Espresso Coffee: a Complex and Fragile Beauty

davids_13by David Schomer

Often during my twenty years spent in hot pursuit of this elusive espresso, I have come back to the words of Piero Bambi, the owner of LaMarzocco espresso machines: ‘In espresso we are trying to preserve the fragrance through the brewing process’. And really, isn’t that what anyone wants from coffee, to taste as good as it smells?  But to achieve this is to control several complex factors from the green bean selection, roasting, and blending to the sensuous performance art of brewing and pouring. Let’s follow our barista as she performs her graceful dance to lure this delicate beauty into a cup. It starts when she (we are tagging along with Linda Cleckler) hits the button on the grinder. Heavy conical upper burrs pull the beans down, compressing them until they shatter into smaller fragments to enter the flat burrs, to be sheared into the final grind…  
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Seventeen grams of the fluff exits the edges of the flat burrs and drops into a chute along the sides of the grinding head. A whirling brass paddle smashes into the coffee, whisking it on a furious circular journey at about 450 rpm until it is forced out a square portal to tumble into the dosing hopper. After grinding, this is the first real assault on our sweet coffee – the impeller smashing it into lumps, bruising the lipids and destroying a little of the fragrance. 

Linda begins flapping the vestigial Italian dosing lever and in little pie-shaped chambers the coffee advances towards an aperture in the floor of the hopper to drop into her coffee basket. For the Italians, one pull on the lever gives a single shot, two pulls delivers a double dose of ground coffee. I describe it as a vestige because we grind only by the cup and achieve portion measurement with a timer. The Italian dosing hopper is also somewhat of an air and coffee mixing machine, and oxidation claims a bit more flavor. But these flavors do not go quietly into that good night: oxidation, literally the bonding of an oxygen molecule on the molecular structure of the aromatic compound, creates a sour/astringent flavor, and aggressively degrades the sugars and aromatic oils in the cup. Because of the short, pressurized percolation cycle of around 25 seconds, the final consistency of the ground coffee is critical to achieve crema, and preserve the full amount of fragrance the bean has to offer.

 

 The flat burrs shear the bean into a complex consistency that looks like snowflakes under a microscope. To accomplish this the flat burrs must remain very sharp and require changing every 500 pounds. The goal of the grind is to achieve the highest surface area of exposed aromatic oils, lipids and sugars to be transported quickly by the brewing water into your cup. The rapid percolation cycle and pressure are the unique characteristics of the espresso method that allow us to preserve the most delicate fragrance through the brewing process. With such a short brewing cycle, the grinder is the critical machine to preserve the highest percentage of the fragrance per gram of coffee used. However, the espresso machine is ultimately responsible for the integrity of that fragrance – in other words how closely the flavor resembles the fragrance.

 

Linda, of course has infinite capacity to destroy the coffee as she doses, packs and locks the porta-filter into the group head of the machine. Or, with finesse and skill (which is the case here), she can be the maestro that brings the entire symphony together. A great barista takes years to master the nuance of temperature control, particle distribution and packing, the espresso flow rate and the cleaning regime to make a distinctively superior espresso. She is in her fourteenth year as a pro barista.

 

In Trieste, Sergio Michael of Illy Caffe told me they consider the ‘miscela, mano e macchina’ or the blend, the barista and the machine, as equally balanced  factors to create (or destroy) a fine espresso. It was during my visit to Illy in 1989 that I truly fell in love with the sweet Northern Italian espresso roast, a roast simply referred to at Illy Caffe as “normale”. So, before she hits the brewing switch let’s talk about the roasting of coffee for espresso.

 

coffee-beans_smallThe picture shows three roasts with the darkest being found in Naples, located in the southern half of Italy. The medium roast is representative of coffee found in Florence and the Central Italian style, and the Northern Italian roast might be found in a typical espresso bar in Milan. 

 

Roasting is a Maillard reaction (so named after the French chemist Luis-Camille Maillard, credited with classifying this class of reactions in 1912) and produces CO2, caramelized sugars and heat in the final stages.  Darker roasts than the Naples example in my opinion are outside of our consideration for the caffe espresso method. The carbonization of sugars makes a pronounced bitterness in the espresso in very dark roasts. Again we go back to the simple essence – just smell the coffee and it is very apparent what its flavor potential is (if it smells like burnt rubber perhaps it is not so sweet).

 

The Italian lore acknowledges that as you travel south the roast deepens from Northern Italian and begins to become darker in color. As the final color becomes darker, acidity decreases, while bitterness increases in the final cup. I would add a corollary to that maxim: the darker that you roast the more consistency that can be achieved in the flavor of the espresso. The most difficult roast to brew consistently is of course, the sweetest, fresh Northern Italian roast. Darker roasts are achieved by stopping the roasting process at a higher temperature where complex sugars and aromatic oils carbonize. If you go very dark, 100% of the fragrance has burned up and these molecules are very stable. This results in an easily repeatable, but fantastically bitter espresso coffee in the cup (hmmm… I suppose, if we added enough milk and sugar…)!

 

I have chosen the Northern Italian style for Vivace because it is roasted just to the peak of caramelized sugar content, and quickly cooled. (Forceful cooling is essential or the beans will continue roasting without added heat and left unchecked can actually result in the coffee catching fire in the roaster). But the sweet roast demands the very highest attention from the barista and roaster because of the very high concentration of sugars and aromatic oils, which are the fragrant molecules that are the most volatile. The fragrance is an earthy caramel with a slight toast/leather note and traces of dark chocolate and blueberry.

 

Oxidation, incorrect brewing water temperature, an incorrect flow rate or a dirty machine are going to cause the most noticeable deterioration in this style of roast compared to Central or Southern Italian roasts. For the restaurant owner I recommend the Central Italian degree of roasting as a good compromise between sweetness and volatility. The sweet roast will drive you and your staff nuts… I promise. Once roasted, coffee should be stored in a cool dark place and is best on days four through eight after roasting. Any artisan roaster worth considering will put the roasting date on the package.

 

Back to Linda, and our perfectly ground, dosed, and packed fresh coffee, as she turns on the brewing switch in the espresso machine. Her action opens a solenoid valve and turns on a rotary pump at the same time. Water held at 203 degrees F. surges against a 0.6mm carburetor jet placed inside the water line right above the group head. The machine engineers have chosen the faintly suggestive term “gigueler orifice” to refer to this important restrictor in the flow of water to the coffee. The purpose of this is to create a chamber between the tiny pin point, madly shooting hot water, and the surface of the coffee bed. This pre-infuses the coffee with brewing water because it takes between one and two seconds before the chamber between the coffee bed and the jet fills, and the coffee feels the full pressure. The gradual build up of pressure prevents pressurized water from fragmenting the top of the coffee, and loosens up the flavors in the top layer of the packed coffee. The whole cycle takes about two seconds.

 

Linda has started steaming the milk, first stretching to add air, then submerging the steam tip and locking into her whirlpool to create the chiffon texture. In seconds two through eight, the water rapidly percolates evenly through the cake under 125 pounds of force. Inside the pressurized chamber, caramelized sugars, lipids, and hundreds of varieties of fragrant molecules are trapped in dense foam – the crema, and quickly transported into your cup. The speed, and the cradling of the volatile oils in the crema, is responsible for the espresso method offering a flavor/aroma experience that has the highest fidelity to the true fragrance of the roast.  Longer saturation methods, such as French Press or Clover, will never preserve the finest flavors the coffee has within it.

 

davids_7During seconds eight through twenty three, the beautiful red-brown crema oozes into the cup. The total volume of our shot, made from 17 grams of coffee, is less than two ounces. The shot is usually brewed into the porcelain cup it will be served in to avoid losing crema by transferring from a shot glass into a cup. Linda turns off the pump. If her milk is not ready to pour she adds a bit of “saver milk” to preserve the crema. Crema is a polyphasic, colloidal foam according to Dr. Petracco of Illy Caffe. Polyphasic, because it is changing very rapidly in your cup, colloidal because there are particles suspended in liquid, and foam of course is gas suspended in liquid. Within moments of brewing the dissipating crema can release much of the more noble flavors and begins to lose the satin-like mouth feel.  

It is carbon dioxide that makes the foam in espresso (remember your Maillard reaction). The particles in espresso are tiny bean fragments and microscopic droplets of the oils. These are the real tasty bits. The aromatic oils are too numerous and fragile to measure. The latest attempts by Italian chemists put the number of distinct compounds between 250 and 800; for a complete analysis I recommend the ‘Chemistry of Quality’ by Andrej Illy). When perfectly fresh, the crema creates a downy-silk mouth feel and harbors the sugars and aromatic oils for just a moment, to be savored before burning up through exposure to air. After the aromatic oils, sugars and gas, crema is also composed of water. It is worthwhile to step back and consider water. 

 

In Seattle, our water usually has around 50 parts per million (ppm) of total dissolved solids (TDS) You can think of TDS as mineral content, also referred to as hardness. Seattle, with fresh mountain run-off as a water source has very soft water. A little more hardness, right around 150 ppm of TDS, will give espresso, or brewed coffee, more depth of flavor and a deeper development of distinct varietal flavors, such as dark chocolate and blueberry notes present in a fine Ethiopian Harrar. This ‘tuned’ water will also remove a persistent, slight metallic note in the coffee. This water also has a very similar effect on the finest maccha. Maccha is green tea made only from the highest grade, shade grown ‘baby’ tea leaves, and is prepared with a whisk in a very strong concentration. Espresso can be compared to Macccha for its body and mouth feel combined with a very concentrated flavor.

 

The Persistence of Crema

One great joke on Vivace has emerged from our twenty years of efforts to perfect caffe espresso: the more caramelized sugars we preserved through brewing, the more fragile and delicate our crema became. It seems that sugars have a damaging effect on surfactant molecules responsible for foam. Crema used to last much longer on top of the shot than it does now.  I would welcome collaboration with a food scientist to explore this problem. Linda is finished steaming just as the shot is ready. This timing gives us what we call high definition foam for very sharp latte art. For best mouth-feel we steam first and swirl the pitcher as the shot comes out. The milk will take on sheen like white chrome and the mouth feel takes on a more velvety texture. She is ready to pour.

 

She pours with total focus. Starting out she tilts the cup and positions her pitcher right on the rim of the cup. She pours close to the surface of the coffee and with a slow flow rate of milk from the pitcher.  The idea is not to disturb the crema in the beginning of the pour. When the cup is about half way full she pulls the pitcher back, always pouring, and it sways like the head of the cobra looking to strike. Then, she strikes…sweeping the pitcher back towards the surface of the coffee she also begins pouring milk faster. The pouring speed combined with the sudden motion creates a current within the cup that speeds to the back and splits, sending the flow back along each side of the cup towards her hand.

 

Into this current she casts ribbons of milk with a gentle undulation of the pitcher. The white ribbons flow to the back of the cup and are swept back up each side towards her hand. With great artistry she creates the shapes she desires and then when the cup is full the flow rate of the milk is reduced to create a pencil point. This is the “scribe” used to draw the stem, or the split in the heart. At best the latte art captures the flow of milk and espresso combining in a still image. They are beautifully impermanent; the instant it is poured the foam begins to coalesce, slowly losing mouth-feel and sheen… Hopefully the customer enjoys it at its peak.  Then, the dance begins again.

 

Author David Schomer is the co-owner of Seattle’s Espresso Vivace.  For more info. please visit www.espressovivace.com

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2 Responses to “Espresso Coffee: a Complex and Fragile Beauty”

  1. cafedave.net » what happens when an espresso is made Says:

    [...] magazine] Beautiful description of the espresso preparation process. This entry was written by dave, posted on Today at 5:56 am, filed under coffee-life. Bookmark [...]

  2. Coffee Appreciation - Page 56 - London Fixed-gear and Single-speed Says:

    [...] Originally Posted by Brave Question for anyone but I have a feeling bomcup will have the answer. Why are some beans shiny, shiny black (and almost greasy to touch) and some a matt, coarse brown.. I figure it has to do with the roast but how and why.. And is one bad one good or make no difference at all? The picture shows three roasts with the darkest being found in Naples, located in the southern half of Italy. The medium roast is representative of coffee found in Florence and the Central Italian style, and the Northern Italian roast might be found in a typical espresso bar in Milan. http://www.bestcafes.com.au/espresso…fragile-beauty [...]


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