Coffeemaker

Vacuum brewers

Other coffee brewing devices became popular throughout the nineteenth century, including various machines using the vacuumm principle. The Napier Vacuum Machine, invented in 1840, was an early example of this type. While generally too complex for everyday use, vacuum devices were prized for producing a clear brew, and were popular up until the middle of the twentieth century.

The principle of a vacuum brewer was to heat water in a lower vessel until expansion forced the contents through a narrow tube into an upper vessel containing ground coffee. When the lower vessel was empty and sufficient brewing time had elapsed, the heat was removed and the resulting vacuum would draw the brewed coffee back through a strainer into the lower chamber, from which it could be decanted. The Bauhaus interpretation of this device can be seen in Gerhard marcks’ Sintax coffee maker of 1925.

An early variant technique, called a balance siphon, was to have the two chambers arranged side-by-side on a sort of scale-like device, with a counterweight attached opposite the initial (or heating) chamber. Once the near-boiling water was forced from the heating chamber into the brewing one, the counterweight was activated, causing a spring-loaded snuffer to come down over the flame, thus turning "off" the heat, and allowing the cooled water to return to the original chamber. In this way, a sort of primitive 'automatic' brewing method was achieved.

On August 27, 1930, Inez H. Pierce of Chicago, Illinois filed patent for the first vacuum coffee maker that truly automated the vacuum brewing process, while eliminating the need for a stove top burner or liquid fuels. An electrically-heated stove was incorporated into the design of the vacuum brewer. Water was heated in a recessed well, which reduced wait times and forced the hottest water into the reaction chamber. Once the process was complete, a thermostat using bi-metallic expansion principles shut off heat to the unit at the appropriate time. Pierce’s invention was the first truly "automatic" vacuum coffee brewer, and was later incorporated in the Farberware Coffee Robot.

Pierce’s design was later improved by U.S. appliance engineers lvar jepson, Ludvig Koci, and Eric Bylund of Sunbeam in the late 1930s. They altered the heating chamber and eliminated the recessed well which was hard to clean. they also made several improvements to the filtering mechanism. Their improved design of plated metals, styled by industrial designer Alfonso lannelli, became the famous Sunbeam Coffeemaster line of automated vacuum coffee makers (Models C-20, C-30, C40, and C-50). The Coffeemaster vacuum brewer was sold in large numbers in the United States during the years immediately following World war II.

Percolators

Percolators began to be developed from the mid-nineteenth century. In the United States, James Nason of Massachusetts patented an early percolator design in 1865. An Illinois farmer named Hanson Goodrich is generally credited with patenting the modern percolator. Goodrich's patent was granted on August 16, 1889, and his patent description varies little from the stovetop percolators sold today. With the percolator design, water is heated in a boiling pot with a removable lid, until the heated water is forced through a metal tube into a brew basket containing coffee. The extracted liquid drains from the brew basket, where it drips back into the pot. This process is continually repeated during the brewing cycle until the liquid passing repeatedly through the grounds is sufficiently steeped. A clear sight chamber in the form of a transparent knob on the lid of the percolator enables the user to judge when the coffee has reached the proper color and strength.

Domestic electrification simplified the operation of percolators by providing for a self-contained, electrically-powered heating element that removed the need to use a stovetop burner. A critical element in the success of the electric coffee maker was the creation of safe and secure fuses and heating elements. In an article in House Furnishing Review, May 1915, Lewis Stephenson of Landers, Frary and Clark described a modular safety plug being used in his company’s Universal appliances, and the advent of numerous patents and innovations in temperature control and circuit breakers provided for the success of many new percolator and vacuum models. While early percolators had utilized all-glass construction (prized for maintaining purity of flavor),

The method for making coffee in a percolator had changed very little since its introduction in the early part of the 20th century. However, in 1970 General Food Corporation introduced Max Pax, the first commercially available "ground coffee filter rings”. The Max Pax filters were named so as to compliment General Foods' Maxwell House coffee brand. The Max Pax coffee filter rings were designed for use in percolators, and each ring contained a pre-measured amount of coffee grounds that were sealed in a self-contained paper filter. The sealed rings resembled the shape of a doughnut, and the small hole in the middle of the ring enabled the coffee filter ring to be placed in the metal percolator basket around the protruding convection (percolator) tube.

Prior to the introduction of pre-measured self-contained ground coffee filter rings; fresh coffee grounds were measured out in scoopfuls and placed into the metal percolator basket. This process enabled small amounts of coffee grounds to leak into the fresh coffee. Additionally, the process left wet grounds in the percolator basket, which were very tedious to clean. The benefit of the Max Pax coffee filter rings was two-fold: First, because the amount of coffee contained in the rings was pre-measured, it negated the need to measure each scoop and then place it in the metal percolator basket. Second, the filter paper was strong enough to hold all the coffee grounds within the sealed paper. After use, the coffee filter ring could be easily removed from the basket and discarded. This saved the consumer from the tedious task of cleaning out the remaining wet coffee grounds from the percolator basket.

With the introduction of the electric drip coffee maker for the home in the early 1970's, the popularity of percolators plummeted, and so did the market for the self-contained ground coffee filters. In 1976, General Foods discontinued the manufacture of Max Pax, and by the end of the decade, even generic ground coffee filter rings were no longer available on U.S. supermarket shelves.

 

Electric drip coffeemakers

An electric drip coffee maker can also be referred to as a dripolator. It normally works by admitting water from a cold water reservoir into a flexible hose in the base of the reservoir leading directly to a thin metal tube or heating chamber (usually, of aluminum), where a heating element surrounding the metal tube heats the water. The heated water moves through the machine using the thermosiphon principle. Thermally-induced pressure and siphoning effect move the heated water through an insulated rubber or vinyl riser hose, into a spray head, and onto the ground coffee, which is contained in a brew basket mounted below the spray head. The coffee passes through a filter and drips down into the carafe. A one-way aromalock valve in the tubing prevents water from siphoning back into the reservoir. A thermostat attached to the heating element turns off the heating element as needed to prevent overheating the water in the metal tube (overheating would produce only steam in the supply hose), then turns back on when the water cools below a certain threshold. For a standard 10-12 cup drip coffeemaker, using a more powerful thermostatically-controlled heating element (in terms of wattage produced), can heat increased amounts of water more quickly using larger heating chambers, generally producing higher average water temperatures at the spray head over the entire brewing cycle. This process can be further improved by changing the aluminum construction of most heating chambers to a metal with superior heat transfer qualities, such as copper.

Throughout the latter part of the 20th century, a number of inventors patented various coffeemaker designs using an automated form of the drip brew method. Subsequent designs have featured changes in heating elements, spray head, and brew-basket design, as well as the addition of timers and clocks for automatic-start, water filtration, filter and carafe design, and even built-in coffee grinding mechanisms.

Pourover, water displacement drip coffeemakers

Bunn-O-Matic also came out with a different drip-brew machine. In this type of coffeemaker, the machine uses a holding tank or boiler pre-filled with water. When the machine is turned on, all of the water in the holding tank is brought to near boiling point (approximately 200-207 °F or 93-97 °C) using a thermostatically-controlled heating element. When water is poured into a top-mounted tray, it descends into a funnel and tube which delivers the cold water to the bottom of the boiler. The less-dense hot water in the boiler is displaced out of the tank and into a tube leading to the spray head, where it drips into a brew basket containing the ground coffee. The pourover, water displacement method of coffeemaking tends to produce brewed coffee at a much faster rate than standard drip designs. Its primary disadvantage is increased electricity consumption in order to preheat the water in the boiler. Additionally, the water displacement method is most efficient when used to brew coffee at the machine's maximum or near-maximum capacity, as typically found in restaurant or office usage.

Design considerations in coffeemakers

At the beginning of the twentieth century, although some coffee makers tended to uniformity of design (particularly stovetop percolators), others displayed a wide variety of styling differences. In particular, the vacuum brewer, which required two fully separate chambers joined in an hourglass configuration, seemed to inspire industrial designers. Interest in new designs for the vacuum brewer revived during the American arts & Crafts movement with the introduction of "Silex" brand coffee makers, based on models developed by Massachusetts housewives Ann Bridges and Mrs. Sutton. Their use of Pyrex solved the problem of fragility and breakability that had made this type of machine commercially unattractive. During the 1930s, simple, clean forms, increasingly of metal, attracted positive attention from industrial designers heavily influenced by the functionalist imperative of the Bauhaus and Streamline movements. It was at this time that Sunbeam's sleek Coffeemaster vacuum brewer appeared, styled by the famous industrial designer Alfonso lannelli. The popularity of glass and Pyrex globes temporarily revived during the Second World War, since aluminum, chrome, and other metals used in traditional coffee makers became restricted in availability.

The impact of science and technological advances as a motif in post-war design was eventually felt in the manufacture and marketing of coffee and coffee-makers. Consumer guides emphasized the ability of the device to meet standards of temperature and brewing time, and the ratio of soluble elements between brew and grounds. The industrial chemist Peter Schlumbohm expressed the scientific motif most purely in his "Chemex" coffeemaker, which from its initial marketing in the early 1940s used the authority of science as a sales tool, describing the product as "the Chemist’s way of making coffee", and discussing at length the quality of its product in the language of the laboratory: “the funnel of the CHEMEX creates ideal hydrostatic conditions for the unique...Chemex extraction.” Schlumbohm’s unique brewer, a single Pyrex vessel shaped to hold a proprietary filter cone, resembled nothing more than a piece of laboratory equipment, and surprisingly became popular for a time in the otherwise heavily automated, technology-obsessed 1950s household.

In later years, coffeemakers began to adopt more standardized forms commensurate with a large increase in the scale of production required to meet postwar consumer demand. Plastics and composite materials began to replace metal, particularly with the advent of newer electric drip coffeemakers in the 1970s. During the 1990s, consumer demand for more attractive appliances to complement expensive modern kitchens resulted in a new wave of redesigned coffeemakers in a wider range of available colors and styles.

Coffee processing

Picking

A coffee plant usually starts to produce flowers 3–4 years after it is planted, and it is from these flowers that the fruits of the plant (commonly known as coffee cherries) appear, with the first useful harvest possible around 5 years after planting. The cherries ripen around eight months after the emergence of the flower, by changing colour from green to red, and it is at this time that they should be harvested. In most coffee-growing countries, there is one major harvest a year; though in countries like Colombia, where there are two flowerings a year, there is a main and secondary crop.

In most countries, the coffee crop is picked by hand, a labor-intensive and difficult process, though in places like Brazil, where the landscape is relatively flat and the coffee fields immense, the process has been mechanized. Whether picked by hand or by machine, all coffee is harvested in one of two ways:

Strip Picked: The entire crop is harvested at one time. This can either be done by machine or by hand. In either case, all of the cherries are stripped off of the branch at one time.

Selectively Picked: Only the ripe cherries are harvested and they are picked individually by hand. Pickers rotate among the trees every 8 – 10 days, choosing only the cherries which are at the peak of ripeness. Because this kind of harvest is labor intensive, and thus more costly, it is used primarily to harvest the finer arabica beans.

The labourers who pick coffee by hand receive payment by the basketful. As of 2003^[update], payment per basket is between US$2.00 to $10 with the overwhelming majority of the labourers receiving payment at the lower end. An experienced coffee picker can collect up to 6-7 baskets a day. Depending on the grower, coffee pickers are sometimes specifically instructed to not pick green coffee berries since the seeds in the berries are not fully formed or mature. This discernment typically only occurs with growers who harvest for higher end/specialty coffee where the pickers are paid better for their labour. Mixes of green and red berries, or just green berries, are used to produce cheaper mass consumer coffee beans, which are characterized by a displeasingly bitter/astringent flavor and a sharp odor. Red berries, with their higher aromatic oil and lower organic acid content, are more fragrant, smooth, and mellow. As such coffee picking is one of the most important stages in coffee production.

 

Processing

Wet process

In the Wet Process, the fruit covering the seeds/beans is removed before they are dried. Coffee processed by the wet method is called wet processed or washed coffee. The wet method requires the use of specific equipment and substantial quantities of water.

The coffee cherries are sorted by immersion in water. Bad or unripe fruit will float and the good ripe fruit will sink. The skin of the cherry and some of the pulp is removed by pressing the fruit by machine in water through a screen. The bean will still have a significant amount of the pulp clinging to it that needs to be removed. This is done either by the classic ferment-and-wash method or a newer procedure variously called machine-assisted wet processing, aquapulping or mechanical demucilaging:

Ferment-and-Wash Method: In the ferment and wash method of wet processing the remainder of the pulp is removed by breaking down the cellulose by fermenting the beans with microbes and then washing them with large amounts of water. Fermentation can be done with extra water or, in "Dry Fermentation", in the fruit's own juices only.

The fermentation process has to be carefully monitored to ensure that the coffee doesn't acquire undesirable, sour flavours. For most coffees, mucilage removal through fermentation takes between 24 and 36 hours, depending on the temperature, thickness of the mucilage layer and concentration of the enzymes. The end of the fermentation is assessed by feel, as the parchment surrounding the beans loses its slimy texture and acquires a rougher "pebbly" feel. When the fermentation is complete, the coffee is thoroughly washed with clean water in tanks or in special washing machines.

Machine-assisted wet processing: In machine-assisted wet processing, fermentation is not used to separate the bean from the remainder of the pulp; rather, this is done through mechanical scrubbing. This process can cut down on water use and pollution since ferment and wash water stinks. In addition, removing mucilage by machine is easier and more predictable than removing it by fermenting and washing. However, by eliminating the fermentation step and prematurely separating fruit and bean, mechanical demucilaging can remove an important tool that mill operators have of influencing coffee flavor. Furthermore, the ecological criticism of the ferment-and-wash method increasingly has become moot, since a combination of low-water equipment plus settling tanks allows conscientious mill operators to carry out fermentation with limited pollution.

Any wet processing of coffee produces coffee wastewater which can be a pollutant. Around 130 liters of fresh water is required to process one kilogram of quality coffee

After the pulp has been removed what is left is the bean surrounded by two additional layers, the silver skin and the parchment. The beans must be dried to a water content of about 10% before they are stable. Coffee beans can be dried in the sun or by machine but in most cases it is dried in the sun to 12-13% moisture and brought down to 10% by machine. Drying entirely by machine is normally only done where space is at a premium or the humidity is too high for the beans to dry before mildewing.

When dried in the sun coffee is most often spread out in rows on large patios where it needs to be raked every six hours to promote even drying and prevent the growth of mildew. Some coffee is dried on large raised tables where the coffee is turned by hand. Drying coffee this way has the advantage of allowing air to circulate better around the beans promoting more even drying but increases cost and labor significantly.

After the drying process (in the sun and/or through machines), the parchment skin or pergamino is thoroughly dry and crumbly, and easily removed in the Hulling process. Coffee occasionally is sold and shipped in parchment or en pergamino, but most often a machine called a huller is used to crunch off the parchment skin before the beans are shipped.

Dry process

Dry process, also known as unwashed or natural coffee, is the oldest method of processing coffee. The entire cherry after harvest is first cleaned and then placed in the sun to dry on tables or in thin layers on patios:

Cleaning: The harvested cherries are usually sorted and cleaned, to separate the unripe, overripe and damaged cherries and to remove dirt, soil, twigs and leaves. This can be done by winnowing, which is commonly done by hand, using a large sieve. Any unwanted cherries or other material not winnowed away can be picked out from the top of the sieve. The ripe cherries can also be separated by flotation in washing channels close to the drying areas.

Drying: The coffee cherries are spread out in the sun, either on large concrete or brick patios or on matting raised to waist height on trestles. As the cherries dry, they are raked or turned by hand to ensure even drying and prevent mildew. It may take up to 4 weeks before the cherries are dried to the optimum moisture content, depending on the weather conditions. On larger plantations, machine-drying is sometimes used to speed up the process after the coffee has been pre-dried in the sun for a few days.

The drying operation is the most important stage of the process, since it affects the final quality of the green coffee. A coffee that has been overdried will become brittle and produce too many broken beans during hulling (broken beans are considered defective beans). Coffee that has not been dried sufficiently will be too moist and prone to rapid deterioration caused by the attack of fungi and bacteria.

The dried cherries are stored in bulk in special silos until they are sent to the mill where hulling, sorting, grading and bagging take place. All the outer layers of the dried cherry are removed in one step by the hulling machine.

The dry method is used for about 95% of the Arabica coffee produced in Brazil, most of the coffees produced in Ethiopia, Haiti and Paraguay, as well as for some Arabicas produced in India and Ecuador. Almost all Robustas are processed by this method. It is not practical in very rainy regions, where the humidity of the atmosphere is too high or where it rains frequently during harvesting.

 

Semi dry process

Semi dry is a hybrid process used in Indonesia and Brazil. In Indonesia, the process is also called "wet hulled", "semi-washed" or " Giling Basah". Literally translated from Indonesia, Giling Basah means "wet grinding".

Most small-scale farmers in Sumatra, Sulawesi, Flores and Papua use the giling basah process. In this process, farmers remove the outer skin from the cherries mechanically, using locally built pulping machines. The coffee beans, still coated with mucilage, are then stored for up to a day. Following this waiting period, the mucilage is washed off and the parchment coffee is partially dried in the sun before sale at 30% to 35% moisture content.

Milling

The final steps in coffee processing involve removing the last layers of dry skin and remaining fruit residue from the now dry coffee, and cleaning and sorting it. These steps are often called dry milling to distinguish them from the steps that take place before drying, which collectively are called wet milling.

Hulling

The first step in dry milling is the removal of what is left of the fruit from the bean, whether it is the crumbly parchment skin of wet-processed coffee,the parchment skin and dried mucilage of semi-dry-processed coffee, or the entire dry, leathery fruit covering of the dry-processed coffee. Semi-dry hulling at 30% to 35% moisture ( Giling Basah), as occurs in Indonesia, is thought to reduce acidity and increase body. Hulling is done with the help of machines, which can range from simple millstones to sophisticated machines that gently whack at the coffee.

Polishing

This is an optional process in which any silver skin that remains on the beans after hulling is removed in a polishing machine. This is done to improve the appearance of green coffee beans and eliminate a byproduct of roasting called chaff. It is described by some to be detrimental to the taste by raising the temperature of the bean through friction which changes the chemical makeup of the bean.

Cleaning and sorting

Sorting by Size and Density: Most fine coffee goes through a battery of machines that sort the coffee by density of bean and by bean size, all the while removing sticks, rocks, nails, and miscellaneous debris that may have become mixed with the coffee during drying. First machines blow the beans into the air; those that fall into bins closest to the air source are heaviest and biggest; the lightest (and likely defective) beans plus chaff are blown in the farthest bin. Other machines shake the beans through a series of sieves, sorting them by size. Finally, a machine called a gravity separator shakes the sized beans on a tilted table, so that the heaviest, densest and best vibrate to one side of the pulsating table, and the lightest to the other.

Sorting by Color: The final step in the cleaning and sorting procedure is called color sorting, or separating defective beans from sound beans on the basis of color rather than density or size. Color sorting is the trickiest and perhaps most important of all the steps in sorting and cleaning. With most high-quality coffees color sorting is done in the simplest possible way: by hand. Teams of workers pick discolored and other defective beans from the sounds beans. The very best coffees may be hand-cleaned twice (double picked) or even three times (triple picked). Coffee that has been cleaned by hand is usually called European preparation; most specialty coffees have been cleaned and sorted in this way.

Color sorting can also be done by machines. Streams of beans fall rapidly, one at a time, past sensors that are set according to parameters that identify defective beans by value (dark to light) or by color. A tiny, decisive puff of compressed air pops each defective bean out of the stream of sound beans the instant the machine detects an anomaly. However, these machines are currently not used widely in the coffee industry for two reasons. First, the capital investment to install these delicate machines and the technical support to maintain them is daunting. Second, sorting coffee by hand supplies much-needed work for the small rural communities that often cluster around coffee mills. Nevertheless, computerized color sorters are essential to coffee industries in regions with relatively high standards of living and high wage demands.

 Grading

Grading is the process of categorizing coffee beans on the basis of various criteria such as size of the bean, where and at what altitude it was grown, how it was prepared and picked, and how good it tastes, or its cup quality. Coffees also may be graded by the number of imperfections (defective and broken beans, pebbles, sticks, etc.) per sample. For the finest coffees, origin of the beans (farm or estate, region, cooperative) is especially important. Growers of premium estate or cooperative coffees may impose a level of quality control that goes well beyond conventionally defined grading criteria, because they want their coffee to command the higher price that goes with recognition and consistent quality.

Other steps

 Aging

All coffee, when it was introduced in Europe, came from the port of Mocha in what is now modern day Yemen. To import the beans to Europe the coffee was on boats for a long sea voyage around the Horn of Africa. This long journey and the exposure to the sea air changed the coffee's flavor. Later, coffee spread to India and Indonesia but still required a long sea voyage. Once the Suez Canal was opened the travel time to Europe was greatly reduced and coffee whose flavor had not changed due to a long sea voyage began arriving. To some degree, this fresher coffee was rejected because Europeans had developed a taste for the changes that were brought on by the long sea voyage.To meet this desire, some coffee was aged in large open-sided warehouses at port for six or more months in an attempt to simulate the effects of a long sea voyage before it was shipped to Europe.

Although it is still widely debated, certain types of green coffee are believed to improve with age; especially those that are valued for their low acidity, such as coffees from Indonesia or India. Several of these coffee producers sell coffee beans that have been aged for as long as 3 years, with some as long as 8 years. However, most coffee experts agree that a green coffee peaks in flavor and freshness within one year of harvest, because over-aged coffee beans will lose much of their essential oil content.

Decaffeination

Decaffeination is the process of extracting caffeine from green coffee beans prior to roasting. The most common decaffeination process used in the United States is supercritical carbon dioxide (CO₂) extraction. In this process, moistened green coffee beans are contacted with large quantities of supercritical CO₂ (CO₂ maintained at a pressure of about 4,000 pounds force per square inch (28 MPa) and temperatures between 90 and 100 °C (194 and 212 °F)), which removes about 97% of the caffeine from the beans. The caffeine is then recovered from the CO₂, typically using an activated carbon adsorption system.

Another commonly used method is solvent extraction, typically using oil (extracted from roasted coffee) or ethyl acetate as a solvent. In this process, solvent is added to moistened green coffee beans to extract most of the caffeine from the beans. After the beans are removed from the solvent, they are steam-stripped to remove any residual solvent. The caffeine is then recovered from the solvent, and the solvent is re-used. Water extraction is also used for decaffeination. Decaffeinated coffee beans have a residual caffeine content of about 0.1% on a dry basis. Not all facilities have decaffeination operations, and decaffeinated green coffee beans are purchased by many facilities that produce decaffeinated coffee.

Storage

Green coffee is fairly stable (approx. up to 1 year) if stored correctly. Most often it is in a Jute sack kept in a cool, clean, and dry place.

Roasting

Although not considered part of the processing pipeline proper, nearly all coffee sold to consumers throughout the world is sold as roasted coffee. Consumers can also elect to buy unroasted coffee to be roasted at home.