Dosing Debate, Public Forum

Just picture scorecards speckled with espresso drips and how you would feel after test sipping 20 shots of espresso. And we decided to swallow, not spit. So yeah, the buzz was intense. Especially at 8:30 at night...

Last week we conducted a carefully controlled espresso dosing experiment at the Phoenix Roastery. We investigated which dosing method (dosing refers to the way the barista fills the portafilter basket) gives the best results. We are in the process of switching to all La San Marco two group machines at our stores, and the new portafilters have differently shaped baskets from our previous machines, which is how this question arose in the first place.

The "new" dosing method proposed by Dennis Skitzki, our espresso wizard, is that we fill the dosing chamber with ground espresso and adjust the dosing mechanism in each grinder to dispense precisely 8.5 grams of coffee per segment of the dosing star. The dosing star is the star-shaped divider inside the dosing chamber that parses measured amounts of coffee down the hole (from where it falls into the waiting portafilter) as it rotates with each pull of the dosing lever on the side of the grinder.

The status quo dosing method (previously espoused by the same espresso wizard) is to overfill the portafilter basket and level the basket off using a finger or the lid of the dosing chamber, much as one would measure flour in a bakery. The portafilter is essentially being used as the measuring cup.

Potential problems with the latter method are consistency of leveling and how many times the barista drags the coffee partially across the portafilter before leveling completely. Not to mention that with the La San Marco machines, this method results in more coffee in the basket, which is not necessarily a problem, but it will result in a slightly different grind size.

At our investigation last week, first we had different baristas dose ten shots worth of espresso and we weighed the dosed amounts on a gram scale. This is a very simple exercise, but very interesting. The two most consistent dosing methods were me (SWJ) using the dosing star technique, (.18 standard deviation) followed by Kim, the manager at the Superior Cafe, using the level dose method and the lid of the dosing chamber to level with (.25 standard deviation).

The second round of the investigation consisted of barista Stephen Shaum pulling 20 shots, randomly alternating between dosing methods, and therefore grind size and coffee amounts, and having a panel of judges rate each shot. Ten of the shots were prepared using the level dose method, and the other ten were prepared using the dosing star method. The judges couldn't tell which dosing method was used for which shot, so it was a blind taste test from that point of view. Flavor wise, the level dose shots got an average score of 7.183 with a standard deviation of 1.1 and the dosing star shots got an average score of 7.003 with a standard deviation of .88.

We didn't feel that the difference in the flavor ratings were statistically significant. But we did observe that since we threw out any shot that was not in the 20-30 second range, it was considerably more difficult to produce an acceptable shot on the level-dose machine. Also, there was about a pound of wasted coffee around that machine by the end of the night, versus about a quarter pound of wasted coffee around the grinder that dispensed coffee using its dosing star.

Overall, I would say at this point that I am sold on the dosing star method, due to less coffee waste and comparable taste and comparable consistency results.

But Wiggles (barista at the Coventry store) still says that the dosing star has no soul. That method gives the barista less control over the pulling of the shot. Which is why this issue has become so hotly contested! Isn't soul the most important thing in a shot of espresso anyway? I still think that's why espresso is amazing; it gives you a flavor window into the barista's soul instantaneously. If they're on their game, the espresso is good, the soul is good, life is good. If they're off their game, their spirit is crushed, well, the espresso is also.