This article is taken from http://www.lamarzoccousa.com and is quite interesting. If you are considering opening a Cafe, familiarize yourself with your target volume and which machine is best for you. Semi Automatic or Volumetric?
“We recently invited Ben Kaminsky to team up with the La Marzocco USA Lab crew in Seattle to investigate volumetrics, and to see whether better consistency is achieved by having an experienced barista prepare espresso on a semi-automatic espresso machine, or if more consistent results are achieved through volumetrics.
The following is Ben’s write-up on the testing and the results.
It’s certainly no secret that in the business of specialty coffee (or really any business for that matter), consistency is king. Yet, for all our talk within the coffee industry of being consistent and using the best possible tools to achieve consistency in quality, how much do we actually do to enable baristas to be consistent?
Whether you choose to subscribe to the SCAA’s guidelines on extraction or not, one thing is for sure–whatever you do like, the goal is to repeat it over and over again in order to deliver the same coffee experience to each customer. That, in scientific terms, means repeating every extraction yield, on every espresso brewed and served, potentially hundreds of times in a day in rapid succession.
Some of you may have seen the video published by Matt Perger of St. Ali in Melbourne or previously read the words and recommendations of Scott Rao in the Professional Barista’s Handbook. Inspired by these works, we decided to do some simple testing of our own at La Marzocco USA, in Seattle.
The testing was very straight-forward. Using a dose of approximately 20 grams of ground espresso in the portafilter1 2 3, and producing 40 grams of liquid espresso in the cup, we aimed to achieve a beverage strength of 9.25% total dissolved solids (TDS), with a resulting extraction yield of 18.5%4. The aim was to try to achieve an extraction yield that was within +-.5% of our target yield of 18.5%. (The minimum yield within the aim was 18% and the maximum 19%.)
Next, we conducted four tests:
Test one allowed for the barista to use only one set time. In this test, the barista dialed in to achieve a beverage weight of 40 grams and a yield of 18.5% in 28 seconds. Once the test began, the barista continued pulling shots exclusively at 28 seconds. “Normal”5 bar-style dosing conditions were applied in this test, and also in tests two and three.
Test two allowed for the barista to use both time and sight (visual appearance of espresso in a shot glass) to dictate when they would stop their extraction. Today, many La Marzocco USA customers train their wholesale customers to prepare espresso using this method.
Test three utilized volumetric flowmeters6, again with “normal” dosing conditions (the barista dosed the coffee going into the portafilter with a combination of grinder dose and a controlled leveling process).
Test four utilized volumetric flowmeters with a coffee dose that was controlled within a tenth (0.1) of one gram for every extraction, using a scale to weigh the portafilter prior to brewing.
Prior to each of the four tests, our barista adjusted grind and time of extraction in order to achieve an 18.5% extraction yield, using a scale for dose to 20.0 grams and separate scale for beverage weight of 40 grams.
The data was staggeringly decisive. Let’s take a look…
To view the test results and data please click here: Test Results