Espresso… is it ambrosia or a test of endurance?
For espresso to be worthy for the gods, everything upstream must have been done flawlessly. From cultivation, harvesting, drying, milling, to storage, transportation, and roasting the standard of care must be meticulous.
And if it was all just so, then an experienced barista can coax a mind blowing drink into the cup. It will be syrupy in texture, have creamy mouth feel, and an orchestra of aroma and flavours from approach to long aftertaste.
A great espresso should not require any sugar or milk but will be delicious to sip on its own… like an excellent whisky can be.
Espresso is not a roast level, nor a grind, nor a kind of coffee bean. It is a method of preparing coffee.
At its most simple, espresso is a method of preparing coffee that extracts coffee oils under pressure.
According to the Specialty Coffee Association “Espresso is a 25–35ml (.85–1.2 ounce [×2 for double]) beverage prepared from 7–9 grams (14–18 grams for a double) of coffee through which clean water of 195°–205°F (90.5°–96.1°C) has been forced at 9–10 atmospheres of pressure, and where the grind of the coffee is such that the brew time is 20–30 seconds. While brewing, the flow of espresso will appear to have the viscosity of warm honey and the resulting beverage will exhibit a thick, dark golden crema. Espresso should be prepared specifically for and immediately served to its intended consumer.”
So how can an experienced barista prepare perfect espresso every time?
I break it down to: equipment, choosing the best coffee, setting the grind, setting the dose, tamping, observing and, most of all, knowledge and attention.
There is a lot of discussion about coffee equipment, but at its core, an espresso machine needs to maintain the temperature and the pressure of the water as it extracts the coffee. This needs to be paired with a highly adjustable grinder. Cleanliness is an often neglected factor at the peril of the perfect espresso. Coffee oils go rancid over time!
In our lab we use Synesso espresso machine because it maintains the temperature of the group to within 1/10 of a degree at all times thus offering phenomenal consistency. Having said this, I can get a decent shot out of any well maintained commercial espresso machine. The Synesso just makes it easier. I do recommend choosing a machine with a pressure gage. The pressure is maintained by a standard external pump that must operate between 8 and 10 bars. I set mine to 9 bars.
A good quality grinder with highly adjustable grind and dose are required to make great espresso. Ideally the grinder will be infinitely adjustable, meaning the burrs are adjustable by turning in a thread rather than by step adjustments. This makes it possible to maintain a constant tamp and dial in the best grind setting. If the grind is too coarse, the coffee will pour too fast under a 30lb tamp and will taste sour and under extracted. If the grind is too fine, the coffee will pour too slowly under a 30lb tamp and will be bitter and over extracted. An infinite adjustment provides the fine control needed.
Timed dosing is a great feature for consistency. The dose needs to be monitored as the volume and weight of coffee drifts across coffee batches and over weeks and seasons. We use a Mazer dosing grinder.
Tamping is arguably the most fundamental skill of the barista. A good extraction depends on a solid tamp of about 30lb of pressure to compact the coffee grinds. The compacted coffee grinds provide the resistance to the hot water under pressure so that the extraction time and extraction consistency throughout the coffee are optimal.
A quality, correctly fitting espresso tamper is essential for this. The base of the tamper must match the size of the espresso filter basket.
There is much debate about the curvature of the tamper base. I prefer a flat base so that when the hot water hits the coffee it expands uniformly up to the group head screen.
To prepare the perfect espresso, the barista must ensure the quality of the coffee. But what does this mean?
Espresso may be prepared with any coffee you choose, but generally, beans for espresso are blended to have “good characteristics” when prepared as espresso coffee. “Good characteristics” include having interest throughout tasting… from the approach through the finish or aftertaste. It should express interesting flavours, have good aroma.
The texture should be creamy and show about half crema.
It should be delicious when prepared as straight espresso, americano, or milk based drink like cortado, cuppancino or latté.
When prepared as an americano, the crema should float on the drink for a few minutes. The aroma with the crema might be different than when the crema dissipates, but both phases of the drink should be delicious. I often find that an americano has an unpleasant aroma until the crema dissipates. This is usually the expression of a roasting fault.
Espresso should also make delicious milk based drinks like latté and cappuccino so should be complimentary to the milk.
Finally, the coffee must be freshly roasted. See our post on coffee freshness here.
Ok, we have the equipment and the coffee. Now what?
Referring back to the SCAA description of espresso, we see several ranges for: water volume, coffee dose, temperature, water pressure and extraction time. These ranges indicate tolerances. It is not true that any combination of values within these tolerances will make a great espresso. Intuitively we can imagine that taking the low end of volume and the high end of coffee dose might not be the best combination.
It turns out that there is a sweet spot within these tolerances and a senior barista can find that wandering sweet spot and maintain it throughout a shift and find one again under any conditions (providing the equipment is in good order).
So the challenge for the barista is to ensure consistency of the factors that are controllable. The factors while preparing a drink are coffee compaction and distribution, temperature stability, and cleanliness.
Compaction and distribution are a function of dose, dose distribution, grid size, and tamp. As mentioned above, if the doser is set within the 7g-9g range for a single, it can typically be considered a constant over the time of a shift. The dose distribution is the density of grounds throughout the filter basket. The coffee should be evenly distributed. Tapping the side of the portafilter prior to tamping can redistribute the grinds evenly.
Then the tamp, solid and directly downward. The tamp should be level. This is much easier in a bottomless portafilter than a spouted one and we recommend bottomless portafilters. They are also much easier to keep clean… and watching the pour is so pretty!
The old practice of twisting the tamper with pressure creates fissures that allow “tunnelling”: water follows the fissures resulting in uneven extraction throughout the dose. So does the old practice of knocking the side of the portafilter to remove loose grinds. Instead, use a brush around the edge of the portafilter.
When tamped, the level of coffee in the filter basket should be near the fill line. Visually monitoring this can indicate if the dose has wandered. If the coffee is distributed evenly and the dose is right, coffee will expand to fill the filter basket thus creating the needed resistance to the water flow. The spend coffee forms a solid almost dry puck and will show the impression of the group head screen.
The biggest mistake I see in espresso preparation is focusing on one metric at the expense of others. I recall watching my drink being prepared and watching the barista weigh the portafilter full of coffee several times adding coffee each time to get the weight exactly 14 g dor a double. Meanwhile the portafilter lost all of its heat. The drink was not good because the attention to the exact middle of the weight measure range was pursued at the expense of temperature stability. The water hit the cold portafilter and did not extract properly.
Instead the barista should have set the dose, either by time or volume and made micro-adjustments to the grind setting to keep the pour timing in range.
Finding the sweet spot is what great espresso preparation is all about. And the result is measured in pleasure.