Coffee expansion and its revelency to the dose of brewing espresso.

[sco Member Find all posts View Profile Close sco]

After a thoroughly enlightening session of advanced training we were sent through at work, one topic that caught my curiosity was the concept of the release of volatile gasses in coffee after roasting.

Primarily the practical wisdom we were given was, more gas; dose lower. Less gas, dose higher.  

Internet searching has yielded little on the topic, so I was wondering perhaps if anyone on this forum knew of an article, guide, in-depth forum discussion where I can learn more particularly about how and why this is so important.

Cheers,

Sam

[Randy_G. Senior Member Find all posts View Profile Close Randy_G.]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

I think that this is just part of the equation- you could just say that anything that causes the coffee to expand more during extraction dictates a lower dose.

The coffee needs room to expand during the extraction. The result of ignoring this can lead to a lot of coffee on the screen, damage to the pucks integrity during expansion causing channeling, low water flow due to over-compacting of the coffee, etc.

A smaller dose can also necessitate a finer grind which can be a factor in better extraction, although that is a relative thing compared to using too much coffee necessitating a too-coarse grind.

[ant_nakedcoffee Member Find all posts View Profile Close ant_nakedcoffee]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

Whilst taking note of the age of the coffees- compare two dosing methods side by side

a) higher dose and slightly coarser grind
b) lower dose and a correspondingly finer grind

Taste them and identify what is unique about espresso from a and b.


From my own experience, with fresher coffee and technique (a) I will tend to have more body (sometimes syrupy), or chocolates, or nutty flavours dominating but the aftertaste might be gone in a flash.  The crema tends to dissipate relatively fast as well.

..and technique (b) I will tend to have an espresso that has less body to it overall, but there may be more caramel to it and fruity or floral aroma that may be missing in (a).  Nowadays I tend to find that with certain grouphead configurations (e.g. e61, synesso) going lower on the dosage will still allow a buttery texture to the espresso and still allow some very interesting flavours to come through.

What I aim to do is to play around with it until I get something that tastes like a wbc definition of espresso- in particular I aim for a nice aftertaste, then concentrate on trying to get fruity or floral aromas, and try to avoid bitterness or sourness while maintaining a decent amount of body.  Another thing you can play with a bit is altering the temperature at the grouphead based upon the age of the coffee if you are allowed.  At veneziano we were easily able to taste a difference of even half a degree in temperature, and it was about balancing the aftertaste.  I used to scoff at half-degree temperature changes back in the day until I was taught how it worked and now Im a firm believer in it.

Having said all this, this is just one interpretation and you will find many more out there.  Try everything you come across because you will learn a lot from everyone you talk to and everyone around you.  Just keep playing around and tasting all your espresso, everyone elses espresso including the crap ones so you can build your taste database.

Hope that helps dude.

[WSullivan Senior Member Find all posts View Profile Close WSullivan]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

Whilst taking note of the age of the coffees- compare two dosing methods side by side

a) higher dose and slightly coarser grind
b) lower dose and a correspondingly finer grind

Taste them and identify what is unique about espresso from a and b.


From my own experience, with fresher coffee and technique (a) I will tend to have more body (sometimes syrupy), or chocolates, or nutty flavours dominating but the aftertaste might be gone in a flash.  The crema tends to dissipate relatively fast as well.

..and technique (b) I will tend to have an espresso that has less body to it overall, but there may be more caramel to it and fruity or floral aroma that may be missing in (a).  Nowadays I tend to find that with certain grouphead configurations (e.g. e61, synesso) going lower on the dosage will still allow a buttery texture to the espresso and still allow some very interesting flavours to come through.

What I aim to do is to play around with it until I get something that tastes like a wbc definition of espresso- in particular I aim for a nice aftertaste, then concentrate on trying to get fruity or floral aromas, and try to avoid bitterness or sourness while maintaining a decent amount of body.  Another thing you can play with a bit is altering the temperature at the grouphead based upon the age of the coffee if you are allowed.  At veneziano we were easily able to taste a difference of even half a degree in temperature, and it was about balancing the aftertaste.  I used to scoff at half-degree temperature changes back in the day until I was taught how it worked and now Im a firm believer in it.

Having said all this, this is just one interpretation and you will find many more out there.  Try everything you come across because you will learn a lot from everyone you talk to and everyone around you.  Just keep playing around and tasting all your espresso, everyone elses espresso including the crap ones so you can build your taste database.

Hope that helps dude.

Great post mate, its something ive noticed too, and its a fine line between the two, i might experiment a little with dosing and grinds tonight and see if i cant get similar results as your self, might have to give the finger sweep a miss if its favorable!,
I did see a set of coffee levelers once on the net that ranged from dead flat being number 1 to quite convex being a 10 or something, idea being to under dose to a measurable level, obviously dosing will need to be consistent to prove anything, anyone tried em?

[acoggins Senior Member Find all posts View Profile Close acoggins]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

I did see a set of coffee levelers once on the net that ranged from dead flat being number 1 to quite convex being a 1

Youre probably thinking of Scottie Callaghans dosing tools. I wont link to a non site sponsor, but Padre coffee/Brunswick East Project uses and sells them. Its possible a site sponsor does too, but Im not aware of any. Ive also seen a few places around town using them.

[Gavin1 Senior Member Find all posts View Profile Close Gavin1]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

Coffeeparts stocks them.

Bit too expensive IMO.

You could probably buy a sheet of plastic and cut your own...

[Thundergod Sleep is overrated Find all posts View Profile Close Thundergod]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

Di Bartoli has them.

Theres a new smaller set which is cheaper than the full kit.

[Intellidepth Senior Member Find all posts View Profile Close Intellidepth]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

And Scottie isnt adverse to you cutting your own  , but the tools are excellent, and durable, better than ice-cream tubs by a long way. I use the home set daily unless Im looking for a certain compression in the coffee that requires my specially curved finger and sensory nerves...

Back on topic: it would take some experience with one style of coffee roasted to the same profile assessed daily over 2-3 weeks for several batches to make a good assessment on the original question. I change too frequently (3 SOs each week) to trial it for you, but you could test-case it yourself and post your findings here.

My observations from multiple coffees is: fresh coffee (say 3 days post-roast for this example)=more gas=larger expanding puck + highly gaseous crema which dissipates = lower flavour dose anyway in the cup, without lowering the actual grammage.

So whilst the theory is correct so your puck integrity isnt compromised, IMO the flavour in the cup is automatically compromised.

[Identity Senior Member Find all posts View Profile Close Identity]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

I also got the home set from Di Bartoli (possibly the same day as TG actually, and use it religiously - in fact, Ill probably move that set to the office and get a full set for home.

ant - id be interested to hear more about your thoughts on body/florals as Im always seeking the elusive floral notes in coffee (while not losing too much body), and coming to the conclusion that a synesso/gs3 group would be the way to go, but as a home user w/ a clued-up wife, I cant see it happening. My experience of the HX E-61s is that theyll get more middle notes happening, but at the expense of citrus/floral notes.

Also finding that lowering brew temp brings out florals more.

& if the expansion is convex.....ie. using an extreme dosing tool (5/6 on the home), are you better with a flat or convex tamper & flat or convex shower screen!

[sco Member Find all posts View Profile Close sco]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

Thank you everyone for your responses. Today was a particularly good day for coffee at the cafe. I estimate that 90% of my coffee pulled within 24-28 seconds, dosed and tamped consistently with this knowledge I can only get better.

[ant_nakedcoffee Member Find all posts View Profile Close ant_nakedcoffee]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

First and foremost, whether you get fruit or floral aromas happening tends more towards finding blends or single origins that are geared towards those flavours in the first place.  What happens next is dependent upon you, and sometimes the changes in taste can be subtle, other times they can be quite dramatic.  I think I should clarify what I think about e61/synesso groupheads.  

To my mind, the la marzocco fb80 is fantastic at allowing you to get different flavours out of your espresso blends and while at first pour I had heaps of fun during the learning process and a lot of what I wrote in my previous post is based upon my short time there.  Ive also been able to play with dosage to a much lesser extent at other jobs previous, but usually a cafe wants consistency.   This is the magic word for customer experience and repeat patronage because were all afraid of challenging their perceptions and having them go somewhere else.  This boils down to the process of attracting and retaining customers being quite difficult, while the process of losing/offending customers is relatively simple.

My time on e61s has only resulted in noting that you get a buttery shot, syrupy and usually well rounded.  I tend to find that dosages on these grouphead configurations seem lower in comparison to other machines that I have used in the past.  Fruity or floral highlights on e61 have tend to be more blend dependent but really I havent had enough experience just playing on one to really find out the possibilities.

Ive only had very limited experience on the synesso, so I cant really comment much on it with regards to dosing styles and taste changes.  They do however allow for a variety of dosage styles and are very nice to work on.

[Intellidepth Senior Member Find all posts View Profile Close Intellidepth]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

Off topic again: I have a VBM. My next machine will have easy-to-change temps included for the very reasons observed above - highlighting more delicate coffees.

I manipulate my roasting to enhance fruity/florals as my E61 grouphead is very consistent in maintaining its temp - flushing drops it very very minimally - its pretty consistent across the shot time. I reduced my temp from its initial configuration by quite a way and also reduced pressure to obtain coffee I prefer.

Back On topic with another extreme example: if youve ever under-roasted a bean, ground it and shot it, youll notice the dramatic expansion of the puck compared to a normal roast of the same bean. Take that bean really dark, and the puck expansion is lower again.

So to complete the theory: if youre using the same roast-level, bean and age of coffee week in week out say in a normal cafe situation, the theory of slightly down-dosing/up-dosing would give you similar sized shots (at least, until the crema settled). However the density/flavour would modify somewhat, just as it also changes day-to-day anyway. Add into that any humidity change and grind adjustments...

[Identity Senior Member Find all posts View Profile Close Identity]

Re: Coffee expansion and its revelency to the dose of brewing espresso.

First and foremost, whether you get fruit or floral aromas happening tends more towards finding blends or single origins that are geared towards those flavours in the first place.

I agree with this, which is why I lean away from most cafe-style blends. Having said that, most of the best-known roasters in the Sydney area seem to have at least one blend with a distinctive flavour profile