Article Feedback: Coffee: To Freeze or Not to Freeze?

Offer your ideas on how to improve the site or report problems.
Ken Fox

#1: Post by Ken Fox »

Here's your chance to critique the article, supplement it with your own experiences, or suggest further research on this topic (not that I'd be up for it, but maybe someone else would be :roll: )

For access to the article content, click below:

Read more...

ken
What, me worry?

Alfred E. Neuman, 1955

User avatar
RapidCoffee
Team HB

#2: Post by RapidCoffee »

He's baaaack.... and with a bang! Great article, Ken, and nice to see you back on H-B.
John

Rainman

#3: Post by Rainman »

Wow! nicely done, Ken- if I didn't know any better, I'd swear you've had experience doing drug studies in the past. Good transparent methodology, BUT- it's just one study, and it would be great if someone else could repeat it and find the same results. One silly question- can you post your roast curve? I'm wondering what sort of temp ramp you did (especially up to and through 1st crack- looks like it was pretty quick, but you still got a nice FC+ roast?

Nice "myth-busting" btw!

Ray
LMWDP #18

Ken Fox

#4: Post by Ken Fox » replying to Rainman »

I actually have a research background in my distant past, having published articles in (the now supplanted) American Journal of Physiology, as a college student, and in the Journal of Clinical Oncology and International Journal of Radiation Oncology, Biology, and Physics when I was in post graduate training and in practice as a physician. Jim Schulman, who came up with the experimental design and who did the data analysis, has recently obtained a ph.D in Sociology at the University of Chicago. So both of us have experience in experimental design and statistics.

I have cobbled together an idealized roast curve which is reproduced here:

Image

I am calling it idealized because although I roast with the aid of a rigid thermocouple mounted in the drum of my roaster, along with a fluke datalogger, I haven't datalogged any roasts in 6 or more months. The only change I've made in my roast technique since the previous datalogged roasts is that I let the drum cool down slightly more before introducing the beans, although it was always under a real temperature of 380F.

I have taken my last set of logged roasts, which were logged every 20 seconds, and instead taken the first number and every 3rd measurement thereafter, which corresponds to one measurement every minute after "charging" the roaster. I think this makes the graph more easily understood since otherwise I'd have to explain that each data point was taken at 20 second intervals.

[EDIT: I made a data transcription error in constructing the first graph I put in this post, which I have just corrected. If you saw this post in the last hour, I apologize for any confusion I may have caused you]

I have years of experience with this roaster at this point and have gotten a lot of feedback from both professionals and serious amateurs on roast samples I've sent out. The type of roaster I am using is well known in the professional roasting community, and I have had several comments over the years that this type of roaster produces its best roasts when the roast is completed fairly quickly, with considerably poorer results if the roasts are extended out beyond 14 minutes (the coffee tends towards "flatness" with that sort of roast profile in this roaster). Earlier on I used to extend my roasts out much longer and the results were in fact, inferior to what I get now.

Finally, it is really hard if not impossible to extrapolate roast profiles from one roaster to another, and what works well on my drum might work very poorly in another roaster; you just have to experiment to find what works best in any particular roasting setup.

ken
What, me worry?

Alfred E. Neuman, 1955

Java Man

#5: Post by Java Man »

Well done, Ken! Thanks for your continued contribution to the art and science of home espresso!

Cheers,

Rick
Java Man
A.K.A. Espressopithecus

Rainman

#6: Post by Rainman »

I actually have a research background in my distant past, having published articles in (the now supplanted) American Journal of Physiology, as a college student, and in the Journal of Clinical Oncology and International Journal of Radiation Oncology, Biology, and Physics when I was in post graduate training and in practice as a physician. Jim Schulman, who came up with the experimental design and who did the data analysis, has recently obtained a ph.D in Sociology at the University of Chicago. So both of us have experience in experimental design and statistics.
I had a feeling... I'm familiar with a CT surgeon (same name as yours) who we trained (I'm the clinical pharmacist for surgery/critical care at the Tucson VA) a few short years ago, but- ahem, he may be a bit younger than you? I can't imagine he's retired yet, but maybe I'm the one who's getting old... I digress.
I have cobbled together an idealized roast curve ...
I am calling it idealized because although I roast with the aid of a rigid thermocouple mounted in the drum of my roaster, along with a fluke datalogger, I haven't datalogged any roasts in 6 or more months. The only change I've made in my roast technique since the previous datalogged roasts is that I let the drum cool down slightly more before introducing the beans, although it was always under a real temperature of 380F.

EDIT: I made a data transcription error in constructing the first graph I put in this post, which I have just corrected. If you saw this post in the last hour, I apologize for any confusion I may have caused you
Nope- just got in from a quickie bike ride. Thank you for putting this up; I was just curious about your roasting setup, and didn't see too many details mentioned in the article (other than the photo). Which sample roaster is that?
Finally, it is really hard if not impossible to extrapolate roast profiles from one roaster to another, and what works well on my drum might work very poorly in another roaster; you just have to experiment to find what works best in any particular roasting setup.

ken
You mean my iRoast won't produce the same cup using your profiles? :wink:

Thanks again, Ken.

Ray
LMWDP #18

Ken Fox

#7: Post by Ken Fox »

Rainman wrote:[ Thank you for putting this up; I was just curious about your roasting setup, and didn't see too many details mentioned in the article (other than the photo). Which sample roaster is that?


Ray
It is a copy of an old Probat/Jebez/Burns sample roaster whose patents must have run out decades ago. They were being sold by roasters exchange (http://www.roastersexchange.com) --- no I did not make up that URL --- a few years ago but I think they are either no longer being sold by them, or they may be a special order item. I had to wait about 4 months to get mine when it was ordered. The drum was cast in S. America but a lot of the rest of it was apparently made in the shop of Roaster's Exchange.

Judging by what I have seen offered for sale in the recent past, I think that most sample roasters being sold these days roast considerably smaller batches than what mine does. Mine is big enough to allow fairly time-efficient roast sessions as long as you do, say, 5 or more batches each session. I can get up to more than 3 roasted pounds (after roast weight) per hour when I get rolling. Not efficient from the standpoint of a shop, but for something in your garage it isn't bad.

My roaster has been substantially modified from its condition when delivered. It was necessary to replace the burner because the one supplied could not produce enough heat at my altitude (almost 6000 feet) to properly roast coffee. Barry Jarrett was very helpful in locating a new burner for the roaster. In addition I ordered a custom made ensheathed thermocouple from Omega, which has been epoxied in to a constant position and which allows me to monitor the roast temperatures with a high degree of consistency. Finally, as originally supplied it ran on propane but it now is plumbed in and uses natural gas, plus has been mounted permanently under a custom made smoke hood that was fabricated for a friend of mine who has prior experience in HVAC work.

ken
What, me worry?

Alfred E. Neuman, 1955

Matthew Brinski

#8: Post by Matthew Brinski »

Phenominal.

I am actually surprised at your finding that coffee which has been frozen does not deteriorate faster (after defrost) than if it were not frozen initially. I have always had a perceived impression that it does in my use. I don't frequently roast at home though, so the coffee that I experiment with freezing is usually frozen anywhere 2 to 4 days out from roast when it arrives via shipping, as opposed to you freezing within an hour of roast completion. I wonder if that's a considerable variable? Probably not.

Thanks for posting the project. Awesome effort, seriously.

Ken Fox

#9: Post by Ken Fox » replying to Matthew Brinski »

I think it is true, based upon this experiment, that within a certain period of time, previously frozen coffee doesn't deteriorate faster than fresh/never frozen coffee. But none of the coffee in this experiment was tasted at a period older than 8 days. It might be, that had we done a cupping experiment and gone out further, say to 14 days, that we would have found faster degradation.

Aside from a lot of negative stuff that has been said previously about freezing, most of which is unfounded, it is hard for me to come up with a specific mechanism that would cause previously frozen coffee to degrade faster than never frozen coffee. It isn't like you are freezing a head of lettuce, after all. The coffee has already been roasted and whatever cell structure and moisture were there beforehand are mostly lost.

When coffee ages and degasses there are chemical and physical changes going on in the roasted beans. Some of these changes are "good" and some are "bad;" it can't be any other way or we would all strive to drink coffee within a day of its roasting. Most espresso lovers believe that the coffee "improves," over all, during the first several days to a week out of the roaster, and then continues to "hold" for a while after that until the overall quality declines.

My opinion is that freezing greatly slows down these chemical and physical processes, and that the extent to which they are arrested is largely a function of how cold a freezer one uses, and possibly how soon after roasting one does the freezing.

ken
What, me worry?

Alfred E. Neuman, 1955

User avatar
jrtatl

#10: Post by jrtatl »

Thanks for the great article Ken.

As a side note to anyone interested in anecdotal evidence, I almost always freeze my coffee -- with great results.

I buy in bulk to save $$. As soon as the beans arrive in the mail, I use a Foodsaver to vacuum seal 8 - 10 oz of beans in several bags. I then put the vacuum bags in my freezer. I typically use the coffee within 2 months, and it works pretty much as good as the fresh stuff.
Jeremy