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Crema by James Hoffmann
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kingseven
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Posted Thu Nov 23, 2006, 2:23am
Subject: Re: Crema by James Hoffmann
 

caffemela Said:

,

more coffee in the basket = slower pull with dark crema = not enough water to fully extract the coffee = under extraction.
less coffee in the basket = faster pull with lighter crema = too much water and pressure for the dose = over extraction.

Darren Reynolds

Posted November 23, 2006 link

I would argue that even in an updosed basket there is plenty of water to extract the coffee.  I don't think the bulk of the water passing through the puck has reached saturation.  I think the darker crema indicates that more solubles have made their way in the cup in terms of solubles to water ratio - back to Andy S's extraction ratios I guess.

How do you mean more pressure for an underdosed shot?

 
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caffemela
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Posted Thu Nov 23, 2006, 2:39am
Subject: Re: Crema by James Hoffmann
 

You are correct that there is plenty of water to extract properly with more coffee - if the the grind is right.  I usually use a triple basket dosing around 20 to 21 grams of coffee to get the shot I like.  The reason I think that light color = over extraction is that with a double basket and 14 to 15 grams  I get much more lighter coloration towards th end of the shot than with the triple basket.  the same amount of water over less coffee makes more light colored extract towards the end.  The same is true with old coffee which has less good stuff left to extract, the lighter color appears much sooner.

you're also right about the solubles in the cup but that is simply because there is more coffee to emuslify.  this is why I prefer the triple basket.  The overall extraction of each individual particle is less however because there is more coffee to water which results in fewer over-extracted bitter-tasting  grounds.

Also, regardless of the amount of coffee or the rate of pour, if I just let the shots pour into the drain tray for a minute or two, far beyond peak extraction, the color starts as a dark reddish brown and transitions to a blonde and ultimatley almost white or clear.  The coffee is getting more and more extracted ast the color lightens.

I know that pump pressure plays a role but I'm not sure I understand that too well.

I really want to understand this as much as I can so please bear with me.

Thanks,

Darren
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Philosopher
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Posted Wed Feb 14, 2007, 12:57am
Subject: Re: Crema by James Hoffmann
 

I am late to enter this discussion but I found the article and subsequent posts interesting.  As a general text on food science there are not many better ones than McGee's.   I would like to comment on various ideas raised in this forum.  


Crema quantity versus quality

 Based on James' essay, the presence of crema just indicates the elaboration of carbon dioxide and the production of melanoidin - its mere presence gives no indication of the adequacy of extraction.  The colour is the indirect measure of the degree of oil/flavour extraction.

Crema and flavour

 Based on the above perhaps the added taste experience of crema is addition to the actual presence of flavour compoents of the coffee.  Perhaps it is the physical properties of foam that either affect taste perception or the chemical propertites of of carbon dioxide (and hence carbonic acid) which accentuate the flavour.

 This observation correlates with the effect from drinking champagne with its fine mousse or from a well poured Guiness.  Flat versions of either will taste different and provided a different and less exciting sensation.  For some reason cheap version of champage where CO2 is introduced does not provide the same effect - the bubbles have to be small.  In champagne these are formed at fementation, in espresso - from gas trapped at roasting.

Crema and oxygen exposure

 It seems a inviolate principle that espresso should be drunk immediately after extraction.  But taking the wine analogy again, perhaps some degree of oyxgenation and also allowing the expresso to 'breathe' will enhance the flavour.  Maybe there is an optimal period of oxygen exposure.   Nevertheless taking both to the extreme will result in a rancid product.

Tiger striping/Mottling

 My interpretation of the striping is the sum of water channels from early extracted, middle extracted and late extracted grounds.  The reason for this irregularity I alluded to in another post:

"Tamping Science, Theory and Practice, Part One by Mark Prince"?Page=9

The combination of orange, brown, pale flows would suggest different chemical compositions.  I know people have speculated about what each of these contain but do we know for certain what these represent and in what proportion should these combine?  

 I would also assume that the finer the striping the more evenly extracted the grounds are.  Broad striping would suggest significant water channelling.  In an ideal situation there actually would be no colour variation at any point in time but the entire pour will alter colour in synchrony.

Crema, oils and extraction

 James comments that crema itself is not synomynous with adequate extraction of oils, just even extraction.  Could I extrapolate this to mean that the extraction of important volatile oils does not require the production of crema at all.

All in all it seems that the actual production of crema is a totally separate issue from the extraction of flavours/oils.  Maybe future attempts at manipulating the resultant shot should focus on these things separately.
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alanfrew
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Posted Wed Feb 14, 2007, 3:15am
Subject: Re: Crema by James Hoffmann
 

Sorry, o Philosopher, but thou art full of it (to use a quaint post-philosophical Aussie  expression.) You have picked up the superficial factors without understanding the deeper ones. Crema alone is a whole lot more than just CO2 and melanoidin. I would recommend reading the books James mentions in his bibliography as a minimum starting position, followed by the purchase of a decent espresso machine and grinder combination and a LOT of really, really fresh coffee.

Based on James' essay, the presence of crema just indicates the elaboration of carbon dioxide and the production of melanoidin - its mere presence gives no indication of the adequacy of extraction.

This statement is a bit like saying that the mere presence of the sun gives no indication of its importance to the continuity of life on earth. In both cases, you need to contemplate not the presence, but the meaning and effects of the absence. Then, Grasshopper, you can go forth into the wide world, portafilter firmly in your grasp, and start doing something other than thought experiments.


Alan
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Philosopher
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Posted Wed Feb 14, 2007, 4:43am
Subject: Re: Crema by James Hoffmann
 

alanfrew Said:

Sorry, o Philosopher, but thou art full of it (to use a quaint post-philosophical Aussie  expression.) You have picked up the superficial factors without understanding the deeper ones. Crema alone is a whole lot more than just CO2 and melanoidin.

Then, Grasshopper, you can go forth into the wide world, portafilter firmly in your grasp, and start doing something other than thought experiments.


Alan

Posted February 14, 2007 link

Master, I am just quoting the remarks James makes in his essay.  He says the physical substrate for the crema are bubbles of CO2 which are coated with the proteins, melanoidin and oils formed from the extraction.  It is clear that the crema you see is a composite of these ingredients.  However, what the essay seems to suggest is that CO2 production and flavour extraction are partially independent variables and may need to be treated as such.  The fact that bean choice can produce crema without adequate flavour would support this.


I acknowledge your empirical experience and don't wish to challenge this.   I take your jibe at thought experiments as a compliment.  You and many others on this site are trying to link the empirical with the theoretical.  Better insights into the theory may allow you to optimise previous approaches.

Your retort seems to be asking me to direct my efforts with the old imperfect tools which have been used for decades even though they actually don't perfectly achieve the things that you theoretically claim they can.  Maybe you need to think out of the square.
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kingseven
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Posted Wed Feb 14, 2007, 2:19pm
Subject: Re: Crema by James Hoffmann
 

I will stick my oar in and maintain that crema and quality are not directly related.  It just says, imho, that certain boxes in the brewing process were ticked.

I could quite easily make a very horrible espresso, with a thick and luscious crema - the bad taste coming from a bad roast, poor quality greens and a dirty machine.

 
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alanfrew
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Posted Wed Feb 14, 2007, 6:31pm
Subject: Re: Crema by James Hoffmann
 

kingseven Said:

I will stick my oar in and maintain that crema and quality are not directly related.  It just says, imho, that certain boxes in the brewing process were ticked.

I could quite easily make a very horrible espresso, with a thick and luscious crema - the bad taste coming from a bad roast, poor quality greens and a dirty machine.

Posted February 14, 2007 link

Correct. Crema can tell you a lot about the quality of your extraction. What it can't show is the actual taste of what's being extracted. However, if you have a known good coffee and you're not getting good crema, you won't be getting good quality espresso, either.

Alan
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Philosopher
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Posted Wed Feb 14, 2007, 7:03pm
Subject: Re: Crema by James Hoffmann
 

I will stick my oar in and maintain that crema and quality are not directly related.  It just says, imho, that certain boxes in the brewing process were ticked.x]

Thank you.  This is exactly the point I was trying to get across.  Though it is probably true that a crema-less coffee has not been ideally extracted or will taste good (quoting Alan), the reverse is not true (quoting James)

I would maintain that crema is a helpful marker/indicator that the extraction went well but is not the sole constituent/factor that governs the taste of the coffee.

It is because people don't realise this you get the perverse situation where they aim to get the crema but yet not obtain the flavour.  Hence the proliferation of pressurized portafilters, overuse of robusta beans etc.

Even in my limited experience I have found that some of my more crema-filled pours taste even worse than ones with less crema.

If we focus on getting a good extraction, maybe the aesthetic qualties of crema comes with it anyway.  However, attempting to reverse engineer the solution by pursuing crema will not necessarily achieve the result we would hope.

May be we need to examine more closesly about what actually happens during extraction and not specifically on what happens when crema is formed.    

You can read my philosophical ramblings about this on the Tamping science thread:

"Re: Tamping Science, Theory and Practice, Part One by Mark Prince"
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Philosopher
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Posted Wed Feb 14, 2007, 7:21pm
Subject: Re: Crema by James Hoffmann
 

alanfrew Said:



Then, Grasshopper, you can go forth into the wide world, portafilter firmly in your grasp, and start doing something other than thought experiments.


Alan

Posted February 14, 2007 link

Master, you may ask why I pursue such ethereal concepts.  I guess if we could eliminate as many of the variables that lead to inconsistent results then good espresso become more accessible to the multitudes.

It is testimony to an accomplished Barista that with such imperfect tools, they can achieve such wonderful results.  As revolutionary as espresso machines have been the past century they are subject to a huge number of machine/man variables such as:

Constancy in temperature - finicky thermostats, inadequate thermal mass, thermal lag
Constancy in pressure -
Variations in achieving even compaction

This is not even considering factors affecting the bean itself.

Perhaps we need a new paradigm?
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Neozin
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Neozin
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Posted Mon Feb 19, 2007, 7:51pm
Subject: Re: Crema by James Hoffmann
 

I am really impressed! Thanks for such important lecture for me!
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