Before I jump into this topic, I just want to say that we make espresso with the tools we have, and for the most part a good barista can pull a fabulous shot with their tools…however, there are certain advancements in technology and knowledge for the extraction of espresso that have aided our understanding for how to do it. So with that said I’ll jump into the science we use to affect the art of pulling espresso…
The thermal stability of an espresso machine has been established. The synesso and gb5 have both applied PID heater control to limit temperature variance to within .1 degrees F. We can even retofit a Linnea (or any hx machine if you really wanted to) with the digital technology to heat water with less variance in temp. The thing I’m really surprised by is the the lack of discussion in regards to water pressure. Water temp. and pressure have such a close, mutually dependent relationship (something I should have learned in middle school instead of on the espresso machine) and the pressure the water is under when it hits the espresso has a major effect on the flavor of the shot. There is discussion about this, but it definitely is not nearly as pop (sub)culture as temperature stability.
Most espresso machines control pressure using a rotary pump. Line pressure is boosted to 9 bars (boiler pressure) during brewing. But what happens when you are pulling an espresso and your coworker hits wash on the dishwasher, your customer flushes the toilet and your brewer refills? The incoming line pressure to your machine drops by 10 pounds of pressure or maybe even more! If we are going to get excited about the stability of a tenth of a degree for water temp, then why not a half bar of pressure?
My prediction (and really, this is already being done by operators) is that espresso machine manufacturers will build a machine that has a static water tank built in. A small electric pump will pull water out of the tank and feed it to a rotary pump at +/-40 pounds of pressure that is then boosted to 9 bars. Set this up for each group and you have 100% pressure stability. (I think this would likely make actual brew temperature more stable too)
As I put together my workshop this is my plan…along with a mix if distilled and hard water (also a lot easier than plumbing my garage!) Although, I probably won’t enjoy drinking my espresso in a garage compared to the aesthetic of a downtown cafe sharing a table with friends! So maybe all this science is at a loss w/o a little perspective…
But back to the science!…As a barista I am trying to understand and control the varying factors that affect the extraction of my espresso. I can’t control the temperature, pressure and humidity of my environment, but if I can isolate, control and understand the variables that are manipulable (by hand/machine) then I can have a pretty good chance of pulling a great shot of espresso. I would argue that brewing pressure is the most over-looked variable.
It would be nice to see some cool ways that a manufacturer meets this undervalued variable.
2 responses so far ↓
summer // 25 June, 08 at 7:23 am |
this is way too much science for me…Colin was reading over my shoulder though and seemed a bit geeky about his interest…I’m sure if he had time to do such things as read and contribute to blogs he’d follow yours:)
I just like a yummy shot and you always provide it. woo hoo.
thutlephaphy // 2 August, 08 at 8:08 pm |
Very nice!!