Caffeine Extraction in Espresso

[oneday]

Long ago I read somewhere that caffeine isnt the most soluble substance, at that therefore most caffeine was extracted during the latter part of the espresso shot (around the 20secs mark i think). hence ristretto being sweeter than espresso.

to me this was quiet puzzling, as i always considered caffeine to be very soluble, especially at around 93C. This was backed up by what I read in Illy and Viani, where they state that caffeine density is greatest during the earlier parts of the extraction (around pp300 for those that have the book i think)

So Im left a little confused. Is the mantra of caffeine extracted during the latter stages of espresso extraction wrong? or perhaps that it takes a certain volume of caffeine to become susceptible to the human tongue, and that volume being attained only after (lets say) 20secs.

cheers,
j

[luca]

Re: Caffeine Extraction in Espresso

This was backed up by what I read in Illy and Viani, where they state that caffeine density is greatest during the earlier parts of the extraction (around pp300 for those that have the book i think)

That strikes me as more or less a correct interpretation, but the numbers are fairly small. If you look at p299, there is a graph of caffeine weight vs ristretto volume that is taken as the beverage is extracting; at least thats my reading of it. Im looking at the 2nd edition. This graph looks to me to show that caffeine extraction does drop off towards the end of the brew, but I think that the difference is small enough that we might as well think of it as though caffeine extracts linearly with volume when we are thinking about a shot that is not overextracted.

So Im left a little confused. Is the mantra of caffeine extracted during the latter stages of espresso extraction wrong?

Yes, I think so.

or perhaps that it takes a certain volume of caffeine to become susceptible to the human tongue, and that volume being attained only after (lets say) 20secs.

Probably, but I suspect that perception of the taste of caffeine will be determined by concentration, not by total volume. You could test this by tasting the first part of an espresso and then tasting the last, but ... and here is the huge BUT ...

Coffee is a beverage that contains many, many, many chemical constituents. Caffeine is one and it makes up a small percentage, and one that tastes pretty bad at that. If you have a chance to taste pure caffeine, do it, but be conscious that it should be tasted at low concentrations - the person preparing it will probably have to dilute the solution twice. The taste is very bitter. Chewing on an aspirin is a good analogy, as is drinking tonic water and focussing on the bitter flavour. One would think that removing caffeine would be a great way to make coffee taste better. I explored this in my last article in BeanScene magazine; in a nutshell, it does not. This is because caffeine isnt even the major contributor to bitterness in coffee; the figures that I have seen are that caffeine only makes up 10 to 30% of the perceived bitterness of coffee.

So what makes up the bitterness in the cup? Theres a hint in the two things referred to before: what we think of as asprin is acetylsalicylic acid and one of the large contributors to bitterness in coffee is thought to be cholorgenic acids, which break down to give stuff like quinic acid (and quinine is the bitter compound traditionally used in tonic water). Another compound that gets mentioned as a cause of bitterness is trigonelline.

Beyond all of that, Im sure that people have heard ad nauseum that coffee contains a heckuva lot of different chemicals; something like 800 and counting. Now before people freak out, they should reflect on the simple fact that everything that we eat contains chemicals and that chemicals are not necessarily poisonous. Honestly, wed probably suffer from a lot less hysteria if people used words like "components" or "constituents" or "things" instead of "chemicals". If you dont like the idea that things you eat contain chemicals, then do yourself a favour and do not google up a list of the chemicals commonly found in an apple! I always scratch my head a little when people single out caffeine. Sometimes people will tell me that they dont drink coffee because "caffeine gives me jitters." I seldom ask them how they have eliminated the other 799 chemicals as a possible cause. A dead giveaway that its not even worth having the conversation is when the person that says that does so over a tea or coca cola! I also tend to scratch my head when people who are interested in specialty coffee put caffeine molecules over everything. Specialty coffee is supposed to taste good. Why focus on something that tastes bad? When was the last time that you saw a wine geek idolising trichloroanisole? Why not draw up a nice vanillin molecule instead?

Personally, I take the view that caffeine isnt something worth worrying about. If you have health concerns, see a doctor. If you dont, why not focus on something that actually tastes good?

Cheers,
Luca

[Thundergod]

Re: Caffeine Extraction in Espresso

Beyond all of that, Im sure that people have heard ad nauseum that coffee contains a heckuva lot of different chemicals; something like 800 and counting.Now before people freak out, they should reflect on the simple fact that everything that we eat contains chemicals and that chemicals are not necessarily poisonous.Honestly, wed probably suffer from a lot less hysteria if people used words like "components" or "constituents" or "things" instead of "chemicals".If you dont like the idea that things you eat contain chemicals, then do yourself a favour and do not google up a list of the chemicals commonly found in an apple!I always scratch my head a little when people single out caffeine.Sometimes people will tell me that they dont drink coffee because "caffeine gives me jitters."I seldom ask them how they have eliminated the other 799 chemicals as a possible cause.A dead giveaway that its not even worth having the conversation is when the person that says that does so over a tea or coca cola!I also tend to scratch my head when people who are interested in specialty coffee put caffeine molecules over everything.Specialty coffee is supposed to taste good.Why focus on something that tastes bad?When was the last time that you saw a wine geek idolising trichloroanisole?Why not draw up a nice vanillin molecule instead?

Personally, I take the view that caffeine isnt something worth worrying about.If you have health concerns, see a doctor.If you dont, why not focus on something that actually tastes good?

[smiley=tekst-toppie.gif]

[GregWormald]

Re: Caffeine Extraction in Espresso

This graph looks to me to show that caffeine extraction does drop off towards the end of the brew, but I think that the difference is small enough that we might as well think of it as though caffeine extracts linearly with volume when we are thinking about a shot that is not overextracted.

Somewhere recently I saw a graph of the extraction rate of the major flavour chemicals, and the pleasant ones were definitely in the first part of an extraction. (Sorry, I cant remember where I saw it. )

So the above interpretation would imply that in proportion to the desirable flavours, the caffeine proportion of the extraction increases as the extraction lengthens--thus increasing the bitterness. Id guess that this may apply to other bitter chemicals as well.

SOMETHING has to explain the sweetness of a ristretto compared to the bitterness of longer extractions.

Greg

[A_M]

Re: Caffeine Extraction in Espresso

This graph looks to me to show that caffeine extraction does drop off towards the end of the brew, but I think that the difference is small enough that we might as well think of it as though caffeine extracts linearly with volume when we are thinking about a shot that is not overextracted.

Somewhere recently I saw a graph of the extraction rate of the major flavour chemicals, and the pleasant ones were definitely in the first part of an extraction. (Sorry, I cant remember where I saw it. )

So the above interpretation would imply that in proportion to the desirable flavours, the caffeine proportion of the extraction increases as the extraction lengthens--thus increasing the bitterness. Id guess that this may apply to other bitter chemicals as well.

SOMETHING has to explain the sweetness of a ristretto compared to the bitterness of longer extractions.

Greg

I posted a link to a Uni in the USA or Canada / Aficra ??? Was a white paper on extraction of coffee and flavours... YES... Good chems get leashec out at the start.... The other less deseriables the longer the run.. The more nasties..

From my i-brick... So can not search as I would like..