This page is - The Full Story : Pressure profiling

The story:

A simplistic view is this - the old-fashioned formula in espresso training was of  7gm, 9 bar, 30ml, about 90C, 25 seconds.  We now seem to have got to the stage where none of these items needs to remain constant!

What are the practical possibilities of this for the decent-quality coffee bar?  To what degree is it reasonable for the working café to say: ‘yes, I have now determined that the absolute best profile for my house blend is this grammage, this pressure, at this temperature… but for my guest coffee, it’s going to be x seconds at four bar, slow rise to nine bar, then whack it down to 6 bar for the last five seconds’.

Is this all going too far?  Are we expecting café owners to spend long night-time hours tweaking their brews in miniscule amounts?  Or is it both practical and worth while, and are we on the verge of a breakthrough in quality brewing, which will extend to the average high street?

What is pressure profiling?

And should the high street coffee shop be aware of it?

August 2010

*

One of the biggest discussion points in the modern espresso market is the relatively new question of ‘pressure-profiling’. It is not a new process in itself – it is essentially a new name given to an old process.

In the old days of lever espresso machines, baristas worked the water flow more than a straight ‘on and off’. The skill was in ‘feeling’ the pressure of the water as it passed through the coffee. As espresso machines became more automated, the ‘feel’ became less important, and brewing parameters became standardised – typically, 7gm of coffee, 9 bar of pressure, and 30ml water at about 90C, for 25 seconds. With a decent coffee, properly ground, that formula should guarantee anyone an acceptable espresso.

Recently, things began to turn in a circle – it was recognised that in the old lever machine, the pressure did not stay constant during the brew. The manual action would give a lower pressure at the start of the shot, increasing to a higher pressure. Modern espresso manufacturers said ‘let’s replicate this on modern machines – we’ll allow the barista to change the water pressure while the shot is brewing’. And, as always happens, manufacturers followed each other in pursuit of the trend, working to achieve through high technology what the original baristas achieved with a pair of hands!

And much of it was on show at the recent Caffe Culture exhibition.

But how important is this? Are we on the verge of a breakthrough in quality brewing, which will extend to the average high street?  Or is this an unnecessary step too far into the world of the coffee geek?Is it practical for the working coffee house owner spend time experimenting until he can say: ‘I have now determined that the absolute best profile for my house blend is this grammage, at this temperature, and I shall now put the water through at four bar for five seconds, increase to nine bar, then whack it down to 6 bar for the last five seconds’.

The UK’s first world barista champ, James Hoffmann, recently helped the debate along when he wrote: ‘pressure profiling is undoubtedly going to become more readily available’ through newer espresso machines. However, with delightful honesty, Hoffmann did acknowledge that while investigating the question for himself, even he felt lost: ‘juggling dose, grind size, flow rate, volume of espresso and time is enough… changing one variable often resulted in chasing my own tail. I often ended up defaulting back to a very simple profile, which seems to be quite a popular one online: a relatively lower pressure pre-infusion period to soak the cake (5-8 secs), a smooth, relatively quick rise to 9 bars over 2-3 secs., a period of 9 bars for 7-10 seconds, and a declining pressure from 9 bars down to 8 or perhaps lower.’

One big argument is that we are electronically replicating the work of the old lever espresso machine, which extracted the brew at varying pressures depending on the touch of the barista. Such machines were in use in the first Soho coffee bars, where the Drury company blended the UK’s first domestic espresso blend.

“We would have known about this in Soho… but we would not have analysed it!” agrees Drury’s Marco Olmi. “The concept is valid, although some of it is operational nonsense. It’s all very well so long as you don’t get caught up in the technology at the expense of serving the customer.  Remember, you’re supposed to be running a commercial business, not spending all your time fretting about whether you can set the parameters for the world’s most perfect coffee.

“I have often had buyers say to me that customers want a ‘more general taste’ rather than a blend I’ve prepared to perfection. So, I’ve had to accept that perfection can be valid… but really, perhaps you should be spending that time serving coffee!”

At La Spaziale, one of the pioneers of absolute precision in brewhead temperature, director Steve Penk has seen the most perfect espresso in action during his time as chairman of the world barista championships… and he’s not convinced.

“The whole pressure profiling debate leaves me cold, and I personally believe it is a lot of hot air over nothing. I believe it is unproven, supported by a few who struggle to sell machines in serious espresso markets across the world, and most importantly I have seen little in way of proof that it produces a better espresso.”

Interestingly (and entertainly) he is supported by one of his great rivals, Dalla Corte. Paolo Dalla Corte said this:

“We have to bear in mind that in the last 50 years no serious evolution on espresso coffee machines has ever been made for the benefit of the coffee. This was until 2002, when Dalla Corte perfected group head temperature control. The market criticised and played down this technology for 3-4 years until today, where several manufacturers are commonly doing the same with multi-boiler systems and energy-saving devises.

“Now we have the latest discovery - the extraction profile.  This is a very BIG IDEA from a marketing point of view. This idea can find a space in the market place for sure but how a big a space is very questionable.

“After all, the old lever machines of the 1950’s could control pre-infusion and affect extraction and taste profiles without being scientific.

“Firstly let’s come back to more basic technical matters. From my experience, every modification that you make to one of the extraction variables below creates a far wider difference to the result of the coffee in the cup than pressure profiling will ever achieve as an impact on flavour.

Starting from the reference values as:

- Ground coffee dose 6.5-8,0gr

- Quantity of coffee extraction 25ml -35ml

- Extraction time 18-30 seconds

- Water pressure on the ground coffee at about 9 bar 

“On top of these four variables, the water temperature used for the extraction of the coffee is the one critical additional variable that will considerably affect the result in terms of taste, body and aroma of the final coffee obtained.

“Every time we do a presentation or during an exhibition, we give our 3 group Dalla Corte Evolution machine three different temperatures on each group head, of only 1 degree centigrade. The other variables are constant yet the taste difference astounds people.

“So now someone is saying that they modify the taste profile during the extraction using variable water pressure!

“Certainly, something changes but not in the way that it is “sold” to us  i.e. the explanation given by the sales and marketing people.

“It is clear that by modifying the water pressure during the coffee extractions something changes, but how much? And at what price? And is the result worth it?

“I think that these are all questions a manufacturer should ask themselves before putting something this confusing and new into the market. It could be far more important to work on others factors that effect flavour first. It is quite useless to talk about taste profiles that can be modified in the cup and then use an espresso machine with a softener, where the coffee quality can differ from cup to cup and where water is also submitted to oxidation and can therefore lose aroma before being used. Another example of this is using water with a high concentration of calcium and with a PH that is too high or too low. The variables of final taste are uncontrollable.

“These kinds of things are just some of the factors that may significantly influence the final cup and they are far more important to control than varying the pressure during the coffee extraction.

“So I conclude that the market is asking us for more and more systems that are easier to operate in busy locations on a daily basis and that give the operator the possibility of obtaining better espresso at 90/95% of its potential quality.  If you then try to get another 2% more out of it by introducing pressure profiling, you underestimate the bigger factors that influence 30/40% of the taste and the risk then is that you end up producing machines that are very complex and expensive. This is a job that Dalla Corte will leave to others.”

At Watermark, which has recently taken on the UK responsibility for Gaggia machines, David Lawlor is unconvinced.

“We would not dismiss it, but neither would we say it’s the big breakthrough. Yes, it will make a difference to flavour, but whether it counts as an improvement is a matter of taste. 

“The issue is of whether your espresso machine is required to give you consistency, or to give you the opportunity of inconsistency. The difference is between the matter of what you can do, and the practicality of what you need to do. Are these things nice to be able to do? Yes. Are they always practical in a coffee shop? Often not!”

However, several significant brands unhesitatingly say they are un favour of pressire-profiling in various automated forms.

With great fanfare, La Marzocco introduced its Strada at the recent Caffe Culture show. This really has been much-awaited, since a prototype was seen in America in 2009. The fascinating aspect of this is that there are two machines – one has a mechanical pressure control, worked by hand with a ‘paddle’, and the other is fully electronic, allowing for profile ‘recipes’ to be saved and repeated automatically.

“The mechanical paddle adjusts the flow released on to the puck,” the company told us. “Each group is controlled by a paddle which works on a mechanical valve. We can pressure-profile from zero bars to nine bars, and the barista can easily see the results of their experimentation – they are effectively replicating the effect of the old lever machine. The electronic version takes it to a whole new level. On that, you are working from zero to 15 bars, and in this case the paddle controls a rheostat, which gives greater variation, and also quicker.

“The interesting thing for baristas is simply this - it helps you achieve different results from the one coffee.”

Another enthusiast is La Cimbali, where Matthew Tuffee argues that if you take the time to find the right parameters, his latest machine (the M39HD) allows the operator to save and repeat that recipe.

“The really advanced feature is to be able to adjust and the pressure profile by the touch of a button. So, you can set to perhaps 4 bars for four seconds, and your control mechanism is just a matter of touching up or down from there… and then save the profile.

“We had trade customers bring their own coffee to Caffe Culture to play with it on the machine. We set it to a traditional nine bars, then we invited them to use their own coffee, change the pressure settings, and taste the difference.”

We can expect to see more new blends which will need more than the average 9 bar pressure to achieve the best taste experience, says La Cimbali. 

 “New blends seem more sensitive. If roasters are going to all the trouble of sourcing and blending more creatively, and if you’re spending good money on their work, then although we know that nine bar does a brilliant general job, it is now worth going a step further to see whether another move will bring you the utmost flavour.

“As the WBC has proven over the years, the new generation of barista and potential coffee shop proprietor is questioning the norm and pushing coffee production boundaries to new heights. More single-origin coffees and ever changing house blends will require more flexibility and involvement from the barista to ensure perfection in extraction is achieved each and every time.  We see our machine being a major contributor to this, as it can be easily programmed and it then remains constant, even if the barista changes!”

At Caffe Society, importer of the Brasilia brand, Steve Mooring is convinced of the value of pressure-profiling in technical brewing, but he does warn that it is not for everyone.

“If you want to make the best coffee, this is the way to go.  Yes, you can now play with more permutations - every coffee has its optimum brewing recipe, and now you can find it.

“At the moment, if you set your grind properly, you should always be able to get a good espresso – do the same on the Brasilia Sublima, and your espresso will go to a different level.

“But to get the very best, you must spend a serious amount of time tweaking and tasting. So this is not a mainstream subject. We’re probably talking about ten per cent of the coffee-house market… but that market does exist, and there is a large enough ‘geek’ market to make it worthwhile for us.”

 *