Posted Fri May 8, 2009, 5:32pm Subject: What's wrong with blade grinding?
I've been using a blade grinder for a long time, but now I've done some reading on this site, and I see the unanimous opinion that blade grinders give inferior results. I'm skeptical. I did use a Kitchen Aid burr grinder for a couple of years, and I didn't like it a bit. Before that, I used a hand grinder for a little while. My Krups blade grinder has seemed to me to work as well or better. I've seen the comment that blade grinders produce an uneven grind, but it doesn't look uneven to me. And what's wrong with an uneven grind, anyway?
However, mine is just an impression, and I'm quite willing to believe that some rigorous comparisons have made which demonstrate the inferiority of blade grinding. I'd like to revisit this question, and thought perhaps someone could point me to where some real evidence is given.
Posted Fri May 8, 2009, 6:40pm Subject: Re: What's wrong with blade grinding?
Doing a search will give you a ton of information on this topic.
From what I know blade grinders do grind uneven. This is really important if grinding for espresso, french press, vacpot, etc.; but doesn't matter as much if you're just grinding for drip. I used a blade for a short amount of time with my press and the results were horrible compared to using a quality burr grinder. Key word here is quality, if you're using a cheap $50 burr grinder from Target you might as well just use the whirly-blade.
Another bad thing about a blade grinder is that it generates heat which can damage the beans.
JR Senior Member Joined: 31 Mar 2003 Posts: 1,833 Location: Germantown, TN (right next to Elvistown) Expertise: I love coffee
Espresso: New but inop Quickmill... Grinder: Baratza Forté, Cunill... Drip: Bona Vita (Thermal) Roaster: GG/UFO
Posted Sat May 9, 2009, 6:09am Subject: Re: What's wrong with blade grinding?
I use a "blade grinder" (note the quotes, because it's NOT really a grinder) at work because it was a very thoughtful gift from employees. I use a Cunill Tranquilo at home. I can say from experience that the blade grinder is better than using pre-ground coffee, and I was pleasantly surprised at how well it does. I would not use it for espresso as the grind is way too uneven, nor would I use it for press pot because of the fines. Regardless how long I grindchop, I still have some larger pieces. These do not saturate well and thus do not contribute to the cup at all, they just take up space in the filter. So the coffee is not as strong as what I get at home. I've tried shaking the machine while it's running, and that helps--but not a lot.
As for heat generated by the process, in theory, that's correct. I have not seen any kind of experiment to quantify the heat generated by this, compared with real grinding. So we all have opinions, and mine is that this is negligible, especially in light of the real problem--it's just flailing at the beans.
Posted Sat May 9, 2009, 8:20am Subject: Re: What's wrong with blade grinding?
Yes, I shake the blade grinder/chopper, too, and I continue the action until I no longer hear the cracking sound as the blade hits large bean fragments. Dark roasts, what I use, get finely divided more quickly.
Posted Sat May 9, 2009, 9:02am Subject: Re: What's wrong with blade grinding?
I have heard all the criticisms of blade grinders too. For years i used a Krups blade grinder. A 32 second run full of espresso beans, coupled with shaking, produced a fine enough grind for two double shots. I smelled nothing like burning. My first acquisition of a burr grinder, a gift, was a Cuisinart. That could not even approach an espresso appropriate grind. I got a Capresso Infinity. Posts on this site say it is decent. It can choke an espresso machine on the finest setting, reviewers report. Not mine. As i write this it is in for warranty service because it could not grind any better than the Cuisinart. If it doesn't do the job when it gets back here, i think i will pull out the Krups. J.
Chang94598 Senior Member Joined: 24 Oct 2007 Posts: 213 Location: SF Bay Area
Posted Sat May 9, 2009, 9:34am Subject: Re: What's wrong with blade grinding?
The blade "grinding", ie, impact grinding, does not allow easy control of particle size.
As previously posted, at least for espresso, in the article by S Andueza in J Agric Food Chem 2002, 50, p7427, it was mentioned the particle distribution is as follows: 50% >500 micrometer 21% 400-500 micrometer 25% 300-400 micrometer 2% <200 micrometer
Modern method to particle measurement is via laser diffractometry. You can find more information by reading "Handbook of Powder Science and Technology", New York, 1984, "Crushing and Grinding Process Handbook", John Wiley & Sons, 1987, and of course, the much mentioned Illy book.
You may not be able to feel the grinding temperature, but at point of impact, the temperature reaches 100C, about water boiling temperature. The coffee oils which are inside cell walls that are sticky at below 40C become fluid, migrate outward, coat the coffee particles, then become sticky again as ground coffee cools to room temperature. This has significant consequences during formation of the espresso coffee cake, because the excessive surface oil changes fluid dynamics. This is another reason blade impact grinding is unsuitable for espresso, even if the particle distribution is the same in comparison to burr grinding.
Finally, increased grinding temperature also hastens degradation of various thiol compounds that are responsible for the aroma and freshness of coffee, which you can read more about by searching coffeegeek forums.
Posted Sat May 9, 2009, 11:16am Subject: Re: What's wrong with blade grinding?
I think you are missing the point here
"I've seen the comment that blade grinders produce an uneven grind, but it doesn't look uneven to me."
This guy has made up his mind, he's tried a Kitchen Aid and a nameless hand grinder. No matter the evidence re particle size which is out there, we aren't going to change his mind. He needs to taste the difference and short of going round to his place with a Ditting, I don't see that this can be done with all the references in the world.
Like evolution re "creationism" the evidence is out there but you aint gonna convince everyone.
Doesn't seem reasonable to me. As Press_Pot observed, results comparable to a $35 "burr" grinder (i.e. terrible) is not much of a test. As hundreds (thousands?) of folks have posted on this site, the Baratza grinders and the Capresso Infinity are really the entry level for press pot use. (the objective here is an even, coarse grind with minimal fines)
My first acquisition of a burr grinder, a gift, was a Cuisinart. That could not even approach an espresso appropriate grind. I got a Capresso Infinity. Posts on this site say it is decent. It can choke an espresso machine on the finest setting, reviewers report. Not mine.
I can't imagine why any experienced espresso user would suggest that the Capresso Infinity is a "decent" grinder for espresso. Why would you think the rest of us are paying several times the cost of that machine for our espresso grinders? When it comes to grinders you get what you pay for and acceptable entry level espresso grinders such as the Ascaso I-mini, the Gaggia MDF, the Le'lit PL53 or the Cunill Tranquilo are in the $200-280 range. Most everything else (Rancillios, Mazzers, Macaps, etc) is up from there. (the objective here is fine grind capability with a high level of consistency and precise adjustability)
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