Where did all the crema go?

[Buschy]

All is not well in coffee land.  :-[. About a month ago I started noticing that the crema was dissipating faster than before.   By the time I pull a shot, steam the milk, then combine the two there is little canvas left to even attempt a squiggle. At first I thought it was the beans. Home roasted Harrar, then Brazilian, then Brazilan/Harrar, then Mexican/Harrar.... Coffee still tastes OK (actually Mexican/Harrar very nice   ) but now the PNG dissipating very fast as well. Whats gone wrong? I dont think I have changed my routine all that much. Beans always fresh. OK... maybe the PNG could degas a day or two more, but overall there is a very noticeable difference. Within less than a minute the crema has gone from 40% or more of the shot to 5% or less. From memory there use to be less crema initially but it wouldnt disappear as quickly.

[Dimal]

Re: Where did all the crema go?

Gday Buschy....

If youre positive that nothing has changed with respect to your Dose and Tamp, and the beans are fresh then I guess it could be related to your machine in some way. How often do you do a chemical backflush on your VBM mate? Could be that there may be some rancid coffee oils or other matter in the Group above the Shower-screen and Water Distribution Block.

Are the shots still pouring within the guidelines of the so-called "Golden Rule"? Have you changed the type of water you use or if filtered, could the filter require changing? Just shot-gunning really as this sort of issue is usually related to the quality of the beans and/or the way you dose and tamp. Someone else may have some other ideas worth trying. All the best Buschy....

Mal.

[stuartgrant]

Re: Where did all the crema go?

Gday,

We had this problem at work, and I suspected a whole lot of things, but it turned out to be that the machine was running hot. Dont know how hot, but our coffee rep turned the boiler pressure down as an interim measure (hes ordered parts from Italy which will sort it out... apparently) and the problem was essentially resolved.

What we did to alleviate the problem before the coffee tech could visit us was to backflush lots before every shot (very time consuming!). What I mean by that is to run ~100-200mL water through the group before pulling the shot. This cools it down... but isnt a perfect solution (temp stability essentially goes out the window here). Try it, and if your crema hangs around, Id say your VBM needs tweaking.

If thats not the problem... I guess your grinder could be playing up (are the burrs blunt? Did you accidentally grind a rock lately and kill the burrs? Is something caught in it?). Mals suggestion of a good chemical backflush is a good option.

FWIW, we almost always have problems with Harars (and some other beans) producing such an oily crema that the oils come out and eat away at the rest of the crema... and then eat away at the milk froth if you drink it with milk. Resting the beans helps, but not much. Ristretto pours are worse than espressi... Not sure if there is a solution there (doesnt actually bother me that much - just makes the coffees less presentable).

Cheers
Stuart.

[Buschy]

Re: Where did all the crema go?

Mmm..well machine is very clean inside and out. I pulled the shower screen/gasket off just over a week ago and there was very little little rancid coffee oil. Chemical backflush is done once a week.

I hadnt thought about the water quality. Our fridge water filter was overdue for replacement but I did that last night and the crema still not much better today.

Timing of shots still very good (25-30 sec, etc.).

Grinder is still next to new and working well.

All of this leads me to believe that it was the Harrars fault, and perhaps the PNG just needs to rest a bit longer. This morning it is only 3.5 days old. If its not the beans, then it sounds like I have a group temperature problem. Can a machine such as mine require temp. readjustment from time to time?

Ill try flushing 150ml before pulling a shot tomorrow and see if that makes a difference. Thanks.

[flynnaus]

Re: Where did all the crema go?

I suspect it is the bean Buschy. I get a fair bit of crema variation on the beans I use and less crema from the bag of Ethiopian Harrar I finished last week.

Might be worth getting hold of a blend and trying it.

If you do decide to check brew head temp, be careful as I was advised by ECA that a small adjustment can make a big difference.
Know someone with a Scace device?

[Buschy]

Re: Where did all the crema go?

I wonder if relative humidity has any influence? 56% today but I believe its been reaching over 70% some days. :P

[damian1]

Re: Where did all the crema go?

I had this with some over-roasted beans. Not too dark, but drawn out too long. It was a very windy day and it slowed down all my roasts significantly.

[Dimal]

Re: Where did all the crema go?

I wonder if relative humidity has any influence? 56% today but I believe its been reaching over 70% some days.  :P

Yes, R.H. and storage temperature before grinding can all affect the way any particular shot will pour. Im with Flynn_aus though, I dont think that there is likely to be anything wrong with your machine given how new it is and that your maintenance regime seems quite acceptable.

If you know of a another CSr close by to where you live, perhaps you could drop around with some of your beans and see how they perform on another machine. Thatd be one quick and dirty way to check things out...

Mal.

[lucinda]

Re: Where did all the crema go?

I was having a similar issue with my classic. I give it a good clean regularly etc etc, but it was well overdue for a srvice, so off she went to the service guy and since its been home its been perfect again.

[Rocky]

Re: Where did all the crema go?

Buschy, I had a thread along these lines recently also. I have just tried several different types of beans from Andys starter packs and whilst I am extremely happy with the flavour I am getting in the cup, the crema is tending towards the minimum end of the scale on the pour and does thin sitting in the cup or when poured over hot water. If the taste of the coffee wasnt so damn good I might suspect the machine was running a bit hot.
Trying to think this through: The crema is composed of oils which the hot water extracts from the grounds. Oil is lighter than water and therefore sits on the surface of the shot. You would think that the shot should be hottest at the point of extraction and lose heat in the cup, however maybe the crema forms a seal on the top of the shot and concentrates the heat beneath it, thereby causing the thickness of the crema to reduce with time in the cup. If the water temperature in the Group was too hot, I would have thought that you would not get nice creamy crema - rather a thin, blond sort of effect.
Another thought: how fast the water goes through the grounds should make a difference to quality of crema, so if you are getting a decent looking pour in the right timeframe then you should be able to rule grind/tamp out as a variable. I get the right amount in the right time and it looks good (rule out grind/tamp) and the taste is neither too sour or too bitter (rule out Group temp) so I tend to think maybe just the characteristics of the beans OR issues of freshness/storage.

[GregWormald]

Re: Where did all the crema go?

Is there a possibility of any detergent left on the surface of the cup? This would easily destroy the amalgam of coffee and oil.

Greg

[Rocky]

Re: Where did all the crema go?

No possibility of detergent with me.
Did a little test this morning: placed a coaster on the top of the cup immediately after pouring the shot to stop it losing heat whilst I finished my shut-down regime with the machine. When I took the coaster off after about 3 minutes, almost all the previously good crema had dissipated. So there is good evidence that the heat of the coffee gradually re-absorbes the crema.

[blanyon]

Re: Where did all the crema go?

Crema will dissipate with time as it is made up primarily of carbon dioxide, this will burn off and bye bye crema, like soft drink the co2 will not last forever.