasting situation to mine; I'm assuming that
firing up your Has Garanti for a single batch just doesn't make sense most
of the time.
Now we just need to get some of those other myths busted.
ken
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| | | |
Date: 11 Mar 2007 09:12:38
From: Dan Bollinger
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
> Yet there was always this myth out there about how awful [freezing] was to do
Ken, I'll make a correction here. It is a pet peeve of mine, so feel free to
ignore. A myth is a story passed down from one generation to another having a
'grain of truth' at its core, hence its value in sharing and repeating. Before
the advent of books, it was used to transmit learning to the next generation.
Not unlike parables and proverbs do. So, we can't really use the word myth here
because it is less than one generation old, and has no grain of truth. "Freezing
coffee is bad" is more accurately labeled a falsehood, plain and simple. No
reason to elevate this igrnorance to mythical status.
End of rant, Dan
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| | | | |
Date: 11 Mar 2007 12:18:17
From: Dave S
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Dan Bollinger wrote:
>> Yet there was always this myth out there about how awful [freezing]
>> was to do
> "Freezing
> coffee is bad" is more accurately labeled a falsehood, plain and simple.
> No reason to elevate this igrnorance to mythical status.
You use the phrase "falsehood, plain and simple" to talk about the
phrase "Freezing coffee is bad". Ken has only shown that to be true for
very specific circumstances.
The question of whether or not to freeze coffee most frequently arises
(to me at least) when people find out that I have some interest in
coffee, and have done some reading and practicing. Then they will ask,
"Should I keep my coffee in the freezer?". The right answer to that
question is more than a "plain and simple" 'NO'.
Dave S.
P.S. I understand that you wrote to educate the list about the word
"myth", and that I am writing about a different subject.
|
| |
Date: 10 Mar 2007 20:38:37
From: gscace
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
On 10, 6:28 pm, r...@math.hawaii.NOSPAM.edu (D. Ross) wrote:
> "Ken Fox" <morceaudemerdeThisMerdeG...@hotmail.com> wrote:
>
>
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| |
Date: 10 Mar 2007 20:15:13
From: Dan Bollinger
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Great stuff, Ken, Jim and all. A major contribution to the art.
When I hear 'frozen in a very cold freezer within an hour of roasting,' it
reminds me of 'flash freezing' that is done on other foodstuffs, also with
benefit. I suspect that such techniques are ultimately what your work is
pointing toward. Dan
|
| |
Date: 10 Mar 2007 09:29:19
From: Randy G.
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Ken Fox" <morceaudemerdeThisMerdeGoes@hotmail.com > wrote:
>The material in this post is crossposted with an article covering the same
>research experiment, which appears on the front page of home-barista.com,
>Dan Kehn's super espresso website. This post is not a complete word for
>word copy of the home-barista.com article, but rather is presented in a
>somewhat more "usenet-friendly" manner without some of the content that
>makes the web published article more like a "magazine article." The web
>article, which can be found here
>http://www.home-barista.com/store-coffee-in-freezer.html
>
A couple of comments. First, what an impressive experiment which
should put an end to any reasonable doubt as to the value of freezing
freshly-roasted coffee over a short term. It would be interesting to
duplicate this using a home freezer section of the fridge to see if
there is any benefit to those temperatures since that is the equipment
most people have for freezing.
The second comment is, I am not the Randy in the story- mentioning
this just to help lend more credence to the data.. ;-)
Randy " 'Hey! It's cold in here,' said the bean." G.
http://www.EspressoMyEspresso.com
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| | |
Date: 10 Mar 2007 21:38:10
From: D. Ross
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Randy G. <frcn@DESPAMMOcncnet.com > wrote:
|
| | | |
Date: 10 Mar 2007 15:00:07
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"D. Ross" <ross@math.hawaii.NOSPAM.edu > wrote in message
news:45f323e4.7554873@localhost...
> Randy G. <frcn@DESPAMMOcncnet.com> wrote:
>
>
|
| | | | |
Date: 10 Mar 2007 23:28:26
From: D. Ross
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Ken Fox" <morceaudemerdeThisMerdeGoes@hotmail.com > wrote:
|
| | | | | |
Date: 10 Mar 2007 18:09:12
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"D. Ross" <ross@math.hawaii.NOSPAM.edu > wrote in message
news:45f33dc9.14184225@localhost...
> "Ken Fox" <morceaudemerdeThisMerdeGoes@hotmail.com> wrote:
>
>
|
| | | | | | |
Date: 10 Mar 2007 21:56:11
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Ken Fox wrote:
> I'd be surprised if the industry would have any interest because the ket
> for truly fresh coffee is pretty small and the likelihood of superkets
> devoting freezer shelf space to coffee seems prettly slim to me.
Well, for one, there are possible patent issues:
http://tinyurl.com/2m2hev
http://www.sivetzcoffee.com/preservation_patent.htm
Also, the first patent (listed in the tiny.url above) states that the coffee
must be held below -17C for satisfactory preservation. Minus 17C is about 1F.
Not everyone's home freezer can do this.
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| | | | | | | |
Date: 11 Mar 2007 00:16:37
From: Steve Ackman
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
In <45f36fb3$0$16660$4c368faf@roadrunner.com >, on Sat, 10 2007
21:56:11 -0500, Andy Schecter wrote:
> Well, for one, there are possible patent issues:
> http://tinyurl.com/2m2hev
> http://www.sivetzcoffee.com/preservation_patent.htm
>
> Also, the first patent (listed in the tiny.url above) states that the coffee
> must be held below -17C for satisfactory preservation. Minus 17C is about 1F.
> Not everyone's home freezer can do this.
The "standard" for home freezers is to be able to
attain at least 0°F. I'd be very surprised if 2% of
freezers in the US were incapable of that. Certainly
every freezer we've ever owned could get below zero.
When I did my coffee freezing "observation," it was
in a side-by-side at -7°F. which was just below mid-
scale of the freezer thermostat... which in large part
is why we bought that same model, though with
different skin, for this house.
|
| | | | | | | | |
Date: 11 Mar 2007 09:26:10
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Steve Ackman wrote:
> The "standard" for home freezers is to be able to
> attain at least 0=B0F. I'd be very surprised if 2% of=20
> freezers in the US were incapable of that. Certainly
> every freezer we've ever owned could get below zero.
I'm not sure if you're referring to stand-alone freezers or simply to the=
=20
freezer section of combination units. Certainly in my younger days I live=
d in=20
apartments where the freezer section of the combo unit barely kept ice cr=
eam=20
solid (around 20F?). Also, the regular warming cycles required for automa=
tic=20
defrost may have a detrimental effect.
--=20
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
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| | | | | | | | | |
Date: 11 Mar 2007 22:49:29
From: Steve Ackman
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
In <45f40364$0$8968$4c368faf@roadrunner.com >, on Sun, 11 2007
09:26:10 -0400, Andy Schecter wrote:
> Steve Ackman wrote:
>> The "standard" for home freezers is to be able to
>> attain at least 0°F. I'd be very surprised if 2% of
>> freezers in the US were incapable of that. Certainly
>> every freezer we've ever owned could get below zero.
>
> I'm not sure if you're referring to stand-alone freezers or simply to the
> freezer section of combination units.
Either. Standard food safety recommends setting your
freezer to 0°F. It would be kind of tough to make that
recommendation if home freezers normally can't attain
that.
I just checked our side-by-side. -8.7°F on the
bottom shelf, -13.4°F on the top shelf with the
compressor and fan running. Both will get lower
until the thermostat kicks off, but once it's been
off awhile, the top shelf will warm to ~10°F above
the bottom shelf. (Thermostat is ked 1-9 with 9
being coldest. This is on 7.)
> Certainly in my younger days I lived in
> apartments where the freezer section of the combo unit barely kept ice cream
> solid (around 20F?).
Gasket worn or torn, door misaligned, or some other
mechanical problem? We've owned/used at least a couple
dozen refrigerator freezer compartments, and none was
ever guilty of such dairy neglect. ;-)
> Also, the regular warming cycles required for automatic
> defrost may have a detrimental effect.
I'd need a datalogger or 3 or 4 to see what's going
on in our freezer, but our ice cream never gets soft,
and since I rotate our "emergency coffee" out of the
freezer every couple weeks, whatever the temperature
dynamics are, they just don't seem to have any effect
on anything as far we can taste.
|
| | | | | | | | | | |
Date: 12 Mar 2007 10:18:34
From: Bill (Adopt)
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
In article <slrnev9ftp.fm0.steve@wizard.dyndns.org >,
Steve Ackman <steve@SNIP-THIS.twoloonscoffee.com > wrote:
> In <45f40364$0$8968$4c368faf@roadrunner.com>, on Sun, 11 2007
> 09:26:10 -0400, Andy Schecter wrote:
> > Steve Ackman wrote:
[..]
> > Certainly in my younger days I lived in
> > apartments where the freezer section of the combo unit
> > barely kept ice cream
> > solid (around 20F?).
> Gasket worn or torn, door misaligned, or some other
> mechanical problem? We've owned/used at least a couple
> dozen refrigerator freezer compartments, and none was
> ever guilty of such dairy neglect. ;-)
> > Also, the regular warming cycles required for automatic
> > defrost may have a detrimental effect.
> I'd need a datalogger or 3 or 4 to see what's going
> on in our freezer, but our ice cream never gets soft,
> and since I rotate our "emergency coffee" out of the
> freezer every couple weeks, whatever the temperature
> dynamics are, they just don't seem to have any effect
> on anything as far we can taste.
I think in reality your last note might thankfully be
most people's experience, providing their appliance is
in acceptable condition...
The reason that the rather dumb thermostats continue
to be used in appliances - and also work well in keeping
'frost free' freezers at their rated long-term storage
temperature even though they require an intermittent
heating circuit within the evaporator to function - is
that throughout the freezer's cycling, the core temp of
the frozen goods should be consistently maintained at
or below the rated claim of the appliance.
If the thernostats don't maintain the core temperature
of the stored goods, then that freezer would be useless
for long-term storage - and Health and Safetey Regs,
(or Fed. Regs in the USofA) would not allow the unit to
be sold with any kind of a claim, if sold at all...
The normal cyclic variations in freezer temperature
should not affect the actual core temperature of any
stored goods including coffee 'beans', which should
continue to be maintained at or below to the rated
storage claim of the appliance...
I guess the sun is occasionally allowed to shine, even
in polar regions... ;))
Bill ZFC
--
Adoption InterLink UK with -=- http://www.billsimpson.com/
Domain Host Orpheus Internet -=- http://www.orpheusinternet.co.uk/
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Date: 11 Mar 2007 11:25:25
From: Jack Denver
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
I have a 2nd fridge in my basement that is an ordinary top freezer self
defrosting type (Whirlpool). After an unfortunate episode involving its
predecessor and a bad compressor and a lot of spoiled food, I got a little
electronic thermometer that stores hi-low readings and has an alarm (I
highly recommend this device which cost me maybe $15). If I keep the fridge
section set at around 36 to 38 (which is where it should be) the freezer
compartment goes from around -5F (at the end of a compressor cycle) to as
high as 10F (during autodefrost or when the door is opened). Most fridges
have no thermostat in the freezer compartment - their freezer temp is a side
effect of the temp in the fridge where the thermostat is. Even the ones that
have "controls" for the freezer are just usually controlling a baffle that
controls the amount of cold air diverted from the freezer to the fridge.
The exceptions are high end things like SubZeros that have independent
compressors for both sections but you pay dearly for those (especially
given, as Ken said, that costco will sell you a freezer that is just as cold
for $200).
If you want less variation and a colder temp you should get a chest type
freezer (no fridge) as Ken suggested. The freezer sections of most home
fridges are not ideal freezers.
"Andy Schecter" <schecter@remove.me.rochester.rr.com > wrote in message
news:45f40364$0$8968$4c368faf@roadrunner.com...
Steve Ackman wrote:
> The "standard" for home freezers is to be able to
> attain at least 0°F. I'd be very surprised if 2% of freezers in the US
> were incapable of that. Certainly
> every freezer we've ever owned could get below zero.
I'm not sure if you're referring to stand-alone freezers or simply to the
freezer section of combination units. Certainly in my younger days I lived
in
apartments where the freezer section of the combo unit barely kept ice cream
solid (around 20F?). Also, the regular warming cycles required for automatic
defrost may have a detrimental effect.
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| | | | | | | | | | |
Date: 11 Mar 2007 12:06:36
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Jack Denver wrote:
> If you want less variation and a colder temp you should get a chest type
> freezer (no fridge) as Ken suggested. The freezer sections of most home
> fridges are not ideal freezers.
Some people have reported poor results with freezing their roasted beans.
Despite what some people are now saying, Ken's study didn't prove these people
are deluded. Perhaps their packages weren't properly sealed, perhaps their
freezers weren't cold enough, or perhaps they held the coffee in their freezer
too long.
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
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Date: 11 Mar 2007 12:46:20
From: Dan Bollinger
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
> Some people have reported poor results with freezing their roasted beans.
>
> Ken's study didn't prove these people are deluded.
Actually, it very well may have. If they didn't test using blind or
double-blind testing procedures you can't rule out observer, or in this case
taster's, bias. After all they weren't experiments, but anecdotal reports. And
we all know what they say about people having opinions, everyone's got one.
Dan
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| | | | | | | | | | | | |
Date: 11 Mar 2007 11:16:09
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Dan Bollinger" <danNObollinger@insightSPAMbb.com > wrote in message
news:XvednVq-Go_Dr2nYnZ2dnUVZ_syunZ2d@insightbb.com...
>> Some people have reported poor results with freezing their roasted beans.
>>
>> Ken's study didn't prove these people are deluded.
>
> Actually, it very well may have. If they didn't test using blind or
> double-blind testing procedures you can't rule out observer, or in this
> case taster's, bias. After all they weren't experiments, but anecdotal
> reports. And we all know what they say about people having opinions,
> everyone's got one.
>
> Dan
I wouldn't use the word "deluded," but here is a short list of coffee
related things I have "convinced" myself of, at one time or another, only to
be shown wrong by my own blind tasting:
(1) rotary pump machines make better coffee than vibratory pump machines
(2) new grinder burrs are superior to partially used ones (at way below
rated service life) when it comes to espresso produced
(3) freezing might damage coffee
(4) Pre-infusion is a waste of time and effort in rotary pump machines
ken
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Date: 11 Mar 2007 03:58:53
From: D. Ross
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
|
| | | | | | | | |
Date: 10 Mar 2007 23:45:26
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
D. Ross wrote:
> Well, since Ken's temps were higher than this he *clearly* didn't infringe.
No, his temps were lower, -26C, so he's clearly in deep doodoo: patent
violation, conspiracy to commit patent violation, and conspiracy to incite
minors to commit patent violations without parental consent.
District Attorney Nifong is preparing the indictment as we speak. :-0
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| | | | | | | |
Date: 10 Mar 2007 20:06:53
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Andy Schecter" <schecter@remove.me.rochester.rr.com > wrote in message
news:45f36fb3$0$16660$4c368faf@roadrunner.com...
> Ken Fox wrote:
>> I'd be surprised if the industry would have any interest because the
>> ket for truly fresh coffee is pretty small and the likelihood of
>> superkets devoting freezer shelf space to coffee seems prettly slim to
>> me.
>
> Well, for one, there are possible patent issues:
> http://tinyurl.com/2m2hev
> http://www.sivetzcoffee.com/preservation_patent.htm
>
> Also, the first patent (listed in the tiny.url above) states that the
> coffee must be held below -17C for satisfactory preservation. Minus 17C is
> about 1F. Not everyone's home freezer can do this.
>
> --
>
>
> -Andy S.
>
> http://www.flickr.com/photos/andy_s/sets/
just visit your neighborhood Costco. They'll sell you a 7 cubic foot
Kirkland Signature (Whirlpool) chest freezer for less than $200, that is
identical to the two that I own.
Are you implying that I am infringing on patents by storing coffee in my
Costco freezer? Where do I send the royalties?
ken
;-)
|
| | | | | | | | |
Date: 10 Mar 2007 22:54:49
From: Andy Schecter
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Ken Fox wrote:
> Are you implying that I am infringing on patents by storing coffee in my
> Costco freezer?
Exactly. You are in a whole heap of trouble, Dr. Fox.
> Where do I send the royalties?
Send the royalties to me, rest assured that I will store them below -17C in my
brand new Costco freezer.
--
-Andy S.
http://www.flickr.com/photos/andy_s/sets/
|
| | | | | | |
Date: 11 Mar 2007 02:53:07
From: D. Ross
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Ken Fox" <morceaudemerdeThisMerdeGoes@hotmail.com > wrote:
|
| | | | | | | |
Date: 10 Mar 2007 20:04:40
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
D. Ross" <ross@math.hawaii.NOSPAM.edu > wrote in message
news:45f36c5a.26105537@localhost...
>>
>
|
| | | | | | | | |
Date: 11 Mar 2007 04:02:49
From: D. Ross
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
|
| | | | | |
Date: 11 Mar 2007 00:33:42
From: Coffee for Connoisseurs
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Excellent work, Ken. Totally compliant with the physics and chemistry of
roasted coffee, and validates my own experience.
>there would probably be a bit more interest in the
>slightly different study you didn't do, as to whether beans a few days off
>roast (ie, as you would get them mail order) are preserved for at least a
>few weeks by freezing.
The answer to that one is another "of course it does". Reducing the
temperature isn't magic, it simply slows the reaction rates of all the
physical and chemical processes taking place inside the coffee. Short term
flavour changes in frozen foods are usually caused by the formation of ice
crystals within the cells and the subsequent rupture of cell walls (think
frozen & defrosted bananas). Reasonably freshly roasted coffee doesn't have
enough moisture (<7%) for this to be an issue. Deep freezing GREEN beans,
then thawing and roasting, might produce detectable flavour changes caused
by cell rupture, or at least changes in roasting behaviour.
Coffee frozen a week after roasting would still taste a week old when
thawed.
--
Alan
alanfrew@coffeeco.com.au
www.coffeeco.com.au
|
| | | | | | |
Date: 10 Mar 2007 18:14:36
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
"Coffee for Connoisseurs" <alanfrew@coffeeco.com.au > wrote in message
news:G7IIh.9586$8U4.3616@news-server.bigpond.net.au...
> Excellent work, Ken. Totally compliant with the physics and chemistry of
> roasted coffee, and validates my own experience.
>
>>there would probably be a bit more interest in the
>>slightly different study you didn't do, as to whether beans a few days off
>>roast (ie, as you would get them mail order) are preserved for at least a
>>few weeks by freezing.
>
> The answer to that one is another "of course it does". Reducing the
> temperature isn't magic, it simply slows the reaction rates of all the
> physical and chemical processes taking place inside the coffee. Short term
> flavour changes in frozen foods are usually caused by the formation of ice
> crystals within the cells and the subsequent rupture of cell walls (think
> frozen & defrosted bananas). Reasonably freshly roasted coffee doesn't
> have enough moisture (<7%) for this to be an issue. Deep freezing GREEN
> beans, then thawing and roasting, might produce detectable flavour changes
> caused by cell rupture, or at least changes in roasting behaviour.
>
> Coffee frozen a week after roasting would still taste a week old when
> thawed.
>
>
> --
> Alan
>
> alanfrew@coffeeco.com.au
> www.coffeeco.com.au
>
>
>
Thank you, Alan.
The funny thing to me is that if you asked most anyone you know who knows
little about coffee, whether freezing would prolong shelf life and whether
freezing would damage coffee, they would look at you like you were a tian
or were really dumb and had just asked some really stupid questions. I've
never asked her but my cleaning lady, someone with enough common sense for 2
people, would amost certainly have that reaction and would have assumed,
forever, that freezing coffee was a good way to keep it fresh for a longer
period of time.
Like most hobbies and interests, coffee collects its myths from its
admirers. And this anti-coffee-freezing mythology has been propogated by a
great many people over a long period of time. Hopefully this study will
encourage other people to test some of the remaining coffee myths out there
that could use debunking.
ken
|
| | |
Date: 10 Mar 2007 21:38:52
From: D. Ross
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Randy G. <frcn@DESPAMMOcncnet.com > wrote:
|
| | | |
Date: 10 Mar 2007 23:31:16
From: D. Ross
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
Sorry about the duplicate post - my system (which amalgamates from several
Usenet servers) has developed some kinks.
- David R.
--
Less information than you ever thought possible:
http://www.demitasse.net
|
| |
Date: 10 Mar 2007 05:41:18
From: Omniryx@gmail.com
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
For willingness to undertake a time-consuming study....A
For motivation and enthusiasm....A
For understanding of appropriate research methods....A-
For acceptable control of extraneous/confounding variables....B-
But perhaps that is about the best that can be done with the equipment
you have at hand, so I commend you on a nice job.
|
| | |
Date: 10 Mar 2007 07:57:39
From: Ken Fox
Subject: Re: Freezing Coffee Used for Espresso; a Randomized Trial
|
<Omniryx@gmail.com > wrote in message
news:1173534078.561551.99550@c51g2000cwc.googlegroups.com...
> For willingness to undertake a time-consuming study....A
> For motivation and enthusiasm....A
> For understanding of appropriate research methods....A-
> For acceptable control of extraneous/confounding variables....B-
>
> But perhaps that is about the best that can be done with the equipment
> you have at hand, so I commend you on a nice job.
>
Please explain how the extraineous/confounding variables were not
controlled. Differences among the pieces of equipment have been previously
studied in randomized trials we have published here, and those differences
were found not significant, with the exception of the grinder burrs
difference which was controlled in the randomization in this trial and found
also to be "not significant."
When you are dealing with espresso and human beings, the likehood of ever
pulling off a "perfect experiment," like you might do with a bunch of rats
in a university experiment, is ZERO; try to do one yourself and come back
and tell us how it turned out.
It was a completely balanced design with other factors offset, designed in
from long before the test was performed, and taken into consideration both
during the performance of the test and statistically. This table with
actual statistical results was not put into the article as "published,"
however I am going to paste it in here for anyone interested in statistics.
ken
p.s. this is the work of Jim Schulman, who deserves credit for the
experimental design and analysis
OVERALL:
lm(formula = over ~ coff * I(date - 17.5) * tast * grin * mach)
Residuals:
Min 1Q Median 3Q Max
-1.600e+00 -2.500e-02 -2.421e-17 2.500e-02 1.200e+00
Coefficients:
Estimate Std. Error t value
Pr(>
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