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  • The Dynamics of Espresso - Robusta: Friend or Foe?

    Posted on January 13, 2013 by vyee

    Robusta: Friend or Foe?

     

    Robusta Quality: A Paradox

     

    Call me a coffee heretic, but I happen to think high-quality Robusta coffee beans add an important taste dimension to espresso. Virtually every Italian roaster uses some Robusta beans in their espresso blend. In North America, it’s conspicuous by its absence, and I think the North American espresso drinker is generally the poorer for it. Let me explain.

     

    Almost no one outside of Italy understands (or wants to understand) how to use Robusta coffee as a component in their espresso blends.

     

    How is it that the North American specialty coffee industry has mostly turned its back on nearly a hundred years of Italian espresso wisdom?

     

    Part of the answer lies in the different methods of preparing coffee between North America and Italy; Pourover, drip, and French press methods (non-pressurized) are completely different from brewing espresso (pressurized).  They are as different as using a barbecue and a pressure cooker for cooking dinner. In North America there is different history that also factors in.

     

    Before specialty coffee, there was supermarket coffee. Sold in cans and brick packs, this market was controlled by large industrial coffee roasters (Maxwell House, Folgers, Nabob, etc); coffee that was sold on low price and low price only. Low quality Robusta beans cost less than the equivalent lower quality Arabica coffee beans, and so they formed a large part of the blend (a few roasters even managed to add chicory). During this time (the 50’s and 60’s), the percolator was the popular brewing method and cream and sugar were routinely added to make the coffee more palatable.

     

    In the 70’s, the specialty coffee industry was born. Starbucks, Peet’s and Stewart Brothers coffee (now Seattle’s Best Coffee) in the US, and Timothy’s Coffees of the World and Second Cup in Canada and others, all started up. These specialty roasters and retailers were the antithesis of the price driven, mass market supermarket coffee – they featured single origin coffees from (at the time) exotic locations with exotic names –Mocha South Yemen, Ethiopian Harrar and Guatemala Huehuetenango to name only a few. All these coffees were 100 per cent Arabica and tasted great in comparison to the supermarket offerings (especially in the then new drip coffee makers) and quickly gained a loyal following.  Of course, it didn’t hurt sales that they were often advertised as 100-per-cent Arabica, no Robusta!

     

    In the 80’s (1987 to be exact, in Chicago and Vancouver) Starbucks started to expand outside Seattle. They offered something new and exciting – espresso drinks - and the mainstream North American espresso market was born.  Prior to this, espresso machines were mainly confined to the Italian district and farmers’ markets.

     

    What was not fully understood by these early coffee roasters and coffee entrepreneurs (including Starbucks), was that espresso had completely different dynamics than the traditional pourover coffee methods which required a different blending paradigm. The Italians, with a long head start, had already concluded that Robusta improved the espresso shot.

     

    Robusta is a species of coffee plant (Coffea canephora) quite distinct from the more widely cultivated Arabica species (Coffea arabica). It makes up from 20 per cent to 30 per cent of the overall coffee market worldwide, with India, Sumatra and Uganda supplying some of the better wet-processed varieties.

     

    Figure 1: Arabica vs. Robusta Bean

    Figure 1: Arabica vs. Robusta Bean

     

    Like any food product, Robusta can range from very high-quality (sometimes scoring higher than similar quality Arabicas) to a wretched product with tasting descriptions like bitter, acrid and tarry. One ongoing problem, which needs to be resolved, is that 10 times the number of defects (substandard beans) are allowed in Robusta coffee lots, compared with Arabica. This makes it harder to select high quality Robusta with low defect counts.

     

    Of the 700 or so coffee roasters in Italy, you can be sure not all are using high quality Robusta. Ten per cent of green bean imports to Italy are from India, which has some very respectable Robusta. Discouragingly though, another 10 per cent is from Vietnam – known for particularly low quality Robusta. If anything but a very high quality Robusta bean is used, it will drag down the espresso with bitterness and unpleasant flavours, another reason for its so called “bad reputation” by roasters unfamiliar with Robusta.

     

    High quality Robusta, on the other hand, has some important redeeming qualities as an ingredient in espresso coffee. It produces quite a bit more crema, the sensory layer on top, which is crucial to a good espresso.


    The crema is sturdier and lasts longer, which helps hold the flavour in, and allows the customer to make it to his table with the layer of crema intact.

     

    Having a long lasting crema for the patron to enjoy has another major benefit: crema coats the tongue (the more the better) and in doing so, it seems to insulate the taste buds from the inherent bitterness that all espressos have to a degree. This brings a more pleasing taste.

     

    Since Robusta is naturally low in acidity, it helps balance out the acidity (brightness) of the Arabica beans – which is accentuated in the espresso brewing process. What is a benefit in drip (brightness/acidity) is, counterintuitively, a detriment in espresso.

     

    High quality Robusta also adds a complexity of taste that cannot be duplicated by a straight Arabica blend. Caramel, chocolate and toast notes are more often described in espresso made with some Robusta in the blend.

     

    Because of the past association of Robusta and cheap supermarket coffee, “100 per cent Arabica” was an advertising slogan that worked well for the specialty coffee industry. Robusta was an easy target (and a legitimate one), for the drip coffee market.  If one scratched below the surface though, a few highly regarded artisanal roasters (coincidentally, almost all with Italian roots), were adding quality Robustas to their espresso blends.

     

    A few of those pioneers continue to excel and lead in their market – in Seattle, David Schomer of Vivace Espresso,  Mauro Cipollo (since retired) of Café d’Arte and  Dr. Joseph John, of Josuma coffee, based in California. When talking to industry peers, they will openly talk about the benefits of Robusta in espresso, but to the end users— the customers— the word Robusta is never heard. In fact, while designing a new label for our own coffee, I was discouraged by a few industry friends from putting the word “Robusta” on the label! We put it on.

     

    Kenneth Davids, a 40-year coffee veteran, author of three coffee books, and co-founder of The Coffee Review,  is a proponent of 10 to 20 per cent quality Robusta in espresso blends. He says, when given a choice of four espresso blends, three with only Arabica and one with a Robusta blend, customers invariably pick the Robusta blend.

     

    Today, there are Robusta beans grown in India and Sumatra that are handled and processed better than a lot of washed Arabica coffees. Lest anyone think Robusta coffee is inferior to Arabica, Indian Sethuraman Estate is a three-time winner of “Best Robusta” in the Coffee Board of India’s Flavour of India competition and it received the highest-ever rating for a Robusta coffee of 94 points from the same Kenneth Davids (most Arabica’s score in the high 80s).

     

     

    Major Arabica and Robusta Producing Countries. Source: Sara Lee

    Figure 2: Major Arabica and Robusta Producing Countries. Source: Sara Lee

     

    Davids described the flavour as having a “Deep aroma: sweet nut, hints of orange, toast and vanilla. Smooth, buttery mouth-feel and pungent flavors of cedar, more orange and caramel, toasted grains and a hint of flowers.

     

    Dr. Joseph John, another industry veteran, writes: “Perhaps the most significant effect of premium Robusta is its ability to enhance the richness and longevity of crema without detracting from the neutral character that is so critical for a superior espresso. It also adds to the unique flavor profile—typical of European espresso— that I believe cannot be obtained with Arabica alone…. crema is the single most important indicator of well-made espresso, and it is essential for capturing the intense flavors of ground coffee.

     

    Robusta: Valid but not Mandatory


    Tom Owen of Sweet Maria’s (a leading online supplier of specialty coffee) says this about Robusta: “There is a core use for Robusta coffees that are picked, sorted, processed and prepared with as much care as top grade Arabicas; this valid use is in the 5 to 20 per cent range in espresso blends. Robustas add body, crema, and a distinct flavor to espresso. If you are familiar with traditional Italian espresso you will recognize this taste. It also aids the espresso in distinguishing itself in milk drinks.” In fairness, he is not insistent on Robusta use, he is also passionate about the unique taste profiles of his all-Arabica espresso blends.

     

    One of the fathers of modern espresso in Italy, Dr. Ernesto Illy, also believes in only using 100 per cent Arabica in his espresso blends. But Illy is probably one of the finest blending and roasting companies in the world. They concentrate exclusively on espresso, have been doing so for over 75 years, buy exclusively from the source (the farm), and train those same coffee farmers on improving their coffee crops.  It is possible to make a good 100 per cent Arabica espresso blend – it just requires great sourcing skills and experience to do it properly; a skill that can take generations to fully develop.

     

    Espresso brewing places high demands on the beans chosen. Espresso will accentuate both the positives and negatives of a bean. So roasters in North America may not have the confidence to use it, or just don’t have access to the highest quality beans at source. Choosing and blending the right amount of Robusta for espresso might be the toughest job in the coffee food chain.

     

    Using a judicious amount of Robusta enhances espresso—it adds thick, long lasting crema, provides a smooth, more rounded taste usually with caramel and chocolate notes.  It lowers acidity and leaves a more pleasing aftertaste.

     

    You would think, with those epicurean qualities, we in North America would be enjoying it like the Italians– with great enthusiasm, frequently, and with not  more than a tablespoon of milk added, at most, an espresso macchiato (6 oz. cappuccinos are acceptable as part of the breakfast routine!). The Italians drink something like 3 million espressos per hour! Does anyone think for a moment, that they would collectively punish themselves with a drink they didn’t find enjoyable? The reality in North America is not so encouraging.

     

    After 25 years of exposure, almost no one consumes straight espresso in commercial establishments.


    This, in spite of the fact that baristas are often elevated to the same status as rock stars. We have local, regional and national Barista competitions, culminating in the World Barista Championship. We have numerous trade shows, dedicated magazines and multiple levels of barista training. The whole espresso industry has built an aura of “specialty gourmet” surrounding it. Some third wave coffee bars seem to have the same self-importance as upscale wine bars.

     

    And yet, in North America, less than 5 per cent of total espresso machine drinks are served as espresso! Why? Simple, the vast majority of customers taste an espresso once and aren’t impressed. It becomes their first and last. Some of the over the top descriptions of espresso don’t live up to the experience in the little cup either. The vast majority of espresso is only palatable when diluted with plenty of milk (or water as in an Americano).

     

     

    Figure 3: Arabica and Robusta producing countries. Source: Sara Lee

    Figure 3: Arabica and Robusta producing countries. Source: Sara Lee

     

     

    A post on the Homebarista website summed it up nicely (if not bluntly):

     

    “In Italy 90 per cent of the espresso is drinkable and 10 per cent is crap; outside Italy 90 per cent of the espresso is crap; 9 per cent is drinkable and 1 per cent is brilliant.”


    In other words, in North America, the unwary customer has about a 10 per cent chance of getting a passable, drinkable  espresso.

     

    Imagine if a new North American distillery operated the same way.  They have discovered (they think) a better method than the Scots to make great single malt whiskey. Sales seem to be good.  They conduct a marketing survey and find less than 5 per cent of their customers actually drink it neat (the way they intended). The other 95 per cent only find it palatable when mixed with generous amounts of ginger ale, soda or coca cola!

     

    It’s fine to interpret a product, but if it’s not an improvement in the customer’s acceptance of it, is that progress? If we can recognize that the Italians have refined a great recipe and have the customers to back it up, then let’s honour that tradition.

     

    If you want to provide your own twist on a standard, as an artist and an innovator, I can applaud that. But let the customer know that it’s not an Italian espresso you’re about to serve – it’s an American-style espresso. If I, as a customer, know this in advance, I can make an informed decision on whether I want it.

     

    The CoffeeResearch website says this about espresso: “The best espresso should be extraordinarily sweet, have a potent aroma, and flavor similar to freshly ground coffee. The crema should be dark reddish-brown and smooth, yet thick. A perfect espresso should be enjoyable straight with no additives, yet bold enough to not disappear in milk. A pleasant and aromatic aftertaste should linger on the palate for several minutes after consumption.

     

    So to the question: Robusta: Friend or Foe? I say friend, in espresso. And if the espresso I just finished doesn’t bring a satisfying smile to my face 90 per cent of the time, I also say, maybe it’s time to re-think the recipe!

     

    References

     

    1. http://www.sweetmarias.com/coffee.other.robusta.php
    2. http://kaapiroyalecoffee.com/tag/ken-davids/ (2009)
    3. http://www.coffeeresearch.org/espresso/potential.htm
    4. USDA GAIN report No. IT047, 2010

     

    About the author, Reg James of Espressotec

    I have 25 years of experience in espresso; everything from roasting to retail. On top of having my Level 3 barista license, I’ve previously operated three successful espresso coffee shops in Vancouver, Richmond, and Banff. Currently, I am the owner and operator of Espressotec Sales & Service, selling and servicing both home and commercial machines for over 15 years.


    This post was posted in Uncategorized, Coffee and Espresso Facts, Espresso Equipment

  • The Dynamics of Espresso - Changing the Taste of Espresso in North America

    Posted on January 13, 2013 by vyee

     

    Changing the taste of Espresso in North America

     

    How flat and "humped" extraction temperatures affect the taste of espresso

     

    Espresso was invented, mastered and perfected in Italy. It is a daily ritual—an obsession even— if one is to believe the numbers.  Almost three million shots are poured on average every hour of every day!

     

    Strict standards apply. One must acknowledge that after 100 years of refinement, the Italians know their product well. The Italian National Espresso Institute has a 12-page rulebook for espresso! A total of 61 words is used to described the preferred shape and mass of the perfect espresso cup and every parameter is strictly controlled from a seven-gram dose, to a 67-degrees Celsius cup temperature, to a specific blend of beans.

     

    Because of this standardization in Italy, it’s possible to walk into virtually any location with an espresso machine and receive a professionally made espresso. The barista preparing it will likely have apprenticed for 10 years as a bar assistant prior to being entrusted with the top job of Barista. Taste variations, for the most part, will be from the roaster chosen, and the recipe is a closely guarded secret.  One divergence is that the further south you venture, the darker the roast becomes, and the smaller the drink.

     

    The overwhelming majority of espresso machines in Italy are heat exchanger (HX)-style machines. These, by their very design, produce a “humped profile” (temperature declining). If you believe the Italians, a temperature declining profile provides the most balanced and rounded espresso taste.  Conversely, many of the progressive baristas in North America believe that an absolute flat, stable temperature is best.

     

    Why this divergence of opinion? In North America more than 95 per cent of the drinks are largely milk-based drinks, which places heavy demands on the espresso machines. In turn, this causes considerable temperature fluctuations. In an effort to tame this instability, many North American baristas turned to double boiler machines, which at the time provided a more stable temperature, even though almost no one in Italy used them. In effect, we decided to change the recipe instructions.

     

    If the Italians have refined the equivalent of a classic recipe over the past 100 years, why were we changing it?

    No one calls into question the extremely strict recipe and rules for making Parmigiano-Reggiano (parmesan) cheese or tries to improve upon the taste of Campari and still call it Campari?

     

    Michael Teahan, a long time industry advocate, says that almost no one in Italy besides La Marzocco is interested in producing machines with perfectly flat brew temperature profiles. The Italians seem to prefer a slightly higher initial temperature at the start (the hump) followed by a slightly declining temperature profile— precisely what HX machines provide.

     

     

    Figure 1: Flat vs. Humped Profile

    Figure 1: Flat vs. Humped Profile

     

    A recent North American argument has been that tightening up starting temperature accuracy seemed to produce a better shot. Would not the logical extension of this theory be that a flat, constant temperature throughout the pour would be perfect? Maybe, if we were dealing with something other than a food product and cooking, but that is exactly what espresso is.

     

    We sauté onions to caramelize them; we also sear a steak.  Searing uses higher initial heat to caramelize the sugars that give us the flavour we want. Then we “profile” the heat down to finish the cooking to our preferred doneness.  Even the lowly slice of toast benefits from a profiled temperature. The best taste and texture comes from browning on the outside, with a warm and soft inside.

     

    Espresso blends, by their very nature seem to benefit from a humped temperature extraction.

     

    Many traditional roasters roast each bean variety separately, based on the optimum roast for that particular bean. A long-held rule for espresso extraction is: the darker the roast the less the brew temperature, and vice versa. So how can a single flat temperature profile possibly bring out the best of a bean?

     

    In espresso, using a temperature profile that starts off a little higher seems to boost sweetness and the caramel flavours that are otherwise more muted. This ramping down seems to particularly benefit espresso blends, where different beans may each have their own unique optimum temperature band.

     

    If the extraction is taking place over several degrees of temperature (for example from 204 to 199 degrees Fahrenheit) each degree of change draws out different flavours and gives a much more full and complex flavour than a flat profile. It seems to reduce the bitter and sour characteristics and allow the subtler notes to flourish and the caramel and sweetness to shine through.

     

     

    Figure 2: Customer temperature profiling available on the Rancilio Xcelsius

    Figure 2: Customer temperature profiling available on the Rancilio Xcelsius

     

    A humped profile also benefits another common theme these days in North America: using larger coffee doses. The larger the dose, the more the heat of the brewing water is absorbed, which favours a higher initial temperature hump.

     

    Recently, it has become fashionable in many of the (so-called) third wave coffee bars to experiment with single origin Arabica beans for espresso.  Aside from the higher acidity (not desirable in espresso), many of these are roasted lighter and are not well suited to the complexity of taste that espresso demands.

     

    In this case, a perfectly flat temperature profile may be more suited to single origin espresso, since only one bean is involved. Here, the barista may want to highlight the same flavour notes discovered in the cupping. But what makes a single origin a great drip, pourover, or French press coffee, is certainly no guarantee it will be a great espresso.

     

    Having a higher finishing temperature (as in a flat profile), means that the cut-off time is more critical and in fact, most all baristas using machines with flat profiles, have found that split-second timing of the shot is crucial. Having a lower temperature at the end of a pour (as in a humped profile) seems to allow a little more leeway of time. In the real world of making hundreds of drinks a day, this probably translates into less undesirable shots made.

     

    Now, it might seem logical to the casual observer that the simplest way to resolve this question would be to have a simple comparison test. Pick two machines, one a double boiler with a flat temperature profile, and the other a HX machine with a humped temperature profile, and have at it. Line up some judges or even let the customers decide!

     

    To my knowledge, this has never officially been done at any coffee trade show before (I have been attending for some 20 years!) As was pointed out to me, by a long time industry veteran, which machine manufacturer is going to agree to such a test with so much at stake?

     

    In September, 2012, at CoffeeFest in Seattle, the first ever, officially sanctioned espresso tasting competition (America’s Best Espresso Competition),  was held. Thirty-five roasters from 16 western states and provinces competed against a panel of judges, using their choice of any of four different commercial machines. And, unlike the World Barista Championship, chefs and non-professionals were used as judges, not industry insiders.

     

    The machines were: a Slayer with a PID-stabilized flat temperature profile; a Nuova Simonelli with PID and oversized grouphead for a stabilized, flat temperature profile, a Wega Green Line with dual boilers for flat brew temperature profile; and a Rancilio Class 9 Xcelsius machine with hybrid heat exchanger.

     

    For the first time ever, an espresso machine, the Rancilio Class 9 Xcelsius is able to produce any profile desired (up, down, flat). And with any desired starting and finish temperature, the barista has fast and predictable control to maximize the flavour potential for any blend of espresso.

     

    The results of the first ever espresso competition in America? Both 1st and 3rd place were made on the Rancilio Classe 9 Xcelsius.

    The profile was set to that which the Italians prefer— a down profile— almost perfectly emulating the humped profile!

     

     

    Figure 3: Basic Espresso Machine Heat Exchanger and Hydraulic circuitry (Source: Rancilio Group)

    Figure 3: Basic Espresso Machine Heat Exchanger and Hydraulic circuitry (Source: Rancilio Group)

     

    For some years now in North America, there has been an effort to redefine, the original Italian taste profile.  But in over 20 years of espresso experience in North America, espresso consumption has not moved upward; it has remained at about 5 per cent. There are a hundred reasons for this, but clearly, we have not been delivering a consistent, drinkable espresso.

     

    I think the Italian engineers and baristas have had it right all along. They still firmly believe that a humped, downward profiling extraction following strict preparation guidelines, produces the most consistent and full flavour from a professionally roasted espresso coffee blend.

     

    I think we can finally say, we now have the proof we need!

     

    References

     

    1. Coffee and Cuisine May 1998, The Science of Espresso: Engineered Mediocrity Part 1
    2. Espresso Machine Design, Michael Teahan (www.espressoresource.com)

     

    About the author, Reg James of Espressotec

     

    I have 25 years of experience in espresso; everything from roasting to retail. On top of having my Level 3 barista license, I’ve previously operated three successful espresso coffee shops in Vancouver, Richmond, and Banff. Currently, I am the owner and operator of Espressotec Sales & Service, selling and servicing both home and commercial machines for over 15 years.


    This post was posted in Uncategorized, Coffee and Espresso Facts, Espresso Equipment

  • The Dynamics of Espresso - Espresso Machine Design

    Posted on January 13, 2013 by vyee

    Espresso Machine Design: Brew Temperature Stability versus Repeatability

     

    The Myth of a Precise Brew Temperature

     

    The temperature of the hot water that passes through a “coffee puck” while brewing an espresso has a crucial influence on the final taste. A temperature between 195 degrees Fahrenheit and 205F is the generally accepted range, with every degree (or 1/10th of a degree, some will argue) producing a different taste profile.

     

    It has become fashionable by many (especially in North America) in the specialty espresso industry, to subscribe to the theory that a perfectly flat, stable, brewing (pour) temperature is the magic bullet for a perfect espresso. They believe that by engineering, or re-engineering, the espresso machine with PID (proportional, integral, and derivative) devices, double boilers or even oversized groupheads to achieve this perfect temperature stability, a perfectly balanced espresso will magically result.


    If this theory were true, then everything the overwhelming majority of Italian coffee engineers believe in, and have tried to perfect in the last 100 years, is wrong. The Italians don’t want the same temperature throughout the pour.

    What they do want is temperature consistency and repeatability from shot to shot.

     

    These two concepts are not the same, but are crucial to this discussion.

     

    Achieving a perfectly flat brew temperature is another science experiment, insofar as achieving the “Holy Grail” of a “perfect” espresso. It’s one more recipe, and not necessarily the best, for most espresso blends (discussed in the article “Changing the taste of espresso").

     

    So, how did all this flat profile theory start, anyway? Back in 1998, in Seattle, one of the great early advocates and pioneers of espresso, David Schomer, did some experimentation with boiler temperature and grouphead temperature. He was frustrated (and justifiably so) by the wide temperature swings of the brew water of his la Marzocco double boiler machine (up to 6F between shots) and decided to stabilize it (see  Figure 1).

     

     

    Figure 1: Temperature changes beyond anticipated machine design and usage

    Figure 1: Temperature changes beyond anticipated machine design and usage

     

    After some tinkering and modifications, he reduced the temperature swing to within about 2 degrees, then proclaimed this temperature stabilization improvement as the path to perfect espresso. The next goal: accuracy to 1/10th of 1 degree! All this based on one machine, one set of tests and one espresso blend. But his widely read industry articles carried weight (and the majority of his articles were, and still are, well thought out and insightful).

     

    He was correct on the one point: boiler water temperature management certainly needed improvement (remember, this was the mid 90’s). But it was a long stretch to draw the parallel conclusion that stabilizing the water temperature throughout the shot pour (a flat profile) was also a desirable goal.

     

    Michael Teahan, another long-time industry advocate, is the current VP at Espresso Resource in the USA (a leading supplier in the Espresso industry), and a former technical director with an Italian espresso machine manufacturer. In a technical presentation prepared for the SCAA (Specialty Coffee Association of America) several years ago, he had this to say:

     

    “There is an assumption that the holy grail of espresso machine manufacture is the ability to precisely maintain a specific temperature throughout the extraction process tailored to a chosen espresso blend. Notwithstanding that a blend of beans, by its very nature may require a plurality of extraction temperatures to achieve optimal results, the Italian engineers with whom I have worked take it for granted that a flat line temperature profile is NOT what they want.”

     


    The important factor is how to keep the brew water temperature stable (repeatable) between shots and throughout the day. Machine design plays a key role in temperature stability – different manufacturers take different approaches. How (and where) the machine is being used also plays a huge role. Italy and North America are vastly different markets.

     

    The repeatability of the temperature of the brew water at the moment of the start of a brew cycle is also very important. This is the temperature of the water hitting the packed coffee bed at the start of each brew cycle. In Figure 2, this is the start temperature. Notice it is exactly repeated each shot. This graph is an actual Rancilio R & D data log from a late model heat exchanger (HX) machine with advanced boiler management (ABM).

     

    Notice also that the temperature overshoots slightly, just after the ramp-up (to account for heat absorption in the coffee bed), and then starts a controlled drift downward. This is the classic humped profile and it is engineered this way on purpose.

     

    Today, most of the top brands of commercial machines have vastly superior water temperature stability when compared with the earlier mechanical machines. The temperature repeatability of these machines (electronic models are especially stable) are accurate enough that the barista need not worry about temperature swing anymore.


    PIDs: Right problem, Wrong answer

     

    Schomer was one of the first to experiment with a PID controller as early as 2000 to control temperature stability. He learned that controlling the water temperature at the grouphead made a difference, but could often be compromised by fluctuating water temperature in the boiler, travelling to, and through, the grouphead when at idle and during heavy use. His work with PIDs led him to become an early advocate of this system.

     

    Over time, much faith was put into PIDs’ ability to stabilize temperature. Just throw a PID onto a boiler and presto—instant temperature stabilization. If the display readout says it’s stable, it must be true.

     

    Or perhaps not, as Teahan wrote in 2006:

     

    “With PIDs, it is possible to maintain boiler temperatures to within a few tenths of a degree. So long as you don’t steam any milk, draw any water or make too many shots.”

     

    This is because PIDs work best within a very narrow range— essentially they will keep an idle machine temperature stable.

     

    Teahan further explains: “While the program necessary to maintain temperature is very precise, it is not the same program necessary to respond to rapid changes in boiler temperature that occur when steaming milk or when the boiler refills with fresh water. By the time that the PID controller has sensed a dramatic change in temperature enough to call for full power to the heating element, it may have already dropped below the temperature at which a pressure stat would have come in at full power, as much as 6F. The program necessary to accurately recover from such a drop is also different from that required to maintain temperature and the controller may overshoot the set point slightly, or be too cautious (depending upon the program) and stabilize too slowly.”

     

    Baristas think a PID display is showing the brew water temperature at the point of extraction (just above the coffee bed). This is not true. It is reading the higher temperature back in the boiler, then working backwards to give a theoretically calculated brewing temperature at the grouphead. This is called the offset temperature and is an average number determined by engineers in the lab, but has no real-world application.

     

    Other factors in the coffee bar environment, such as ambient air temperature which can vary considerably in a coffee shop for example, will cause the actual grouphead temperature to fluctuate from the display reading. All the while, the PID display is showing a perfect set temperature because it’s reading the protected boiler water. In Teahan’s own words, “the number is a fairy tale.”

     

    Exposed groupheads, seen these days on machines in some trendy coffee bars, while looking impressive, are susceptible to air temperature changes. They can be affected by everything from wind chill on an outdoor cart, to air conditioning in a mall. Some PIDs allow for offset adjustment to compensate for local conditions and variations. Is this advancement, or more compensation for the machine’s limitations? Variables that are introduced to all but the most highly trained baristas are very often counterproductive. So rather than the desired flat profile, the systems deliver a random temperature profile.

     

    Competition is fierce within the specialized world of espresso machine manufacturers.

     

    Teahan says: “Espresso machine manufacturers spend hundreds of thousands of dollars each year, developing new products and refining old processes. Secretive offices manned by engineers with degrees spend countless hours over the course of many years working out the details of a particular group design or heat exchanger configuration.

     

    As an example, here is a partial list from one manufacturer, Rancilio, and their technical improvements in just the last decade (full disclosure – I sell Rancilio machines). Boiler power has been increased on all their performance 2 group and larger machines to 6,000 watts. This provides near instantaneous boiler reheat. Boiler water temperature is read by a sensitive (1-degree Celsius) pressure transducer which provides instantaneous element power when needed, which avoids the lag or overshoot of PID systems. They have developed computer technology (ABM), which reacts instantly to the big enemy of stable boiler temperature: auto-boiler fill (adding cold water to the boiler). A grouphead redesign now includes a larger pre-infusion chamber, which in turn is fed by a calibrated gigleur jet to provide dampened water flow to the coffee bed.

     

    All these innovations are meant to

     

    • 1. improve brew temperature stability and repeatability,
    • 2. provide the barista with a reliable machine that is entirely predictable,
    • 3. allow the barista to concentrate on serving a highly repeatable beverage.

     

    What has not changed is the signature humped temperature profile provided by the heat exchanger system. That curve provides a unique taste profile unique to each manufacturer. An espresso blend often consists of up to five different beans, all roasted to a slightly different level. A single temperature cannot possibly capture all the nuances of each bean.

     

     

    Figure 2: Data logged R&D measurements of a Rancilio heat exchanger (HX) machine with standard ABM (advanced boiler management)

    Figure 2: Data logged R&D measurements of a Rancilio heat exchanger (HX) machine with standard ABM (advanced boiler management)

     

    As was stated by Sergio Michael of Illy Caffe at the SCAA convention many years back, each water temperature gives you a different espresso profile.

     

    A plurality of extraction temperature produces more high and low notes, more sweetness (caramel), more chocolate notes (depending on the blend) and generally, a more well-rounded espresso.

     

    North America's Obsession with Flat Brew Temperature

     

    By their very nature, espresso blends, seem to benefit from a humped temperature extraction.

     

    Firstly, coffee bean screening allows for some size variation. Each bean roasts slightly differently and therefore will also extract slightly differently. Different varietals in the blend also extract slightly differently. For example, Robusta extracts slightly differently than Arabica. Even the processing of the coffee cherry—washed, semi-washed and dry— can affect the properties of the roasted bean. This can be seen in daily practice. Every time a new blend or even a new roast is run through the espresso grinder, the grind must be dialed-in again to achieve the proper pour characteristics through the espresso machine.

     

    So in the real world of day-to-day espresso shot pulling, the barista has a couple of choices: work with a machine with constantly moving temperature targets, and often missing the mark, or, work with a machine that brews with the plurality of temperature and catching a high percentage of the developed flavour notes.

     

    Old School, New School

     

    The vast majority of espresso machines sold in the world, whether lever, hydraulic, or any version of heat exchanger semi-automatic and fully automatic machines (including superautomatics), by the very nature of their design, produce a humped extraction temperature.

     

    A trip to Italy will find a wonderful variety of machines of every vintage and style. In Naples, arguably the centre of the espresso universe, 90 per cent of the machines in use are old school 3 and 4 group lever machines! So, what’s this obsession in North America with 1/10th of a degree flat brew temperature?

     

    To try to out think the Italian engineers who have spent decades perfecting their craft, by insisting on a ruler-flat temperature profile, we are distancing ourselves from the original Italian taste profile: a smooth, complex, sweet, and eminently drinkable espresso.

     

    In Italy, at least, the customers agree with what is being served, to the tune of almost 70 million espressos a day.

     

    And here in North America, we are trying, but not always getting it right.

     

    References

     

    1. Coffee and Cuisine May 1998, The Science of Espresso: Engineered Mediocrity Part 1
    2. Espresso Machine Design, Michael Teahan (www.espressoresource.com)

     

    About the author, Reg James of Espressotec


    My coffee enlightenment began when I discovered Timothy’s Coffees of the World in the (then) new Eaton Centre in Toronto in 1977. On my travels, I would take precious bags of fresh roasted beans (Costa Rica Tarrazu, one of my favourites) back to Yellowknife, NWT, and savour the brew during many a dark and cold winter day.

    In 1987— the year Starbucks opened its very first store outside of the US— at Vancouver’s seabus terminal, I began my coffee career. I started off by rebuilding a vintage 1930 Probat coffee roaster obtained from one of the original fathers of artisan coffee, Jim Stewart, then of Stewart Brothers Coffee in Pike Place Market, Seattle (later to became Seattle’s Best Coffee).

    I then went on to operate three successful espresso coffee shops in Vancouver, Richmond, and Banff. The store was recommended in “Vancouver’s Best Spots” book in 1997 (for custom roasting, varietal coffee-to-order for our customers). I also have my Level 3 Barista certificate.

    Presently, I am the owner of Espressotec Sales & Service, selling and servicing both home and commercial machines for over 15 years.

     

     

     


    This post was posted in Uncategorized, Buying Guides, Coffee and Espresso Facts, Espresso Equipment

  • The Case for Drinking as Much Coffee as You Like

    Posted on December 24, 2012 by espressotec

     

    Originally from the Atlantic by Lindsay Abrams on Nov 30th, 2012

     

    "What I tell patients is, if you like coffee, go ahead and drink as much as you want and can," says Dr. Peter Martin, director of the Institute for Coffee Studies at Vanderbilt University. He's even developed a metric for monitoring your dosage: If you are having trouble sleeping, cut back on your last cup of the day. From there, he says, "If you drink that much, it's not going to do you any harm, and it might actually help you. A lot."

     

    Officially, the American Medical Association recommends conservatively that "moderate tea or coffee drinking likely has no negative effect on health, as long as you live an otherwise healthy lifestyle." That is a lackluster endorsement in light of so much recent glowing research. Not only have most of coffee's purported ill effects been disproven -- the most recent review fails to link it the development of hypertension -- but we have so, so much information about its benefits. We believe they extend from preventing Alzheimer's disease to protecting the liver. What we know goes beyond small-scale studies or limited observations. The past couple of years have seen findings, that, taken together, suggest that we should embrace coffee for reasons beyond the benefits of caffeine, and that we might go so far as to consider it a nutrient.

     

    ***

     

    The most recent findings that support coffee as a panacea will make their premiere this December in the American Journal of Clinical Nutrition. Coffee, researchers found, appears to reduce the risk of type 2 diabetes.

     

    "There have been many metabolic studies that have shown that caffeine, in the short term, increases your blood glucose levels and increases insulin resistance," Shilpa Bhupathiraju, a research fellow at the Harvard School of Public Health's Department of Nutrition and the study's lead author, told me. But "those findings really didn't translate into an increased risk for diabetes long-term." During the over 20 years of follow-up, and controlling for all major lifestyle and dietary risk factors, coffee consumption, regardless of caffeine content, was associated with an 8 percent decrease in the risk of type 2 diabetes in women. In men, the reduction was 4 percent for regular coffee and 7 percent for decaf.

     

    The findings were arrived at rigorously, relying on data from the Nurses' Health Study and the Health Professionals Follow-Up Study, two prospective studies that followed almost 80,000 women and over 40,000 men from the 1980s through 2008. Although self-reported, the data is believed to be extremely reliable because it comes from individuals who know more about health and disease than the average American (the downside, of course, is that results won't always apply to the general population -- but in this case, Bhupathuraju explained that there's no reason to believe that the biological effects seen in health professionals wouldn't be seen in everyone else).

     

    That there were no major differences in risk reduction between regular and decaf coffee suggests there's something in it, aside from its caffeine content, that could be contributing to these observed benefits. It also demonstrates that caffeine was in no way mitigating coffee's therapeutic effects. Of course, what we choose to add to coffee can just as easily negate the benefits -- various sugar-sweetened beverages were all significantly associated with an increased risk of diabetes. A learned taste for cream and sugar (made all the more enticing when they're designed to smell like seasonal celebrations) is likely one of the reasons why we associate coffee more with decadence than prudence.

     

    ***

     

    "Coffee and caffeine have been inexorably intertwined in our thinking, but truth is coffee contains a whole lot of other stuff with biological benefits," said Martin. And most concerns about caffeine's negative effects on the heart have been dispelled. In June, a meta-analysis of ten years of research went so far as to find an inverse association between habitual, moderate consumption and risk of heart failure. The association peaked at four cups per day, and coffee didn't stop being beneficial until subjects had increased their daily consumption to beyond ten cups.

     

    Caffeine might also function as a pain reliever. A study from September suggested as much when its authors stumbled across caffeinated coffee as a possible confounding variable in its study of the back, neck, and shoulder pains plaguing office drones: Those who reported drinking coffee before the experiment experienced less intense pain.

     

    The data is even more intriguing -- and more convincing -- for caffeine's effects as a salve against more existential pains. While a small study this month found that concentrated amounts of caffeine can increase positivity in the moment, last September the nurses' cohort demonstrated a neat reduction in depression rates among women that became stronger with increased consumption of caffeinated coffee.

     

    But that caffeine is only mechanism behind coffee's health effects is supported by a small study of 554 Japanese adults from October that looked at coffee and green tea drinking habits in relation to the bundle of risk factors for coronary artery disease, stroke, and type 2 diabetes known together as metabolic syndrome. Only coffee -- not tea -- was associated with reduced risk, mostly because of dramatic reductions observed in serum triglyceride levels.

     

    So aside from caffeine, just what are you getting in a cup, or two, or six? Thousands of mostly understudied chemicals that contribute to flavor and aroma, including plant phenols, chlorogenic acids, and quinides, all of which function as antioxidants. Diterpenoids in unfiltered coffee may raise good cholesterol and lower bad cholesterol. And, okay, there's also ash which, to be fair, is no more healthful than you would think -- though it certainly isn't bad for you.

     

    ***

     

    Some of the chemicals in coffee are known carcinogens, though as far as we know that's only been seen in rodents, not in the small levels we encounter in everyday consumption. Findings, on the other hand, have been supporting that coffee can protect against some cancers. When the Harvard School of Public Health visited the Health Professionals Follow-Up cohort in May 2011, it found that coffee's protective effects extend only to some types of prostate cancer (the most aggressive types, actually). In a separate study of the same population from this past July, they also found a reduced risk of basal cell carcinoma with increased caffeine intake.

     

    The association was strongest for those who drank six or more cups per day.

     

    That same high dosage is also effective in fighting against colorectal cancer, according to a prospective study from June of almost 500,000 adults conducted by the American Society for Nutrition. While the association was greatest for caffeinated varieties, decaf made a small but significant showing. A meta-analysis of 16 independent studies this past January added endometrial cancer to the group of cancers whose relative risk decreases with increased "dosage" of coffee. And in 2011, a large population of post-menopausal women in Sweden saw a "modest" reduction in breast cancer risk with immoderate consumption of 5 or more daily cups.

     

    Taking the benefits of coffee any further requires being patient-specific, but findings apply to a broad range of populations and conditions:

     

    If you have fatty liver disease, a study from last December found that unspecified amounts can reduce your risk of fibrosis.

     

    If you're on a road trip, you may respond like the 24 volunteers for an experiment from February who were subjected to two hours of simulated "monotonous highway driving," given a short break, then sent back out for two more hours. Those given a cup of coffee during the break weaved less, and showed reductions in driving speed, mental effort, and subjective sleepiness. If you're on a weight-training regimen, it can provide a mild (and legal) doping effect.

     

    If you're trying to enhance your workout, the results of one experiment from October found that drinks containing caffeine enhances performance. And then another one from Dr. Martin in 2008: He coauthored a study of people enrolled in Alcoholics Anonymous in which there appeared to be an association between upping coffee intake and staying sober.

     

    Nothing can be all good, and there is still information working against coffee -- in October, The Atlantic reported on a study from the health professionals cohort that suggested a link between excessive coffee consumption and glaucoma. "The current recommendation is that if somebody's not drinking coffee, you don't tell them to start," said Bhupathiraju.

     

    But she agrees that drinking coffee, and more of it, does appear to be beneficial. The evidence remains overwhelmingly in coffee's favor. Yes, it was observational, but the study published in May in the New England Journal of Medicine looked at hundreds of thousands of men and women and found this bottom line result: people who drank coffee lived longer than those who didn't.

     

    And the more they drank, the longer they lived. If you're into that sort of thing.

     

    View the original article in full screen by clicking here


    This post was posted in Coffee and Espresso Facts

  • Robusta Rehab by Richard Reynolds

    Posted on August 24, 2012 by espressotec

     

      It was hard to miss the “100% Arabica” sign at the Molinari Caffè booth during the Specialty Coffee Association of America’s (SCAA) conference in Seattle. But when asked about his all-arabica blend, Fabrizio Mengoli, Molinari’s export manager, shrugged his shoulders. “We have more than 100 years in coffee,” he said, “and we started to offer 100 percent arabica just this year because of the pressure. Our experience and philosophy is to mix between arabica and robusta. But we are in the market, and people asked to have 100 percent arabica, so we decided to play the game. ”Robusta has traditionally been used in Italian espresso blends, though that is changing, especially because of Ernesto Illy’s strong stance against its use. But many European roasters show little of the anti-robusta passion expressed by their American counterparts. No one will ever accuse coffee people of lacking opinions, but there are few subjects that will turn up an American roaster’s pressurestat more quickly than the mention of robusta.


    Continue Reading

    This post was posted in Coffee Roasting

  • Blending for Italian Espresso Part 2

    Posted on August 20, 2012 by espressotec






    View the article in full screen by clicking the link below:

    Blending for Italian Espresso: Part 2


    This post was posted in Coffee Roasting

  • Blending for Italian Espresso Part 1

    Posted on August 20, 2012 by espressotec






    View the article in full screen by clicking the link below:

    Blending for Italian Espresso: Part 1


    This post was posted in Coffee Roasting

  • Rancilio Silvia - Beginners Guide - Steaming Operation

    Posted on April 18, 2012 by espressotec


    This post was posted in Beverage Preparation and Techniques

  • Baratza Grinders Overview

    Posted on March 2, 2012 by espressotec


    This post was posted in Buying Guides

  • Aerobie Aeropress - How it Works

    Posted on February 1, 2012 by espressotec


    This post was posted in Beverage Preparation and Techniques

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