The cutting mechanism in a coffee grinder. Burrs are usually made from cast or machined metal, and ideally are sharp to the touch (they can easily cut skin when new). Burrs cut, rather than crush, your coffee beans and are more precise than a blade grinder (which does the opposite – it bashes the beans, does not cut them). Burrs are mounted so that one burr is fixed/stationary, and the other rotates using a motor or hand power. Some burrs are made from other materials, like reinforced ceramics. Ceramic burrs hold their edges longer than steel, but are also more brittle, and some ceramic burrs are cheaply made and have poor cutting surfaces.
Flat vs. Conical
This refers to the shape of the burrs and their cutting surfaces.
Conical burrs are named mainly for the inner burr, which is distinctly cone shaped. The outer burr usually looks like a thick ring, with a cone-shaped cavity inside it. Typically, the ring burr will be stationary, except in the case of the Baratza Sette, whose cone burr is fixed in place instead. Coffee moves through conical burrs from top to bottom – the tip of the cone will have the larger primary cutting faces, and the base of the cone will have the small finishing cutting faces. As such, conical burrs are essentially required to be mounted vertically so they may be gravity fed and their exit path will not clog.
Flat burrs are shaped like flattened donuts, and they are mounted parallel to each other with the cutting edges facing each other. Coffee enters through the central hole of one burr, is pushed between the burrs and through the cutting surfaces, and exits at the outer circumference of the burrs. Flat burrs can be mounted in a variety of ways – horizontally and parallel to the counter, at an angle, or vertically.
Sometimes you’ll find that people insist there are intrinsic benefits to conical or flat burrs, or that there are very distinct taste differences. Conical and flat burrs do have some different properties – conical burrs, for example, require less torque to grind and thus can use less expensive and lower powered motors, which is why they’re often found in lower end grinders. We can’t find much evidence to say that conical burrs always taste like X and flat burrs always taste like Y, and now that we’re learning more about the effect of burrs and grinder construction on grind uniformity, as the resulting effects on flavor, it seems like it’s harder to pin down whether flavor changes are due to burr shape or to the grind uniformity a specific grinder is producing.
Stepped Grind Adjustment
Stepped grinding refers to the means of adjusting the distance between the burrs, and thus the overall particle size of the ground coffee. Stepped grinders have discrete and finite settings (e.g. 0-40 or Fine-Medium-Coarse), and no in-between settings. There are some stepped grinders with so many settings that they may as well be stepless, as the gaps between settings are very small (like the Baratza Vario and Forte).
Stepless Grind Adjustment
As above, this refers to the means of adjusting the distance between the burrs and the resulting size of the coffee particles produced. Stepless grinders feature "infinite" grinding adjustment, with a smooth adjustment between all settings and theoretically as many in-between settings as you need. Often stepless grinders use a screw-style mechanism for adjustment, and sometimes incorporate a worm gear drive to make more precise changes. Mazzer grinders are stepless, with a thick, heavy screw collar for adjusting the grind. Anfim’s SCODY and CODY grinders are also stepless and also use a screw collar, but make adjustments with a knob on a worm gear for small and precise changes.
This term means different things to different people, but in the most general sense it refers to the leftover coffee grounds which remain stuck in the grinder after grinding. That is, if you start with a perfectly clean and empty grinder and grind a 30 gram dose, retention is how much coffee gets left behind, the delta between the input mass and the output mass. Coffee grounds will get lodged into the crevices of a grinder and the grinding path from the burrs to the exit chute, and less retention is always considered to be better. Retention is exacerbated when grinding very fine, as coffee has a tendency to stick to itself and clump, so espresso grinders generally have the highest retention.
In some cases, the word "retention" is used to describe all coffee in a grinder which is no longer in its whole bean state. A grinder with a hopper full of beans may finish grinding a dose, and there will be residual grounds left in the crevices and exit path as before, as well as grounds retained within the burrs and partially broken beans just inside the burr openings. These grounds and partials have more exposed surface area for oxygen to affect their flavor, and thus may be considered to be waste or undesirable if left for a long enough time. This definition of retention usually includes much more coffee than the above, so the two usages may be confusing if not specifically defined in context.
The overall effective range of grind sizes which a grinder can produce. Sometimes this is expressed vaguely, e.g. fine to coarse, or it may be expressed in terms of coffee brewing styles, e.g. Turkish, Espresso, Drip, Percolator, French Press. Expressing a grind range in an objective scale such as microns is still rare because it requires expensive equipment, and coffee doesn’t grind neatly into just one size (see Uniformity).
Relatively few grinders perform well across a full grind range from Turkish coffee fine to very coarse, and most operate best within a small window of grind ranges. Espresso grinders tend to be designed around producing a good quality grind at the fine end of the spectrum, and adjusting to a very coarse range may not only be tedious, the grind adjustment mechanism may not even be capable of doing so. Some commercial grinders, like the EK43, can execute well over a full grind range, but require calibration to reach either end of the spectrum. If the EK43 is calibrated for espresso grinding at a 2 on its adjustment dial, then a 20 (the coarsest setting on the dial) will not be a coarse enough grind for french press. The grinder may be calibrated by shifting its entire accessible range more coarse, but it will lose access to espresso grinding in the process.
Uniformity refers to how similarly sized the ground coffee particles are. Grind uniformity is a rather new field of exploration and it’s not entirely clear whether more uniformity is more desirable in all cases. This is seen as an important area of study stemming mainly from the trend of using large flat burr grinders for espresso and coffee brewing, as they seem to offer better flavor clarity, more sweetness, and less off-flavors when extracted more vs other more traditional grinders. Laser particle analysis (LPA) has been used to show that large flat burr grinders often yield a more unimodal (i.e. more uniform) grind size distribution.
Espresso is both the name of the machine and brewing style, as well as the name of the beverage produced. Espresso is brewed by forcing hot water under high pressure (usually around 9 bars/130 psi) through very finely ground coffee. The brew time is often quite short, around 20-30 seconds, and the beverage volume is typically a "shot" size of around 1-2 fl oz or 30-60 mL. Due to its high brewing ratio (coffee mass : beverage mass), espresso is a very strong beverage with intense flavor. It is also heavily influenced by slight changes in production technique, so factors like grind size, dose mass, beverage mass, brewing temperature, and so on can seemingly be amplified in the cup. The process of tweaking an espresso recipe to control for all the brewing factors and achieve a desired result is called "Dialing In."
Group Head – The interface of the machine where hot water is added to the coffee under pressure. The group head features a locking mechanism for the portafilter, a gasket material to create a seal against the basket rim, and a dispersion/shower screen to distribute the water evenly across the coffee. Group head designs will vary, though some designs are historically notable.
E-61 Group – Created by Faema in 1961, this is what’s known as a thermosyphon group. It is heated passively from the machine’s steam boiler, and maintains a somewhat steady temperature thanks to its large exposed surface area. It’s usually made in chromed brass, and features a mechanical three-way actuation – the down lever position opens the flush valve and shuts off the pump, the middle lever position opens the brew path and allows for line-pressure pre-infusion if available, and the up position engages the pump. E-61 groups are primarily found in heat exchanger style machines, but may be used in other applications as well.
Saturated Group – Popularized mainly by La Marzocco, but heavily adopted today. Saturated groups feature a chamber above the actual group interface which is full of hot water and usually directly connected to the brew boiler. This helps to maintain thermal stability during use and limits heat loss of the brewing water on the brew path between the boiler and the coffee.
Actively Heated Group – Rather than relying on brew water to heat the group, some newer machines actually actively heat the group with its own dedicated heating element. This element may heat a chamber of water, similar to the saturated group design, or it may heat the metal parts of the group directly. Actively heated groups can be found on Nuova Simonelli T3 machines, as well as the Sanremo Opera, and almost always include a digital temperature controller (PID) interface for the user.
Portafilters & Baskets
Portafilter – Usually refers to both the handle apparatus and the filter basket inside of it. This is the device which holds the filter basket, where coffee is packed in and held during brewing. Portafilters are usually heavy and sturdy, and made of metal like brass or steel. They may have a single or double spout, or they may be "bottomless," exposing the bottom of the filter basket. Portafilters come in a few different sizes, as there is no standard size, and different brands may have slightly different designs that make them incompatible with other machines.
Filter basket – Espresso machines require coffee to be packed into a filter basket, which is usually an open-topped steel cylinder with an array of holes punched into the bottom. Filter baskets come in a variety of sizes, both in diameter (58 mm is very common for commercial use) and in depth. The depth of a basket has a lot to do with the intended use and dose size, so a single shot basket will be shorter than a double or triple shot basket. Some baskets have a fairly specific dose in mind, such as VST brand baskets which are intended for doses of 15 grams, 18 grams, 20 grams, etc.
Ridged vs Ridgeless Baskets – Some baskets are formed with a slight ridge in the basket wall just below the top rim. This is intended to catch a corresponding wire spring inside the portafilter, which will hold the basket firmly in place so it does not fall out or become dislodged when knocking out a puck, wiping the basket, during storage, etc. Ridgeless baskets have no such ridge, and are straight-walled from top to bottom. They may fall out easily, or become dislodged, but the slight advantage is that ridgeless baskets are generally more precisely made with tighter manufacturing tolerances.
Preparation & TampingShop Tampers
Ideal Dose – Every basket has a theoretical ideal dose size, which fills the basket adequately enough for the coffee to swell and fill all the void space when hot water is introduced, so as to promote even flow through the puck. An under-filled basket may cause the coffee to expand unevenly, to become overly disturbed by the water flow, and cause extraction problems. An overfilled basket may impact the dispersion screen, fail to lock in properly, cause leaks, slow flow, and so on.
Distribution – Refers to the untamped grounds in the basket and how evenly they are spread as well as how evenly dense they are. Tamping an uneven bed of coffee will not resolve poor distribution, so focusing on good distribution practices is important to achieving good and consistent espresso extractions. There are many methods for coffee distribution, and a few tools which are purposefully designed for the task. One such method is the Weiss Distribution Technique, which involves stirring the ground in the basket with a thin probe, such as an unbent paperclip or a cake tester. Lynn Weber makes a tool called the Blind Shaker which also assists in distribution by shaking the grounds within a container before dropping them into your basket. Others have resorted to tapping the side of the portafilter with their palm to try to settle and distribute the grounds, or to using a jam funnel inserted into the basket to swirl the grounds around to more evenly push them around the basket. Note: it is important to distinguish Distribution, which focuses on evening the entire puck of coffee, and Grooming (below), which focuses mainly on the upper half of the puck.
Grooming – A type of distribution which mainly focuses on the topmost layer of grounds. Grooming is performed for a multitude of reasons: some grinders deliver an even and fluffy mound of coffee with good evenness in the basket, and the coffee only needs a light touch to distribute the uppermost surface before tamping; sometimes grooming is performed after distribution by tapping, again to settle only the topmost layer of coffee; sometimes grooming is done purely for aesthetic reasons, to make the coffee appear more neat and tidy before tamping. Grooming may be done with a simple tool like a spoon, a finger, or with a dedicated tool such as the Pullman Chisel.
Tamper – A device used to compact the ground coffee into the basket, usually small and handheld. The tamper base or piston is most often a piece of metal, usually steel, and ideally is sized to fit the basket somewhat snugly. Tamper bases are usually flat-faced, but sometimes come in other varieties, such as convex, or with a rippled design carved into the metal. There’s not a lot of evidence to say that anything other than a flat face is necessary, but alternative designs are also not necessarily detrimental.
Tamping – Tamping is the act of compacting the coffee grounds within the filter basket, to remove the air, create an evenly dense coffee puck, and prepare the coffee for extraction. Forgoing tamping is usually detrimental, as the air voids in the coffee puck lead to uneven and poor extraction – however sometimes the act of locking the portafilter in will tamp the coffee against the dispersion screen, provided there is enough coffee in the basket to reach the screen.
Tamping Force/Tamping Pressure – The amount of downward force applied to the tamper to compact the coffee in the basket. There are many varying opinions on how much force should be applied and how much it matters. Often values between 15-30 pounds of force are offered as ideal, and sometimes it may be suggested that varying the amount of force used will have discernible effects on shot pulling. Our findings are that somewhere around 20 pounds will suffice, so long as the coffee bed is adequately compacted and all voids are removed. Using an electronic tamper, we found no notable difference in shots prepared using anything between 20 pounds and 60 pounds of tamping force.
Espresso machines have a long history stemming from the late 19th century, and as such have experienced vast changes in their construction and the technology which is incorporated into their design. Early espresso machines were powered only by steam pressure, but have since been designed around pistons or pumps supplying the brew pressure.
Manual espresso machines typically use a lever action to drive a piston and force a column or charge of hot water through the puck of ground coffee. These may be Direct Lever machines, where the user supplies all the necessary force themselves, or Spring-assisted Lever machines, where the user cocks the lever to compress a spring, which then supplies the brew pressure as it decompresses. Manual espresso machines are somewhat unique in that they allow the brew pressure to be modulated either directly or indirectly by the user, meaning that the espresso could be extracted higher or lower than 9 bars at any point in the brew process. This does allow for some interesting experimentation if the user is experienced, but also can be frustrating for the novice because they may be applying inconsistent pressure without realizing it.Shop Manual Espresso
Semi-automatic machines are some of the most common on the market today. They use a pump to extract the espresso, and the user must both engage and disengage the pump manually, usually by pushing a button on the machine. Semi-auto machines range from extremely low budget to mid-high end, and can incorporate a whole host of other features depending on price level. The main defining characteristic is that they do not have settings for controlling the volume of a shot or the time for the shot to run.Shop Semi-Auto Espresso
Automatic/fully-automatic machines include dosing or time controls as well as semi-automatic functionality. These machines will have extra buttons for single/double shots, and sometimes more, and the machine will stop the shot when the button’s programmed cycle is complete. On commercial Italian-made automatic machines for example, it’s not uncommon to have all of the following program buttons: single short, double short, single normal, double normal, single long, double long, and continuous flow (semi-auto). These program buttons can be customized to deliver a certain volume of water, run for a certain time, or run a certain amount of meter cycles. Volumetric machines will use a flow meter, which is a small water wheel with a magnetic sensor inside, to determine either the volume of water that has been pumped, or how many rotations of the meter have occurred. Some newer machines use scales instead, to more precisely determine how much beverage mass has been brewed.Shop Automatic Espresso
Superautomatic machines are the do-it-all devices that you can find in Starbucks stores, offices, some coffee shops, and so on. They use whole bean coffee, but they run the entire brew cycle without assistance from the user. A user may simply push a button for "cappuccino" and the machine will dose the beans, grind them, brew the espresso, and steam the milk, then run a quick cleaning cycle on itself so it’s ready for the next drink. Most superautomatics only have a modicum of customizability, so the user may only be able to tweak certain volumes used, maybe change the grind size of coffee and little else. Others have robust controls with precise weights and measures, grind size and brew temperature control; almost anything you’d want to adjust. In many cases, superautomatics are considered to be far more convenient but lower quality than a semi-automatic alternative, as the machine does not know how to adjust espresso the way a human user does, and thus won’t be able to react to flavor changes as quickly or easily. Further, build quality and reliability are often issues for these machines.
Other Machine Types
Steam-powered "espresso" machines do not often meet the conventional criteria for espresso brewing, namely the required pressure and beverage strength. Often these machines have large carafe included, and generally function more like an electric moka pot than an espresso machine. The coffee is more dilute than your typical espresso and takes a bit longer to brew, and overall tastes and functions more like moka pot coffee.
Non-lever manual machines – Other manual machines exist which do not use a lever group. We carry the Nomad espresso maker, which uses a sort of air pump to push hot water through the coffee. There are also other novel designs like the Espresso Forge, which is a direct-piston style machine where the user pushes a long piston in a tall brewing chamber, or the Rossa espresso maker which pushes a piston with a screw as the user turns a handle.
Nespresso – Nespresso is a proprietary coffee brewing system made by Nestle. Nespresso brewers are functionally very similar to inexpensive home espresso machines, and brew using a self-contained pod of coffee with a built-in filter rather than a portafilter and basket. Nespresso is not quite espresso is the usual sense, but rather more like frothed moka pot coffee in terms of taste and brew strength. These machines have a built in mechanism which froths the coffee after it is brewed by forcing the liquid under pressure through a small aeration nozzle. This gives the appearance of crema, though it is essentially just a coffee foam. Nespresso offers a wide variety of flavors and blends in their pods, but there are few ways to adapt the machines for fresh ground coffee or custom brews.
Espresso Boiler Types
An espresso machine is built around heating water for brewing, and they often use a boiler to do so. Boilers come in a variety of style when it comes to espresso, and each style has some advantages and disadvantages to consider.
Open boilers are rare today, but may still be found on some vintage lever espresso machines, or more modern versions of the same. An open boiler is just as it sounds – it is an open-topped vessel in which water is boiled, like a tall pot with its own heating element.
Closed boilers are ubiquitous today, and are completely sealed except for their various ports for water to come in and to exit, plus some safety vents if needed. Closed boilers are able to build and contain steam pressure, which is important for the function of many espresso machine designs, as well as for steaming milk.
Thermoblocks are not boilers, but are instead more like a series of channels carved into a block of metal. The channels are sealed from the outside, like a boiler, and run alongside some kind of heating element. As water flows through the channels, it is heated by the element, and should exit at the desired brewing temperature. Thermoblocks are inexpensive to make and are common with very-low budget espresso machines. They are very susceptible to clogging from scale buildup, as well as failure due to poor construction.
Single boiler/dual use (SBDU) machines contain a closed boiler which is used to heat water for both espresso brewing as well as steaming. It can only be used for one function at a time, so the user must work with the design to properly make their coffee and steam milk. These boilers often use two thermostats – one for a lower temperature for espresso making, another for a higher temperature to create plenty of pressurized steam. Brewing espresso while the boiler is still at steaming temperature would either ruin the shot or be extremely challenging to dial in, so usually the user must either brew the shot first and then steam milk, steam first and wait for the boiler to cool before brewing, or try to flush the hotter water out of the boiler by running the pump. This means that making milk drinks with a SBDU machine takes longer than with other machines and can be somewhat challenging to work with.
Heat exchanger (HX) machines also have only one boiler, but instead it is used only for steam. It is usually a larger boiler with a capacity of 1 liter or more, so it can provide a good deal of steam and plenty of heat. The heat exchanger is a coiled tube which intersects the upper part of the steam boiler, which connects the water line or reservoir to the group head. As water travels through the heat exchanger coil, it is heated by the steam in the boiler. The coil is generally long enough that water will be sufficiently heated as it travels from one end to the other, so these machines can usually keep up with back-to-back shots without the brew water temperature falling too low. The water can, however, be overheated if it sits idle in the coil for too long, so HX machine users often perform a cooling flush to remove the overly hot water prior to pulling shots. These machines can brew and steam at the same time, and are generally fairly robust, so they’re often considered to be higher end or "prosumer" machines for the home, and some commercial machines also incorporate the design.
Dual boiler (DB) machines feature two boilers, one dedicated to coffee brewing and one dedicated to steam. These are often the most expensive class of espresso machine because of the amount of materials and resources which go into their construction, but they are also some of the most technically advanced. Nearly all high end espresso machines for home or commercial use are dual boiler machines. DB machines also frequently incorporate PID controllers to set the water temperatures for both the brew and steam boilers, meaning the user can customize boiler temperatures independently to suit their needs. Some commercial machines have individual brew boilers per group head, and each brew boiler can be independently set to a different temperature. This adds a great deal of flexibility and precision to the machine. As above, thanks to the dedicated boilers for each task, DB machines can brew and steam at the same time without impacting performance.
Pumps fall into three main classes – vibratory, rotary, and gear. A vibratory pump is the least expensive option and is found in most home espresso machines. They take a few seconds to fully ramp up to pressure, but otherwise work just fine. A rotary pump is often seen as more desirable as it can have its rotation speed changed to increase or decrease the pressure (with water, flow rate is directly tied to pressure). This is not something you can easily change while brewing espresso, however. Gear pumps are somewhat more advanced and can have their flow rate adjusted electronically, meaning they can be changed during a shot if the machine allows it. Rotary and gear pumps often require the machine to be plumbed in so they are supplied with steady mains pressure in order to work properly.
A brewing style intended for evaluating multiple samples of coffee all at once. Cupping has a standard protocol which was developed for green coffee buyers to use while evaluating samples from lots, farms, mills, co-ops, etc., in as even-handed a way as possible so the coffees remain the only real variable. Cupping involves preparing 2-3 samples of each coffee in small glasses or bowls, evaluating the ground coffee aroma, adding hot water then evaluating the wet aroma, then allowing the coffee to steep, breaking the crust of coffee and evaluating the wet aroma again, then skimming the grounds off the cups and finally evaluating the samples by slurping the coffee out of a spoon. Slurping strongly allows the taster to spray their whole mouth almost simultaneously, which can improve taste perception. By sampling many coffees in rapid succession, a cupper can quickly evaluate the strengths and weaknesses of the coffees present. Cupping does require some skill to be done effectively, especially in a professional setting, but may be done casually to explore the differences between coffees. Cupping is also performed by roasters and retailers to evaluate samples, and may follow a customized cupping protocol to suit their individual needs.
A coffee maker invented by Alan Adler, the inventor of the Aerobie flying ring. Originally designed to produce just one cup of coffee in a short amount of time, the Aeropress has garnered a reputation for being a versatile and compact brewer, and thus far is one of the only coffee makers with its own dedicated worldwide competition circuit. The Aeropress isn’t quite like a french press, despite the name, and instead functions a bit more like a moka pot with a paper filter, using moderate pressure to force water through a small bed of coffee grounds. It can also be used inverted to allow longer steeping of the coffee, or used as a pour-over device with no plunging needed. While the creator used to claim the device makes espresso, due to the low brewing pressure and only somewhat stronger-than-normal brew strength, Aeropress coffee would be better related to moka pot coffee instead.
Automatic drip machines should be familiar to most coffee drinkers: they are brewers which spray or drip hot water over a bed of coffee grounds inside a cone-shaped filter basket, producing what most Americans know as coffee. Drip machines are quite common both commercially and domestically, with well-known brands like Bunn and Fetco, or Mr. Coffee and Bonavita. Auto drip machines in the home can have issues maintaining proper brewing temperature, mostly due to underpowered parts or oversimplified design. This is part of the reason that some would characterize drip coffee as sour or thin, though some of the blame certainly falls on the prevalence of brewing with and improper coffee ratio or grind size. In professional use, batch drip brewers can have robust control over temperature, water addition (e.g. control over pulse timing and water volume), and are capable of producing very excellent coffee in large quantities.
Pour-Over/Manual DripShop Pour-Over
Pour-over brewing is essentially just brewing drip coffee by hand. Where an automatic drip coffee maker sprays or sprinkles water somewhat evenly over a bed of ground coffee, a pour-over brew features the human brewer adding coffee with a kettle by hand. This can be more effective than some automatic coffee makers in that the human can be more exacting and precise than the machine, but it can also be less effective if the human pays less attention to the brew process or brewing factors like temperature. While some pour-over recipes may vary based on preferred technique and flavor results, they generally follow the same overall recipes and ratios as their automatic alternatives.
A device invented by Dr. Peter Schlumbohm in the 1930s, inspired by the laboratory glassware he knew so well as a chemist. The distinctive hourglass shape of the Chemex is derived from the shape of an Erlenmeyer flask and a glass filtration funnel put together. The Chemex is a pour-over style dripper with a built-in carafe, making it very convenient for both brewing and serving coffee. The device is intended to be used with proprietary bonded paper filters, which are quite thick compared to other coffee filter materials, and are again inspired by the laboratory materials he was so familiar with. While the brewer itself is somewhat unique, it’s really the filters that contribute the most to its characteristically clean and clear taste, so using a Chemex filter in another cone-style brewer will yield almost identical coffee.
V60Shop V60 Brewers
Hario’s signature cone-shaped drip brewer, named for the 60 degree angle of the cone’s profile. V60 drippers come in a variety of materials and sizes, all with the same cone angle. They are known for being somewhat unforgiving brewers thanks to the large hole opening at the base, which can be challenging to brew with without practice. The brew bed will drain very quickly, so most V60 recipes call for a finer grind than other drip cones and careful pouring technique to prevent over-dilution if water bypasses the brew bed and drains through without extracting much. Despite the reputation, V60 drippers aren’t impossible to work with and can be used to brew some very delightful coffees, with plenty of room to tweak recipes or brewing style to dial in each new coffee.
The Clever Coffee Dripper is an intriguing device as it combines immersion-style brewing as well as percolation when draining. It’s considered a steep-and-release brewer, where coffee and water are immersed for part of the brew, and then a plug is released from the bottom to allow the coffee to drain while being filtered by paper. As a result of this design, Clever Dripper recipes often have shorter brew times than pure immersion brewing, and incorporate a finer grind as well. The Clever Dripper can yield coffee with medium to heavy body, but clean flavors thanks to the paper filter.
Vacuum Pot/SiphonShop Siphon
The vacuum pot is a classic method of brewing, with history dating back into the late 18th century. Modern vacuum pots have two chambers: a lower globe where water is heated, often by a flame, and an upper chamber where the coffee grounds and water will be mixed. Connected to the upper chamber is a siphon tube, which extends almost to the bottom of the globe when assembled. A rubber stopper creates a seal around the tube and the opening to the globe to ensure the steam and vapor pressure is contained. The main working principle of a vacuum brewer is that the final stage of the brewing process, called the draw down, utilizes a partial vacuum created by the lower brewing chamber to "suck" the brewed coffee down through a filter. A siphon brew begins by heating a volume of water in the lower globe, which is then sealed once the upper chamber is set into place. When the seal is created, vapor pressure will begin to build as the air inside the globe is heated, and once steam is produced the pressure inside the globe builds more. Once the pressure is sufficient, the water will begin to be forced up the siphon tube and into the upper bowl, where the coffee grounds will be mixed in and allowed to steep anywhere from 1-5 minutes. During the brewing process, the globe is left on the heat to maintain a positive vapor pressure and bubble gas up the siphon tube. Once the globe is removed from the heat, it will begin to cool and the pressure will drop. At some point, the globe’s internal pressure will fall lower than the atmospheric pressure around it, and thus the brewed coffee will be "sucked" down through the filter at the opening of the siphon tube and back into the lower globe. Like the Clever Dripper, vacuum pot brewing starts as immersion and ends with a bit of percolation at the end, allowing for somewhat quicker brews than pure immersion styles.
A German-made porcelain pour-over drip brewer with a very unique design element: it features a permanent porcelain filter grid, instead of using disposable paper filters. The Walkure brewers brew in a cylindrical column where the ground coffee is added directly to the brew chamber on top of the filter. It is important to select a proper coffee grind which won’t fall through the holes in the filter, though the grounds should have an easy enough time sticking together and staying in the chamber. The user will pour water over a distribution plate, whose flat surface directs the water gently to six holes around its perimeter, where water will trickle steadily onto the grounds below. Walkure brews tend to have heavy body and some sediment, though should be fairly free of loose grounds if brewed correctly. The gentle shower of water limits how much agitation happens in the coffee bed, and thus limits how many fine particles traverse the brew bed and fall into the carafe below. Walkure brewers also take advantage of cake filtration, where the bed of coffee compacts somewhat during brewing and acts as its own filter.
Kalita Wave brewers are basket-style, or truncated cone drippers which feature sloped walls and a flat bottom. They have three holes in the bottom of the dripper and use scalloped or wave-shaped paper filters, which allow even airflow all through the dripper to mitigate stalling during the drain phase. Those three holes also impose a soft limit on the maximum flow rate of water through the dripper, meaning the brew tends to steep a bit as you pour. This also means technique isn’t quite as critical with the Wave as it is with V60s or similarly fast-flowing drippers. Kalita Wave brews often accentuate sweetness and slightly mutes acidity, but produce nonetheless bright and clean coffees.
French PressShop French Press
The french press, or cafetiere, is another classic brewing method with a rich history. Often, it is the stepping stone a home brewer might first take from an automatic coffee maker into the world of manual brewing. French presses are common and easy to find, and similarly easy to use, only requiring a 4-5 minute steep of hot water and grounds and a plunge of the filter to press the grounds to the bottom of the device before serving. As an older and somewhat unrefined brewing method there are some areas of concern, such as the fact that even after pressing, the coffee grounds will continue to extract and alter the flavor of the coffee. Further, most press pots use a metal mesh filter which allows a good deal of mud or silt into the brewed coffee, which can cause off-flavors or poor mouthfeel. Newer revisions of the device include modernized filters with smaller hole sizes, or even dual filters to further restrict continued extraction and sediment.
The original stovetop "espresso" machine. Moka pots function very similarly to vacuum pots, and produce a strong brewed coffee that’s somewhere between drip and espresso. A lower reservoir holds water during brewing, a basket of coffee is inserted into the middle with a siphon tube extending into the lower part of the reservoir, and an upper chamber is used to collect the brewed coffee. During brewing, the water is heated and thus builds vapor pressure in the bottom chamber. This forces hot water up through the coffee grounds, which are lightly packed and ground fairly fine to offer some resistance to the water and allow a quick extraction. The brewed coffee continues to be forced upward until it exits into the upper collection chamber. Once most of the water has been forced up, the moka pot will begin to spit bubbles of gas instead of liquid coffee, and it can be removed from the heat.
In its early days, espresso was brewed in much the same manner, mostly through steam power rather than by the pumps or pistons we use today. At that time, a moka pot essentially was an espresso maker, given the similar brewing process and resulting coffee. However, today espresso has advanced beyond what a moka pot can produce, so despite historically being called an "espresso maker," the moka pot is more of its own category of brewer today. It falls somewhere between drip coffee and espresso in terms of concentration, flavor, and mouthfeel.
Percolation – One of the two primary means of coffee extraction. Percolation refers to the act of moving a liquid (water, in this case) through a bed of soluble material. Many of the most common styles of brewing are considered to be percolation: this includes all drip coffee including pour-over, batch brewing, the Aeropress brewer, moka pots, even espresso. Functionally, percolation is distinct in that new, fresh solvent is constantly added during brewing, meaning extraction can happen more quickly and also may be a little less forgiving.
Immersion – Immersion brewing is the second primary means of coffee extraction. As the name implies, it refers to the immersion of the coffee grounds within the liquid solvent (again, typically water). As an immersion brew progresses, the solvent becomes increasingly saturated with dissolved material, which means that extraction will slow as the brew progresses unless something intervenes. Common immersion brewing styles include french press, cold brew, some Aeropress recipes, and cupping. Interestingly, nearly all immersion methods incorporate a bit of percolation when it comes to separating the liquid from the ground coffee. A french press introduces percolation as the plunger forces the coffee grounds to the bottom, forcing liquid up through a cake of coffee grounds in the process.
Extraction – The act of dissolving chemical compounds out of the coffee grounds and into a solvent, usually water. In coffee, extraction is often interpreted as having "stages," because it contains diverse chemical compounds with different molecular weights. Chemicals with lower molecular weights tend to be more polar and extract most readily – these include acids and some sugars, as well as caffeine. As the brew progresses, more "heavy" compounds enter the mix and shift the flavor balance. Heavier compounds include more complex sugars, other organic acids, and compounds like phenols and other bitter-tasting alkaloids. So, as extraction progresses, the flavor balance typically shifts from sour, to sweeter and more balanced, to more bitter, to very bitter and astringent.
- "Good" extraction – When the flavor balance in the coffee is pleasant, sweet, not too sour or too bitter, and is easy to drink plain (assuming you enjoy black coffee).
- Over-extraction – When the flavor balance in a coffee brew has gone from sweet and/or balanced to bitter, astringent, dry, chalky, oily, woody.
- Under-extraction – The flavor balance has not achieved enough sweetness or bitterness and tastes primarily sour, grassy, bean-like, vegetal, sometimes salty.
Brewing Ratio – Expressed as a ratio of ground coffee mass to brew water mass (for brewed coffee), or ground coffee mass to beverage mass (for espresso). Ratios are generally expressed in nonspecific terms, like 1:16 instead of the equivalent 45:720, as they are intended to be scalable. Ratios are always expressed in mass, usually in grams. They cannot reasonably be converted to volume, because the density of ground coffee is usually unknown. The water component is always the larger number, the denominator. Common brew ratios include 1:15 – 1:17 for brewed coffee, 1:5 – 1:10 for cold brew (which is often brewed strong and intended to be diluted for serving), and 1:1 – 1:2.5 for espresso. For the purposes of coffee brewing, lower values for water/beverage represent "higher" ratios – i.e. the 1:2 ratio often found in espresso brewing is a high ratio and represents a very strong coffee beverage.
Bloom – An initial stage of coffee brewing where a small amount of water is poured onto the grounds to allow them to fully saturate and degas. Fresh coffee, up to about three weeks after roasting, contains CO2 and some other gases trapped within the cellulose structure of the beans. Once saturated with water, these gases release more freely and can cause unevenness in extraction. A bloom phase allows the gas to escape before getting more of the extraction underway. It also helps relieve the gas buildup that might cause the brew bed to overflow as more water is added.
Slurry – The mixture of coffee grounds and water created during brewing. Not typically used to refer to brewing methods where the coffee is more or less held in place, as in espresso brewing, moka pots, or American Press.
Slurry Temperature – The overall temperature of the coffee and water mixture at a given point in time. Slurry temperatures are not usually static, even when the brewing device is insulated, as temperature loss is a natural aspect of coffee brewing. There is some disagreement on what constitutes a proper slurry temperature, however as with most aspects of coffee brewing there is flexibility and most rules are simply rules of thumb. In contemporary specialty coffee culture, it is suggested that the slurry temperature be maintained within 195-205 F – however, this is sometimes a mis-attribution in reference to the Specialty Coffee Association of America’s Golden Cup standards. Those standards actually suggest a water temperature between 195-205 F at the moment of contact with the coffee grounds, and do not reference slurry temperature at all. Indeed, given that water temperature, the slurry temperature would likely be 10-15 degrees cooler throughout the brew thanks to heat lost to the coffee grounds, the brewing device, and to the air. Still, there is no wrong method of approaching coffee extraction, so theoretically the contemporary interpretation is just as valid as the SCAA’s standards.
PID – A digital controller typically used for setting a desired temperature in a kettle or water boiler. Stands for Proportional, Integral, Derivative, the logical functions used by the controller to set and hold the desired temperature based on feedback from a thermocouple or RTD sensor.
Espresso – A short, strong serving of coffee brewed under pressure. Espresso is characterized by its high brew strength, viscous mouthfeel, and its signature layer of foam on top, known as "crema." Crema can be a fairly good indicator of the quality of an espresso, because its formation relies on proper extraction pressure, good coffee freshness, and it provides some visual indication of flaws like channeling and over-extraction. Espresso is typically served in volumes of 1-3 fl oz, depending on the style of preparation and the number of "shots" being prepared.
Ristretto – A ristretto espresso is one pulled intentionally short to intensify the flavor. Sometimes this is done so the coffee flavor is more pronounced in a milk drink or mixed drink, but it is also considered desirable for certain coffee blends to intensify the sweetness and concentration of the shot. In terms of brewing ratio, a ristretto is commonly defined as a shot pulled at 1:1 - 1:1.5 (grounds mass:beverage mass).
Normale – As the name implies, a normale espresso is essentially normal, the standard version of a shot. In Italy the rules of thumb for a normale are 7 grams of ground coffee for a single and 14 grams for a double, pulled to around 25-30 mL for a single and 50-60 mL for a double. In more modern terms, a normale has a brew ratio around 1:2 (ground coffee mass:beverage mass). A normale shot is meant to be fairly well-balanced, with good mouthfeel, aroma, and sweetness. This may not be a term which is encountered all that often, even within Italy where it originated.
Lungo – A lungo espresso is a shot pulled longer than normal. A longer extraction will increase the volume of the shot, and may also subdue some of the flavors to make for a more sippable espresso. In terms of ratio, a lungo is generally pulled at around 1:3 or more (grounds mass:beverage mass).
Macchiato – Means "marked" or "spotted" in Italian. This is a shot of espresso with a small amount of steamed milk added to help round out the flavor of the shot and add slight sweetness. In some interpretations, the shot is marked with only a spoonful of foam, while in others the demitasse is topped up with steamed milk and may have a small latte art design on top. In all cases, this is a very small beverage, between 1.5-3 fl oz. Some modern cafes offer a macchiato as a "one and one": an espresso pull split into two demitasses, one served plain and one served with steamed milk so the customer may enjoy the espresso both ways.
Espresso + Milk – Many variations of espresso and steamed milk exist across the world, and many similar beverages go by different names. It is difficult to find complete agreement on any given recipe, and in fact some cafe owners have decided to omit drink names entirely and simply offer menu items as "Espresso with milk" in a few different sizes. The differences between some drinks are very subtle, relying on the texture of the steamed milk, overall volume of the espresso shot, or even the type of cup the drink is served in to create distinction. As such, the definitions included below for espresso and milk drinks should be considered to be loose and flexible.
Cortado/Gibraltar/Piccolo Latte – A very small drink made with espresso and steamed milk, with a light layer of foam on top. Not every cafe will consider these three drinks to be the same, but they are often prepared quite similarly and just as often are indistinct from each other. The Gibraltar is named specifically for the glass it is served in: a small rocks glass from Libbey’s Gibraltar series of glassware. Usually the overall volume of these drinks is between 5-6 fl oz, and they are often made with a double shot of espresso for a strong coffee flavor. Often these drinks are served in small rocks glasses, but may be served in ceramic as well.
Cappaccino – A small drink made with espresso and steamed milk, characterized by its cap of dense foam. A common rule of thumb for cappuccinos is that they should be a drink of thirds: one third espresso, one third steamed milk, and one third dense foam, by volume. For a 2 fl oz shot of espresso, this makes for a 6 fl oz beverage total. Interpretations of the cappuccino vary, and especially with the popularity of microfoam in milk beverages some cappuccinos will have thinner but dense foam caps, while others prepare theirs with airy, fluffy foam piled high. Some countries also prepare their cappuccinos by adding chocolate powder to the espresso before adding the milk.
Flat White – A small drink made with espresso and steamed milk. The actual definition of a flat white is somewhat contentious, and even in Australia and New Zealand where the drink originates there is enough variation to be confusing (a trait shared among many espresso and milk drinks). Commonly offered characteristics for the flat white include the use of a ristretto shot or single shot, a total of 5-6 fl oz for the beverage, and only the slightest layer of milk foam being present. In some countries, there isn’t much of a difference between this and a cortado, or even a cappuccino, but it may be found on menus all over the world regardless.
Latte – A larger drink made with espresso and steamed milk, properly a "caffe latte" in Italian. With no strict definition for the ratio between espresso and steamed milk, this is a highly variable beverage whose chief characteristic is the overall milky flavor. It also features less foam than a cappuccino with a thinner overall texture. Flavored lattes are also quite popular, with syrups, spices, or other flavorings being mixed into the espresso or milk when assembling the drink. In some countries, a latte is specifically served in a tall glass rather than ceramic.
Green coffee – Unroasted coffee, the seed of the coffee berry which has been processed and dried to prepare it for roasting.
Chaff – Chaff is a product of roasting, comprised of the silverskin or epidermis of the coffee seeds. During roasting, this thin, papery layer of cellulose loses its moisture and begins to flake or peel off the coffee beans. Coffee roasters will often have means of catching or diverting the chaff away from the beans, as it can be prone to catching fire if heated sufficiently. Some chaff may remain attached to the beans after roasting is completed. While chaff is entirely flavorless and will not affect coffee brewing, it may be considered troublesome as it has a tendency to fly away from the coffee grounds and stick to items thanks to static.
Drum roaster – A roasting device which uses a large, rotating drum set horizontally to continuously agitate the beans. Drum roasters apply heat in a variety of ways, some using gas burners to heat the drum material, some heating the air which is forced through the drum, some combining both. Others might use electric heating elements rather than gas burners. The agitation of the beans helps to ensure a more even roast of the coffee beans, as they do not sit still long enough to receive too much heat, or have an uneven exposure to the heat relative to other beans in the batch. Drum roasters are the most common style of roaster used today, though their other technical attributes will vary by manufacturer and model, sometimes in significant ways.
Fluid bed (air) roaster – A fluid bed roaster uses a hot column of air to both roast and agitate the beans. Fluid bed roasters are not all that common in commercial use, but are popular with home hobby roasters as they can be found in the form of an inexpensive home appliance: the hot air popcorn maker. Fluid bed roasts tend to take far less time than other roasting methods, as the air has a good deal of access to the surface area of the beans, and must be kept at significantly high temperatures to prevent "baking" the beans and progress the chemical reactions which are part of roasting. Roasting in this manner has some drawbacks, such as that it often yields coffees which are more acidic at a given roast level than another roaster might produce. They are also somewhat more difficult to control for roast profiling, again because they progress more quickly given the temperatures required for adequate roasting.
Degree of roasting (lightness or darkness) – Roasting degree describes the stopping point of the roast, which has some impact on the flavor of the brewed coffee. Often described on a scale from light to dark, there are many stopping points on the scale which have their own given names, such as "Cinnamon roast," "full city," or "French roast." Not all roast degree descriptions have agreed-upon criteria, and some degrees have multiple accepted names. Further, the degree of roast is only part of what factors into coffee flavor, and the roast profile also matters some.
Roast profiling – A roast profile is comprised of the cumulative effects of how heat and airflow are controlled during the roasting process, which influence how quickly the beans are heated and progress through the stages of roasting. The roast profile is arguably the defining factor for how roasting contributes to the coffee’s flavor, as it determines how the chemical changes take place in the coffee, for how long, as well as when the roasting process is fully stopped. Profiles are typically data-driven, using the thermal information from inside the roaster as well as the data from the roasting controls such as gas, airflow, drum temperature, etc. A profile is usually a complex system of data which encompasses as much information about the coffee’s transition from green to roasted as possible, such that it may be replicated in future roasts, or tweaked based on feedback from the cupping table.
Plant Type Terms
Coffee plant – The coffee plant is a member of the Rubiaceae family, related to cinchona and some types of gardenia. It is a tropical flowering shrub or tree, which produces fruits called "cherries" or "berries" (botanically, they are neither). Coffee plants have a woody trunk, long slender branches with many wide and flat waxy leaves. Leaf size and shape depends on species and variety, but they are often football-shaped and sometimes slightly pointed. Coffee plants produce groups of white blossoms, which are highly fragrant and smell somewhat similar to jasmine. The fruits are small, about the size of grapes, and can take 6-10 months to fully ripen. They are edible and fleshy but contain little pulp, and contain two seeds. Those seeds are what we commonly call "beans," which are removed from the ripe fruit, then processed and dried into what we call green coffee. The plants grow best within the Tropics, which we affectionately call the Bean Belt. Coffee can grow in a range of conditions, from low-altitude islands to high in the mountains of Peru. Generally, the higher the altitude in which the coffee is grown, the denser the seeds are, and the more potent the acidity and flavor (not always desirable).
Arabica – Coffea arabica. The primary species of coffee grown for specialty coffee, considered to have the most desirable flavor of coffee species. Arabica plants take about 3-5 years to fully mature and start producing fruit, and some varieties are quite delicate and susceptible to disease, environmental conditions, and pests.
Robusta – Coffea canephora. Seen as inferior in flavor to arabica, often described as overly bitter, tasting of petroleum or rubber. Robusta has a naturally higher caffeine content than arabica, and is also a hardier and more productive plant. Because the flavor quality is poor, it is usually used only as a small component in blended coffees and is rarely drank on its own (though some cultures do enjoy its potent and strong flavor).
Other species – Other coffee species are far less common, but some interest in cultivating them has increased in the past few decades in order to obtain more genetic diversity in coffee crops. These include but are not limited to coffea liberica, coffea charrieriana (which is naturally caffeine-free), and coffea magnistipula.
Variety/cultivar – A variety is a recognized type of coffee, a taxonomic subset within a species (think of how a cherry tomato and a plum tomato are the same species, but different in size, shape and flavor). In coffee, there are naturally occurring, selected, and genetically hybridized varieties. A cultivar, or "cultivated variety," is similar to a variety, but specifically refers to selected varieties where human intervention created or honed a variety. Note: "Varietal" is sometimes erroneously used instead of variety – for reference, varietal is an adjective, variety is a noun. "Varietal" may be used as a noun in shorthand, in reference to a "varietal coffee," or a coffee which is comprised of only one specific variety, similar to how the term is used in the wine world.
"Specialty" is an industry-defined term for green coffees graded at 80 points or above (out of 100), which is currently the highest categorical grade of coffee achievable. Specialty coffees must have zero Category 1 defects (such as rotten beans, fungus damage, etc) and fewer than five Category 2 defects (such as partially black, partially sour, broken beans, or insect damage) per 350 gram sample. In terms of market share, specialty coffees comprise under 10% of coffee grown annually, but represent over 50% of the US market consumption of coffee. The term "specialty" does not account for what happens after the grading of green coffee, so it technically applies to any use of said coffee afterward, whether roasted light or dark, or served black or as part of a blended beverage. "Specialty coffee" is also, confusingly, used as a marketing term to refer to fancy or gourmet coffee beverages served at coffee shops.
Threats to Coffee Plants
Coffee Berry Borer – The coffee berry borer is a pest beetle native to Africa which can cause massive devastation to coffee crops. The small insect chews holes throughout the fruit and seed to lay its eggs, causing rot to occur prematurely, as well as introducing foreign bacteria into the young coffee seed. This inevitably leads to taste defects and can reduce a promising coffee to a much lower grade. Pesticides are only effective if used on the berries prior to the female beetle tunneling inside.
Coffee leaf rust – Coffee rust, or "roya" in Spanish, is a critical problem for many farmers in South and Central America. It is a fungus which infests the leaves of the coffee plant and causes defoliation, the loss of leaves as the plant tries to save itself from the disease. Because leaves are how plants respire and create nutrients through photosynthesis, defoliation is a critical problem for the plants and for the farmers, as a coffee plant will not produce fruit if it needs to regenerate itself after being affected by leaf rust. Leaf rust is resistant to some types of fungicide, and many arabica plants are highly susceptible to the disease because they lack the genetic defense against it taking hold.
Harvesting & Processing
harvesting – Most coffee is harvested entirely by hand, which is optimal as the coffee cherries do not ripen uniformly and coffee tastes best when picked at peak ripeness. Manual harvesting is labor-intensive and grueling as farms are often located on steep mountainsides and in rainforests, and many workers are paid by the pound rather than for their time. Some larger plantations and commodity-grade operations do use mechanical harvesting methods, which incorporate the use of large machines which drive up and down the rows of coffee plants, shaking the trees and collecting whatever falls off – generally including a mix of under-ripe, ripe, and over-ripe fruit, which tends to contribute to the lower grade of their produce.
Processing – After harvesting, the coffee cherries must be processed to remove the seeds from within. There are multiple methods of processing fruit into dry seeds, with multiple steps including depulpling, fermentation, drying, de-husking, secondary drying, and finally collection, packaging, and grading. The fruit is sometimes discarded, sometimes it is retained for compost and fertilizer, and rarely it is processed and dried separately for a tea-like drink call cascara or qishir.
- Wet/washed processing – Wet or washed processing involves the use of water through many steps of the coffee processing, and is considered to produce some of the highest quality coffees thanks to the clarity of flavors with few defects. It is also more resource-intensive and sometimes impractical or too expensive for a farm, processor, mill, or cooperative to perform. This begins by running the whole coffee cherries through troughs of water to separate the desirable (sinking) cherries from the undesirable (floating) cherries, as well as from sticks and leaves that have been mixed in with the cherries. Those ripe cherries are then sent for de-pulping, which is often done mechanically using a device which squeezes the fruit to break the fruit’s skin and pop out the seeds within through a screen with holes just big enough for the seeds to get through. The sticky mucilage is still attached to the seeds at this point, though some will be washed off with water. The seeds are then fermented in tanks for about a day, where bacteria and yeasts will break down the sugars in the mucilage and may influence the flavor of the coffee. After fermentation, the seeds may be washed again, and are then taken to dry. Drying may be done on large concrete patios, in full sun or under canopies, it may also be done on raised screen beds, inside climate-controlled greenhouses, or in large tumbling chambers to be dried by forced hot air. Once the coffee is sufficiently dried (to about 10-15% moisture content), it is de-hulled. The coffee seeds have up until now resided in parchment (pergamino in Spanish), a stiff outer coating like a sunflower seed’s shell. The shell is cracked off mechanically to extrude the green coffee seeds inside. Those seeds are then packaged in large sacks, and will be graded following the Specialty Coffee Association protocol to determine their market value prepare them for sale.
- Semi-washed, pulped natural, honey process – These terms often refer to the same style of processing, where the first stages of the above are followed up until the cherries are pulped. Then, instead of fermenting the coffee in tanks, it is sent to be dried while the mucilage is still intact and stuck to the seeds. As the seeds dry, the mucilage loses a good deal of moisture but can contribute a greater degree of sweetness to the seeds (perhaps because less fermentation is taking place, meaning fewer sugars are being consumed by microorganisms). Once dried, the seeds may be washed to remove the stuck on pulp, or simply proceed to de-hulling. The green coffee seeds may also be dried again to reach the desired moisture content, as drying coffee in this state can take longer than the washed process. This process can also introduce complications that lead to flavor degradation, including mold growth, rot, and pests which are attracted to the sweet-tasting mucilage as it dries in the open air. These coffees must be carefully attended to during drying to properly maintain their flavor.
- Natural/dry processing – In natural processing, rather than washing and de-pulping the cherries, instead the whole fruit is slowly dried with the seeds inside. This is a long process which can lead to many undesirable flavors and defects, but when done right can yield unmistakably sweet and fruity flavors like blueberry, strawberry, and raspberry, as well as a slightly vinegary flavor due to acetic acid production by bacteria during drying. Once the fruit is dried, it is pulped (not always with water present) and de-hulled at the same time. Sometimes seeds may be further dried afterward. As this processing method is least resource-intensive, it is often preferred by smaller farm or poorer producing countries, such as Ethiopia and Yemen.
Fermentation – Fermentation in coffee is a part of the processing of the coffee seeds, where microorganisms and enzymes are allowed to break down and process parts of the coffee seeds. Typically fermentation is used to break down the mucilage, a sticky part of the coffee fruit which coats the coffee seeds. Bacteria and yeasts may digest the carbohydrates in the mucilage, producing gas and acids as byproducts, while also breaking the mucilage down for easier removal. In more recent years, careful examination and experimentation with the fermentation process has revealed that it can have strong influences on coffee flavor, though not always in a desirable way.
Grading & Other
Q Grading – Once processed into its dry green state, coffee may be analyzed by certified Q graders, professionals whose job it is to evaluate coffee and determine its market value. Q graders are employed in a variety of ways, sometimes by importing companies, sometimes by local governments, authorities, or auction houses, sometimes by coffee roasters with direct relationships with the farmers they purchase from. The purpose of Q grading is to evaluate, in as standardized a fashion as possible, the quality of the coffee present. Q graders use standardized cupping practices and protocols, standard evaluation forms and criteria, in order to make conclusions about the coffee quality. Coffee is scored on the presence of defects such as insect damage, fungus, over- or under-ripeness, undeveloped seeds called quakers, and so on. It is also scored on flavor by roasting to a standard specification and noting the presence and balance of the acidity, sweetness, bitterness, the quality of the aroma, the finish, the aftertaste, the body, etc. Points are assigned or deducted based on these findings, and a particular coffee is usually cupped and scored multiple times before settling on an adjusted score. Specialty coffees are those graded at 80 points or above (out of 100), with 0-5 total defects per 350 gram sample. After grading, coffees may be sent to special auctions, sold directly to green coffee buyers or to central distribution warehouses in the country of origin.
Coffee eaten and excreted by the Asian Palm Civet, which partially digests the beans and theoretically has some kind of positive effect on flavor. Given the rarity of finding civet droppings in the wild and the need to collect them by hand, kopi luwak originally garnered an exceptionally high price due to labor and the draw of a smoother tasting cup. Today, however, the industry has turned more to caging the animals and feeding them only coffee berries (not typical of their natural diet). Many animal rights watchdogs consider this to be abusive of the animals, so there’s been backlash against the coffee and the industry which provides it. For practical purposes, it is probably best to seek out those producers which can ensure the safety and quality of life of their animals, but even then, it is likely far overpriced for its quality and other high quality coffees from other origins can be had for much less. There is also some work being done to replicate the enzymatic activity from the civet’s gut in a lab environment to create an animal-free alternative with the same sort of flavor.
"Waves" of Coffee
It’s commonly accepted that we are currently seeing the "third wave" of coffee throughout the world, an approach to coffee preparation, presentation, and service which is distinct from the two previous waves. The defining factors are a little fuzzy, as a few people are attributed to having coining the term and defining the waves. One source for definitions which is commonly cited is a piece by industry veteran Trish Rothgeb in The Flamekeeper, a trade magazine for the Roasters Guild of America.
First wave coffee is loosely defined as coffee without focus. Prior to the latter half of the 20th century coffee was often treated solely as a beverage to drink with breakfast, after dinner, perhaps on a late night of work. It could be good or bad, but it didn’t receive the same sort of care and attention it does today. This is the historical idea of coffee, a beverage with tradition imbued into it and regional styles and techniques, even its own culture which draws from its relevance as a trade good over centuries. First wave coffee could be summarized as diner or restaurant coffee, or by brands like Folgers.
Second wave coffee is where we began to see the rise of the modern coffee shops. Many cultures already had coffee shops prior to the second wave, but they were "old world," much like a pub but focused on coffee and lighter fare instead. The modern second wave cafe is more akin to the Central Perk cafe from Friends: a shop dedicated to coffee and tea beverages, including richly flavored lattes, frothy cappuccinos, and so on. Often these are places with space built out for lingering over a book or a laptop, sometimes they act as venues for music or poetry. The coffee quality is perhaps not the best, but the atmosphere is inviting and casual. The concept of the "third place," a place outside of the home and work where a person might spend much of their time, heavily influenced the rise of the second wave coffee shop. Second wave coffee could be summarized by shops like Starbucks and Peet’s (though they are not limited solely to second wave).
Third wave coffee is where coffee is meant to be elevated to the culinary level of appreciation, like fine wine or beer. It recognizes that coffee is a complex beverage which requires care and attention to execute on a high level, and can provide a rich and complex experience beyond adding flavored syrups or mix-ins (not that those are eschewed, however). Third wave coffee is concerned with specialty coffee only, and extends its focus to the entire process from the farm to the cup. Farm and farmers are sometimes highlighted for transparency purposes, as well as to shed light on the importance of proper growing, picking, processing, etc. on the results in the final cup. Third wave roasters often roast and develop their coffees rather lightly, with the intention of putting acidity, sweetness, florality, fruitiness, and the innate complexity of the coffee at the forefront, rather than flavors created by the roasting process.