Once again I am forced by progress to revise my original book:” Espresso Coffee: Professional Techniques”. The impetus for this is bottom-less porta-filter techniques and theory, and the absolute perfection of steamed milk texture with Shojiro’s new steam tip, the Foam Knife 1.
What is new:
* Perfect milk foaming tool: Shojiro Saito’s “Foam Knife 1″ combined with Vivace technique results in perfect milk foam.
* Technique and theory when using bottomless porta-filters.
* Expanded latte art tutorial section with color plates of our favorite pours over the years at Vivace.
* New diagram and explanation of roasting for espresso.
The price is $34.95 plus shipping and the book should be on sale at our stores and web site within the month.
For espresso bars employing any other steam tip, and porta-filters with spouts, my book “Espresso Coffee: Professional Techniques Updated” is still current and will remain on sale.
This summer I went to Coffee Fest Seattle to compete in the new espresso contest. Although I did not place with my sweet Harrar, I found something more valuable.
My visit into the competition arena began with Signor Gianni Cassatini enveloping me with his trademark Sicilian charm, a warmth so overpowering I was convinced it must be a sales put-on, an effective mask for the man within. Months later I can tell you Gianni is a true peach, what you see is what you get, a warm gentleman that loves espresso and the people that make it. Anyway… I digress. After introductions and bear hugs…(omg bear hugs)…he said” David we put heating elements in a 14 pound brass group-head and they are PID controlled. And of course we have PID controlled boilers for each group as well”. I about died right there…’No way! My dream come true and the final piece to make the temperature perfect… I might have said…not sure because I was absolutely floored . (The diffusion block is the achilles heel of all the new PID machines…it is always under temperature and takes energy from the brewing water to come to temp in the first few seconds of the shot). The new machine is called the Aurelia.
Aurelia group head showing internal valve
Aurelia group head showing heating element
Aurelia group head showing mistake: brass brewing surface. They have taken my advice and will use stainless steel here.
I have had an Aurelia on the bar for 8 months or so at my Brix location and the coffee it makes is a whole ‘nother animal. Simply stated my Vita blend comes out with so much power in the flavor that cappuccino tastes like macchiato prepared on other PID machines. ( My Synesso still makes sweeter shots however which is interesting. Perhaps the Aurelia just needs to season.) And the crema is so thick it cannot get out of the coffee basket…yes you read that right. I have been struggling with a flow rate problem on the machine, it is either fast or drips it’s way to the finish with no in-between. After trying everything, pressure variations, changing baskets, and gigluer orifice sizes my tentative conclusion is that the crema produced by the machine and my DRM conical grinders overwhelms the basket itself. It is just too thick to escape…I’ll take it.
Controls are nice with broad buttons to activate the groups and an illuminated tray to view the shots. A light blinks above the group to remind you it is on, shot timers for each group, very user friendly. And if you want to change the temperature you can enter program mode in seconds and adjust with precision in increments of 0.4 degrees F. ..My interest is in the coffee but they have packed in plenty of the latest modern advances, with the notable exception of pressure profiling. Good job Simonelli, they ignore the latest gimmick in machine design because they actually know how to make this coffee. ( Stable pressure throughout the brewing cycle will give you the best flavor profile. Changing pressure during the extraction is like changing the temperature and will reduce flavor intensity…the two factors are intimately intertwined).
The pour: espresso Dolce 20 seconds in, DRM grinder. Color is deep and uniform comparatively
And the steam valves….these are the best I have used. You can squeeze it gently upwards with your thumb for steaming micro-quantities of milk with perfect control, or lock it down for full power. I asked Roberto, the CEO for Simonelli USA why the steam valves are so good and he replied it is because they have been working on them for 50 years. It reminded me that this is a company with some serious Italian history and I am amazed they are embracing the new world of artisan coffee with such skill and fidelity to the holy grail: perfect temperature stability. Also they are old-school in regards to the practical reliability of the machine, retaining such simple effective things as the pressure-stat to control the steam boiler and access to an adjustment to change pump pressure without removing panels.
Right now it is boxy…but I am told of sleek low frames to come for this beauty….
The range for a Brazil. Roasting lighter produces a flavor dominated by citric acid, darker and the flavor is dominated by bitterness. In between is a world of varietal notes shading from sweeter into more bittering.
ROASTING FOR ESPRESSO David Schomer, July 2012
The key to developing your espresso roast is precision feedback. The better you are at extraction the more accurate, repeatable flavor profiles you have during tasting. Of course you must perform a rigourous cupping for defects, but espresso coffee must also be tasted using the espresso method. A saturation method such as cupping brings out a different range of flavors than a well made espresso. You need to be able to accurately determine what flavors you have developed in each bean you try to master. In espresso this is a witchy prospect: consistent flavor preservation through the brewing process. But the better you are at extraction the better you will be able to detect how dark to roast each bean. (By now you know the drill on extraction: fresh coffee, sharp grinder burrs, machine is clean and tuned, and shot times of 25 to 27 seconds. For review, look at my archives at espressovivace.com or dig up a copy of my book. )
Most roasters use a cupping formula which at its essence is simple and repeatable to minimize variables affecting the result. Think of French Press without the screen. But soaking your coffee in water, no matter how concentrated you make the final brew, will not work to replicate espresso flavors. Many notes will not be concentrated enough, like being diluted by the longer soak in more water. But some flavor notes, caramelized sugars or dark chocolate for example, simply do not survive in a drip cone or a French Press. Espresso’s unique contribution to brewing coffee is the pressure and very short percolation cycle. Combined with the temperature controlled machines we live in a time when you can pull a shot that tastes as good as the ground coffee smells. But, you have to be extremely precise technically, and be working with a machine that holds its brewing temperature to within one degree F..
The way it worked for me in 1991 was to scoot down to SanFrancisco and take a roasting lesson from Robert Henley. I had learned from Ernesto Illy that a Brazil was a good variety of coffee to start with for an espresso blend. A friendly broker, Tom Kilty in Oakland was willing to supply small amounts of green coffee for my experimentation and I acquired a small supply.
I installed a probat 2-barrel sample roaster in my basement at home and begin to roast batches every day that I would take in after de-gassing and try at my cart. Robert had taught me that fresh roasted coffee loses 85% of its internal CO2 after 10 hours, but I always let my roasted coffee stand for two days before brewing and tasting. I brought each batch to my cart at 5th and Union and Jenny Vanderbeck and I would try the espresso. It was Jenny that remarked on the caramel taste coming out more with each batch as I tweaked and tuned the roast profile. It took about 2 weeks but I zeroed in on the sweetest band and moved on to a Guatemalan. I thought that if I enjoyed the Brazil at that exact temperature and degree of development maybe the Guatemalan would peak there too. It was true for awhile….
Even then I did all my sampling using the espresso method. My espresso machine was a prototype LaMarzocco Linea that I had tricked-out to hold a 2 degree F. range of brewing accuracy (instead of a six degree range), and my hypothesis seemed true: the color of the Brazil and the color of the Guatemalan were the same at peak flavor development. Later with the precision PID machines available now that hold to within a degree, my roast profiles are different for the two coffees with the maximum sweetness point emerging at slightly different roasting intonations for each bean. Precision brewing allows for precision roasting. So much so that after the development of the Synesso Cyncra in 2004 I wrote a piece that stated that this was the beginning of the era of roasting and blending in artisan espresso operations because a machine finally existed that could offer a repeatable flavor profile in the final cup. Previously we were flyin’ blind.
Vivace developed our Northern Italian roast in 1991. It is deep mahogany brown with no oils on the surface, a smell like toasty caramels and earth, and at the time people thought it was light. Lately I have tried coffee roasted much lighter with a sharp lemon taste in the shot. This article is to suggest, (and defend) limits to roasting experimentation that are unique to the espresso method. Espresso is a concentrated coffee. Some things that are desirable for drip or press brewing methods might not play well at the concentration levels found in our little dab of crema: especially citric acid. An eloquent Brazilian coffee taster I met at a show thought that a little acidity in a French press or drip coffee acted like carbonation in a drink and sort of cleansed his tongue, and ultimately assisted him in enjoying the unique aspects of each bean. I took it to heart and roasted deliberately acidic coffees of various potency for six months or so and came away totally convinced it is not good for espresso. An acid taste in the cup is composed of sugars or varietal notes are still not developed yet in the roast. It is too light. But even worse the citric acid has a destructive effect on any flavors that may have been developed-it literally destroys the fragile molecular structure of caramelized sugars or varietal flavors.
This is my attempt to depict the relationship between acidity, sugar development, and carbonization in roasting coffee.
For example, I recently walked into a new place in Fremont. It has a beautiful design and feel, with LaMarzocco Strada machines promising some artisanship to the preparation. Big name roasters had stickers on the grinders. My friend and I ordered straight shots of a Harrar they were featuring. Lovingly pulled shots were completely dominated by sour lemon the cup. ( My friend takes sugar and cream, no help. At least with burnt coffee you can get a nice flavor out of it with enough milk and sugar). I was speechless. Is this what you really want in your Harrar? I thought. Is this intentional? Later I found it is aggressively intentional. Well I thought, you just go ahead and serve that and I will just be over here with dark chocolate, blueberry, and caramel in our Harrar.
I will state here that any lemony flavors in the final cup indicate a defective espresso coffee. And of course, in Italy, the birthplace of caffe espresso, an acidic espresso is considered defective. (You may encounter acidic espresso as you approach Switzerland because they primarily have a drip coffee culture featuring very light roasts). A persistent lemony flavor in the cup through a wide variety of extraction parameters means that the defect resides in the roast. (Remember you can get lemony flavors from a sweet roast by brewing under temperature as well.) But before you strap on your boxing gloves let’s try for a little common ground.
Choosing a roast for a single origin bean is a very personal choice and should generate heated discussion about the best way to roast it. The individuality is what makes a coffee culture. (Take a look at the great bloom of craft brewers going in the US, making some of the best beers on the planet. Dozens of styles, beautiful). But, you want a Guatemalan Antigua to be recognizable and have some distinctive notes that make it an Antigua…right? Also roasters, particularly single origin espresso fans, want to taste differences in each bean…varietal characteristics imparted to the arabica coffee through unique soil conditions combined with harvest conditions including weather, and processing. This is a “given” when we approach roasting any coffee: we want to taste that unique coffee. We don’t want lemony flavors or burnt rubber.
Different varieties of coffee are usually not roasted together. We blend them after roasting each one separately to achieve the best development of that coffees varietal notes and caramelized sugars. Speaking of blending we do not sell or serve single origin coffee as espresso. The reason is the same one I laid out 20 years ago…it is boring to have only one flavor profile in an espresso coffee, like one color lights on the Christmas tree… A blend may have three to five coffee varieties in it. Some beans for power, some for sweetness and spice. Now with the precision machines we see that very small changes in the flow rate of the coffee coming out result in different flavors in the blend being prominent in the cup. The beans vie for your attention on a changing basis, different every day.
For example, our Espresso Dolce has caramel, dark chocolate, leather/salt, honey, blueberry and toast notes present in a balanced shot. But when the flow rate varies (as it almost always does), within that 2 second window of 25 to 27 seconds to pull the shot, different notes compete for dominance. If it is a little slow and short, more caramel comes out. Some shots feature more blueberry or dark chocolate. Toast is the most elusive flavor and only comes out in the most balanced shots. It is so cool hunting for the toast….The resulting experience is quite complex and beautiful day after day as espresso reveals it is even more sensitive than I ever imagined. And for me, it would be a shame to limit the symphony of flavors by only brewing one type of coffee. (Maybe “single origin Fridays” or something like that would work for us…)
In our case at Vivace we also want sweet coffee in addition to varietal flavors, and we try to roast to the peak of sweetness for each coffee we use. This is an aesthetic choice made by myself. As I have said many times, “one man’s cough-syrup is another man’s chardonnay” to indicate my attempt at broadmindedness in the face of darker roasts. This self effacing style is stretched pretty thin by the lemon coffee however.
In roasting coffee we are developing flavors in what is classified as a Maillard Reaction due to the development of caramelized sugars, CO2, and heat in the final stages. We are trying to pick off the peak of the sugars without a trace of acidity. For our roast most Arabica coffees are not suitable because they retain acidity at their peak sugar point, and bitterness creeps in before the acidity is roasted out. Most South American, Hawaiian, and many Indonesian coffees are too acidic to consider for our blend because the acidity drops away at a darker color than we use, towards the end of second crack for those coffees. . We choose our beans from coffees classified as “mild arabicas” because of their low acidity at the peak-caramelized sugar concentration. And yes, Brazils are usually good in this regard.
Another point of agreement is that as you roast darker acidity decreases and bitterness increases. (Andrej Illy “ESPRESSO COFFEE:The Chemistry of Quality”) Each single origin coffee will have a unique temperature and color point where citric acid drops off. (For my roast, Northern Italian, many arabica coffees feature acidity in the cup. So I search and sample for low acid arabicas. The darker you go the more coffees that will work for your own roasting intonation. Shopping is easier.). As temperatures rise the acidity disappears, then you have the development of varietal flavor notes and caramelized sugars. As you roast darker sugars begin to carbonize and bitterness increases as sweetness decreases. (A note about sweetness…The bitter/sweet preference in roasted coffee is perhaps quite different for different people. People from hot climates with spicy food traditions may want more bittering in the coffee, as evidenced perhaps by the darker roast as you head south in Italy). At some point, the carbonization of all the sugars dominates the coffee and all varietal flavor notes are incinerated or covered by the burnt- rubber taste. This is the limit for dark roasting espresso. When all varietal characteristics and caramelized sugars have been carbonized it is a defective roast. And when all sugars and varietal notes are in the acidic stage of development, the roast is too light and is defective, a waste of the coffee bean. In between is a world of flavor development within each bean. A world unique to yourself and your brewing acumen and technology combined.
So you have lemon acidity and burnt rubber at each end of the roasting spectrum as limits for coffee intended for espresso, and an entire world of subtle flavors and caramelized sugars in between. Andrej Illy has documented hundreds of fleeting molecular compounds that compose this mercurial shape-shifter known as roasted coffee. Find your own unique favorite intonation or each bean you use and vigorously defend it as the best way to roast that coffee. Paint your own picture between yellow and black.
Sweet espresso extractions feauture unstable crema, such as this coffee at 15 seconds after finishing.
- Crema at about 10 seconds after shot finished.
When I toured Italy in 1989 and 1991 I was reminded by roasters and food critics that one sign of an expertly made espresso was long lasting, thick crema. And at the time in our shops, crema remained thick and persistent for 90 seconds or more.
Then when we stabilized brewing water temperature to within one degree F in 2001 I noticed that along with all the sweetness we had preserved into the cup, crema became a light, delicate chiffon that dissapated quickly in the cup. If you were quick, however, it had a lovely, silky mouth-feel. Years have passed since then and I have learned that the sweet extraction we can now produce has a fundamentally different quality, probably due to the presence of the sugars. I trust it is here to stay.
Foam is composed of what are called long-chain surfactant molecules. Persistent foam is present when the molecules remain in unbroken chains, trapping the gas in the liquid. (Perkowitz “Foam”) I telephoned food scientist Carl Staub when this phenomenon first occured, and he suggested that the presence of more sweetness in the espresso might be the reason for this breakdown occuring more quickly in the crema.
It is important to consider this in enjoying caffe espresso as a culinary art, for the full flavor and silky texture: you must enjoy it immeadiately. Two quick sips from the hand of the barista, at the bar. The first sip is bracing, all the sass with lighter body, in the final sip are the sugars, which invariably sink to the bottom of the cup.
As I mentioned some years ago, improvements in espresso equipment or technique often reveal something new about the tricky coffee. Like Ukranian nested dolls, open one and, ha, there is another tiny doll. In the case of temperature-stabilized machines such as the Synesso or LaMarzocco we can see now that flow rate, the speed at which the espresso flows, acts exactly like temperature on the coffee. Fast pours, under 25 seconds, are sour just like under-temperature brewing water, and slow shots 28 seconds or more, are hollow. We kind of knew that….but the degree of sensitivity is what is so surprising.
At Vivace we pull shots in 25 to 27 seconds to reach our target volume. (Remember, establishing your own volume is an artistic choice you make for your self at your own bar, but Vivace’s double is just under one ounce now. Did someone say “ristretto”?) Within the 2 second window there are dozens of distinct espresso coffee flavor profiles, none of them defective.
In a balanced shot of Dolce I am tasting caramel, dark chocolate, leather/salt, blueberry, and toast. Depending on almost undetectable changes in the flow rate for the shot, different flavors vie for dominance. A little slower shot has more caramel. Another shot may feature more unsweetened dark chocolate or be more on the leather/salt note. Only the most balanced shot reveals the toast note. . (the notes…the notes…I must have the notes in the cremas….”The Coffee Experience”, you tube, OMG). Anyway…what effects flow rate?
1. The grind of course is first and foremost. Not only the coarseness but the particle mix. (See micro-particle blog).
2. Packed volume for the shot- dosage. (This is one of the things we work at the hardest at Vivace).
3. Pump pressure. On almost all machines there is one pump for all three groups. So as you activate group #2 with one running pressure drops 1/2 bar or more. Mark has created the Synesso Hydra, his new machine with a dedicated pump for each group head, eliminating the problem. However, you should still operate out of a static water tank to eliminate changes in the incoming water pressure which will be passed on through the pump to the coffee.
There has been some good work done on using digital refractometry to asses total dissolved solids in coffee. Naturally I was curious to see if a refractometry index (RI) reading could actually be a use ful number to asses the quality of espresso coffee.
I bought the Atago Pal 1 and read up on it. Refractometery is the measurement of how much light is absorbed by your sample. For wine making they measure grape juice and a high number correlates to a high sugar content, measured in “brix” units. Hence the term, “brix meter”. However, that has no bearing on the instruments usefulness to measure sugar content in coffee. For example, if you measured a sample of India ink it would read 100 because it is very dense and blocks all the light from passing through the sample.
I went to work measuring the RI of many espresso shots, both excellent pours and highly flawed shots. Remember that excellent to me means that the shot preserves the fragrance of the ground coffee through the brewing process to be enjoyed as a flavor/aroma sensation. Here is the test data:
1. Espresso Dolce, ristretto pour prepared with 17 grams of freshly ground coffee and extraction time of 25 to 27 seconds. Flavor profile is caramel, leather, toast, dark chocolate cocoa powder, with blueberry notes. RI= 32.2 (average of about five shots, high 34.0 low 30.2)
2. Stale Espresso Dolce, same pouring parameters. Flavor profile metallic/ vinegary. RI= 31.0 (two shots 28 and 34)
3. Espresso Dolce ristretto prepared on a flat burr Mazzer (all other work on conical/flat DRM grinders) Flavor profile, thinner but similar to #1. RI= 28.0 (two shots, 26 and 30)
4. Espresso Dolce ristretto , prepared with 200 degree brewing water instead of 203. Flavor profile sour/astringent. RI= 28.0 one sample
5. Indian varietal ristretto, Northern Italian roast (my usual roast). Flavor profile, very sweet caramel. RI= 31.0 one sample
6. Indian varietal same as above, ristretto, very dark roast, oily beans. Flavor profile, burnt rubber, bitter. RI= 30.6 one sample
7. Espresso Dolce lungo pour 3.5 oz. in 25 seconds. Flavor profile, thin metallic, slightly sour. RI= 20.7 one sample
It is easy to conclude from this brief study that flavor development and integrity to the fragrance are not measured in any way using digital refractometry. The only interesting finding is that a coarser grind, yielding 3.5 oz liquid in 25 seconds, reduces the measured RI. This tentatively supports the assertion that digital refractometry might be a useful way to measure total dissolved solids in a brewing method. So perhaps it is useful as ameasure of brewing efficency but will not tell you anything about the flavor profile.
Often I have written about how small business is so tough it will polish you to your best self, or grind you up. And, in twenty four years it provides ample opportunity to run smack into your limitations. Now in my case I’m a wee bit of a hot house flower and I wilt in the presence of excruciating detail or repetitive managerial tasks. So, I have major help. It has been my extrordinary good fortune to have Geneva Sullivan as my partner. She is my front line general in the war against entropy that is the daily reality of a coffee business. (If it was just me I would be one small shop with very arty espresso but constantly running out of napkins or the teeny light bulbs that go under the bars.)
Geneva is a founding partner at Vivace, having listened to my schemes for improving espresso since 1988. We got to know each other doing arabic belly dance gigs together with me on flute, Geneva doing cabaret as well as ethnic classical dance. She is a natural performer with a beaming, happy stage presence.
The front line on accounting, inventory, and computers is bravely held by Geneva. When we met she was a main frame computer repair technician at Unisys, working nights and arriving on jobs where the CEO is leaking money at $500,000 dollars per hour because the system is down. This was at a time when hardware repair had the whiff of a male hegemony and she would have to prove herself again and again. Usually in two hours she had them eating out of her hand. To say she has moxie is to refer to Mozart as a piano player. She also worked at Digital before joining Vivace full-time in 1991.
During this early time she earned a degree in vocational education at night by commuting all the way over on Bangor Navy base on the Olympic Peninsula. She finished, while working, and assisting in the beginning of Vivace. Might I just add serious work ethic to the moxie mix…one descriptive quip I have always liked is to say that if I was going to get stuck on a desert island with one person, it would be Geneva because we would make it back alive.
And over the years I have learned a lot about the nature of intelligence from her. Im all flash and bang, making intuitive leaps, and abohring process, a fire mind. Geneva is a stately intellect seeping into every aspect of a problem at her own pace, and illuminating each corner of complexity in an operation or process until it comes out whole and finished. We like to call it her water mind. And it is very formidable.
Recently she created a program to calculate what effect any price change on any item we sell, would have on the bottom line at the end of the year. Her program employs our actual sales hsitory to isolate the effect of, say, raising the price of a short Americano by 15 cents. So if we have to raise prices we just plug in options and tune until cost of goods sold and net profit line up exactly where we want them to be. In an early audit by the State of Washington resulted in a $100 refund for Vivace and the auditor pronounced us as one of the most organized small businesses they had ever reviewed.
Her nickname at work is “Hurricane Geneva” for the sheer energy she brings to any project. And of course, to improve a workspace or a system, you need to tear it apart first.
After twenty years of roasting and blending I feel that this year’s Espresso Dolce has all the elements I am seeking, balance, sweetness, and complexity. Please allow me the conceit to label it myself as my opus, the best art I can do.
In tasting, the perfectly pulled shot of this blend reveals salted carmel, and toast over a dark chocolate base, with leather, blueberry, and a spice note up high like Cascade Hops in the finish.
Call “1 800 get some”…..just kidding but my web site has it
Micro-Particle Migration in Conical Grinding Systems
Let me start with an unusual apology this time….A few years ago I announced that I was partnering with LaMarzocco to design a direct dosing, conical-burr grinder. I am very embarrassed to admit that we failed to produce any machine. The “S-Grinder” project has ground (hee-hee) to a halt. LaMarzocco and I parted company on the issue of micro-particle control in the dosing system. They took the approach of eliminating static, I favor managing the coffee powder so static cannot affect the micro-particles.
Here is some background: It is well established that grinding coffee with conical grinding burrs(or mixed-burr systems such as the DRM) produces micro-particles along with larger flakes of ground coffee, macro-particles if you will…. The heavy vanes of the conical burr compress the beans until they shatter. An “exploding” bean produces all sizes of particles to enter the fine burrs for shearing. The smaller particles, pass through the shearing and make it into the powder. Then, during extraction, some of the micro-particles actually make it into the cup, giving the espresso made from conical grounds a heavier mouth-feel and more pungent aroma/flavor characteristics. So our choice at Vivace has always been conical burrs for espresso.
However, the beneficial micro-particles present us with two broad sets of problems: controlling the flow-rate of the espresso as it oozes into your cup, and preserving the integrity of the mix of micro and macro particles through the dosing process. (In the interest of scientific rigor, I admit that all my conclusions are based on the DRM mixed burr system, but I believe the following pertains to pure conical grinding heads as well.)
When the barista hits the switch and pressurized water begins to percolate through the packed coffee, it begins to carry micro-particles with it. Towards the end of the shot these particles can form a mat across the bottom of the coffee basket and slow down the flow-rate of the espresso entering the cup. And as you know, with the high-tech, temperature stabilized espresso machines, such as the Synesso, controlling the flow-rate has become even more critical to capturing the fragrance with any fidelity. Preparing espresso with conical burrs make the control of flow rate more difficult for the barista on the bar because of the micro-particle migration within the packed coffee..
Coffee ground with a flat burr grinder. (Magnification is x60, Mazzer M-100)
Coffee ground with the DRM conical/flat burr grinder. (Magnification is x60) Micro-particles are visible between larger clumps.
Note: The grind on the machines used for comparison was set to achieve the same flow-rate for the espresso. It is interesting just how different the particles are in each photo.
(It used to be, on the “old-tech” espresso machines where temperature wandered around a five degree range that shots from 24 to 30 seconds were all OK, never great. With precision temperature control, shots less than 23 seconds are sour-astringent, and shots over 27 seconds are hollow, almost flavorless. In our system, the best shots tend to pinch off just as the volume is reached and begin dripping between 22 and 25 seconds.. Shots that fall into the 25 to 27 second range, have dozens of flavor profiles. None are defective, hollow or sour, but within the range of acceptable there are so many different espresso coffees. Shots brewed for 27 seconds tends to be heavier on the carmelized sugars but with less varietal nuance. Shots brewing for 24 seconds feature a lighter body and perhaps more varietal nuance such as hopiness from the Brazils or blueberry from the Ethiopian. Ahh, but Vita shots that are in the bull’s eye, (25 or 26 seconds to reach our volume) taste of caramel, toast, blueberry, dark unsweetened chocolate, hops, leather and salt…each flavor competing for your attention in the aftertaste. A perfect balance of these flavors is very rare, and usually one of the varietal flavors becomes more prominent with minute differences in flow rate.
In fact, flow-rate, temperature, and pressure are a intimately connected when it comes to seducing the fragrance into a cup. If the temperature is a little low, say 201 instead of 203, and you extraction time for a shot is 25 seconds with pump pressure at nine bar, you get sour/astringent flavors from a Northern Italian roast. Similarly, if the temperature is right at 203, pressure is nine bar, but flow is fast, say 22 seconds to hit your shot volume, viola, sour astringent. And, if pump pressure is low, say seven bar, and flow rate temperature are spot on you have the same defective espresso: sour/astringent. )
Dosing the Powder
The Italian dosing hopper has within it an impeller system that forces the grounds through a small apeture into the dosing hopper. It is a series of paddles mounted on a flat disc, that spin within a circular chamber around the burrs and impact the coffee in a few milliseconds after it exits the burrs to push it towars the apeture. The effect is to grab the powder in a gentle clumping and once fixed, the distribution of micro and macro particles is preserved. (I really do not know if this is a happy accident or if Italian engineers were aware of particle migration).
However, if a grinder design is attempted to eliminate the clacking doser mechanism you must avoid “free-fall” of the powder. If the coffee is allowed to drop in a “cloud state” without being clumped, even for less than one second, the micro-particles separate and begin to migrate towards any metal surface. The resulting powder, lacking the micro-particles, makes a sickly-yellow espresso without full aroma and flavor.
To address this problem and eliminate the Italian dosing hopper you need to retain the paddle system to impell the ground coffee towards the apeture and into the doser. But that is not enough by itself. About a year ago after giving up on Marzocco I took it upon myself to modify our fleet of DRM grinders. I followed the lead of Malkoenig and Mazzer, and combined a simple polished cone with a wire mesh screen on the exit from the apeture leading to the grinding head. . I found that without the screen the coffee sprayed out of the grinder and micro particles adhered to the vertical, stainless steel wall.
If coffee "sprays" out of the apeture into the cone, the smallest particles adhere to the side of the cone due to the effect of static electricity
This is the coffee that is clinging to the cone on the left. (Magnification is x60)
Simple two-wire grate provides just enough back-pressure on the ground coffee exiting the apeture to gently hold the micro-particles in place within the powder. It tumbles straight into the porta-filter.
Ground coffee pushed through the grate retains it's even distribution of micro and macro-particles.
(It is worth noting that micro-particles can migrate within the powder without sticking to the wall of the doser. The problem can be very subtle and requires a barista that really knows the coffee to detect when the migration problem is slight.) But with a wire grate the powder featured a very nice consistency and tumbled straight down the cone, into the porta–filter. I had to play with it a bit. At first I begin by installing a three wire grate, (two vertical and one wire horizontal in a rectangular apeture of about 1.5″w x 1″ tall) and got very cakey, hard-powder clumps. I then tried two wires and the powder became perfect. This back-pressure gate is the key to allowing the powder to tumble into the porta-filter, through a polished cone, with no particle migration or sticking to the side.. In fact you are tuning the powder for optimal density and manageability. Too much back-pressure and you get dense “caking” of the powder. Too little back-pressure and it can spray in low humidity conditions.
How Does It Work?
We have used the system for over a year with the simple two-wire gate pictured and a couple anomalies appeared. First, we learned that if the grinder burrs get dull the powder enters the hard cakey stage. Easy to fix with new burrs. But we also have a wee mystery…the grinders enter the cake stage on their own for no apparent reason. They will cake-up for 20 minutes, then resume delivering a beautiful consistent powder And this certainly bears out what I have learned in the last four years. Espresso is infinite in it’s complexity but grinding is easily the most complex part of the lovely process. And in this case, I think the machines might be accumulating micro-particles in the paddle area, due to wide manufacturing tolerances creating gaps. Then these particles break loose and clog the chute leading to the dosing cone like point release avalanches….maybe…
Something new under the sun…the “Foam Knife One” from Espresso Parts NW is a steam tip with a slit on the end, about 6mm in length, and a 1.2 mm hole in the center of the slit. It fits on LaMarzocco and Synesso machines. I recieved it in a sample pack of three innovative tips and it is the best tip I have ever steamed milk on.
In my micro-pitcher (1/3 L) I was able to foam very small quantities of milk with the best texture I have ever gotten off that wand. It is my training station at our Brix location, I steam there every day and this tip produced the the finest foam texture I have ever seen come off that wand.
Thanks to Terry Z. and Espresso Parts NW.