Can a grinder cause a burned taste to espresso?

Grinders are one of the keys to exceptional espresso. Discuss them here.
erik996
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Joined: 15 years ago

#1: Post by erik996 »

I run a Mazzer Mini and a La Valentina auto at home. It's plumbed into the water, which isn't hard and comes from mostly snow melt. Flavor of all things is great. Fast forward to now, and I have a Super Jolly and La Valentina semi auto at work. The water is tap water and I run a cartridge softener. My espresso tastes burnt.

The beans are the same, and when I tested the machine at my house (using my 'home' water and Mazzer Mini), it tasted fine. Now that it's at work, it has an underlying burnt flavor. The difference? The grinder and the water. The Super Jolly is new to me, and when I bought it (used from a local roaster/cafe), I completely disassembled it and refinished it. I kept the burrs because upon inspection, they seemed sharp and in great shape. I get a great ~28 second extraction using ~18.5g of ground coffee, great crema, etc....

So, can a wacky grinder cause such a burnt flavor?

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boar_d_laze
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#2: Post by boar_d_laze »

erik996 wrote:So, can a wacky grinder cause such a burnt flavor?
Yes.

"Burnt" covers a lot of ground as a descriptor. It could be the result of rancidity or another taint in the grinder left by bad or flavored beans.

The first variable eliminator/trouble shooting I'd undertake would be to throw out whatever remains of the batch of beans; empty the hopper; inspect the grind path, being careful to remove any chunks which may have found places in which to lodge themselves; (as long as you're in there) check the burrs for proper alignment; reassemble the grinder and run a cleaning media such as converted rice or Grindz; re-season the grinder with a couple of ounces of new beans; finally, dial in the new beans and pull a shot.

If that works, great. If not, you've cleaned your grinder a little ahead of schedule.

Another thing to look (smell) for are the odors which come from misbehaving electrics and/or barbecued insulation. Test by running a clean grinder without any beans for thirty seconds or so, and sniffing.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

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erik996 (original poster)
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#3: Post by erik996 (original poster) »

The taste is akin to charcoal. The beans are from the same source purchased at the same time as my home beans. When I bought the grinder, I took the burrs and carrier off to clean, so there is no residue from before, and I've run perhaps 3 or 4 pounds through it since September. I suppose the next step is to take the grinder home and see if it produces a similar result with my home machine.

This new machine runs a little hotter, but a cooling flush gets it to 190 degree water coming out of the group screen. Maybe this isn't a grinder issue, but I'm a bit stumped right now.

Marcelnl
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#4: Post by Marcelnl »

i Would also test the grinder at home or perhaps better, bring your home grinder to your work machine as the problem is likely in the combination of grinder and that particular espresso machine...
My guess would be the temperature of your office machine is bit off, I run a SJ with my Faemina and ran into some ash tastes lately which was easily cured by lowering the temp (pressure) a tiny bit.
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erik996 (original poster)
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#5: Post by erik996 (original poster) replying to Marcelnl »

Ash taste. That's what I was thinking of, and yes my office machine may be running a bit hot. I do a cooling flush and measure the water temp as it comes out of the group, and cool it to what works at home. This cooling flush is a bit more than at home, but the boiler pressures are similar: fluctuates between 1.05-1.25bar. Maybe I need to put a thermosiphon restrictor in?

Marcelnl
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#6: Post by Marcelnl »

Not sure how you can lower the temperarture on your machine as I am not familiar with its internal structure... but if it helps; I bought an IR thermometer (also for my pizza oven modifications) and noticed that the temp was running at 95'C which I lowered to ~93'C.
Would disregard the pressure and lower the temperature to see if the taste in the cup improves.
In the end there will be some differences between the two grinders so I would skip trying to match parameters and go by taste, correlate taste with measured temp would be a good way or just go by taste ...
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boar_d_laze
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#7: Post by boar_d_laze »

It's frustrating I know. But it doesn't matter if you just cleaned it perfectly and completely before grinding; or if the rest of the bag was great. One bad bean can foul a grinder. And a bad bean might not show itself in the bag, its taint might not manifest enough to be noticed until it's ground.

If the problem is in the grinder, the odds that it's bad bean related are overwhelming, because... What else would it be?

Any grinder related alternatives are far less likely, and related to problems like improper reassembly after your cleaning or burning insulation. You already eliminated the obvious mechanical problems, because when you took the grinder apart you would have noticed them

As I said before, if you take the grinder down, inspect it AGAIN, clean it AGAIN, and carefully reassemble it AGAIN; the worst that happened is you're out an hour and have a very clean, thoroughly inspected, and properly assembled grinder -- not a bad thing.

If it's not bad bean or assembly related, the next step should be thoroughly cleaning your espresso machine (including removing and scouring the block), then pulling a few intentionally under extracted shots by temping too cool. If the burnt taste disappears when the coffee goes sour, you've eliminated the grinder as the source.

I still believe that the most likely explanation is fouling; and don't think you're at the stage where you need to start schlepping equipment from one location to the other ... yet.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator