Course:FNH200/2012w Team02 Coffee

Delicious steaming coffee

Coffee, a drink brewed from roasted beans from the Coffea Plant, is one of the most popular beverages in the world. According to 2010 Canadian coffee drinking study, around 65% of Canadian adults consume coffee and drink an average of 2.8 cups of coffee every day. Therefore, some claim that coffee is the most widely consumed liquid in the world aside from water. Coffee is something more than a just beverage; while people love coffee because it has appealing smells and tastes, it is also enjoyed for its unique stimulating properties. The major chemicals in coffee are caffeine and caffeol, and it is these two factors that play important role in coffee's goodness. Caffeine is the principal stimulant found in coffee, and it increases the capacity for muscular and mental work, whereas caffeol, also known as coffee oil, supplies the wonderful flavor and the aroma of coffee. Unlike sodas and other popular beverages, making coffee is a very labor intensive process. A cup of good coffee stems from the hard-work of coffee planting, harvesting, coffee bean processing, chopping, and various manufacturing processes. The process of preparing coffee after all the processing takes fair time as well, but can now be circumvented with the invention of instant coffee. Although many people drink coffee, these complicated but interesting manufacturing processes are not widely known. Here we will introduce the processes in the making of a cup of coffee.

Coffee harvesting

Locations of cultivations of r:Coffea robusta, m:Coffea robusta and Coffea arabica, a:Coffea arabica

Planting

Coffee beans are the seeds from Coffea trees. The two dominant varieties of the Coffea plant which are cultivated are Coffea Arabic and Coffea Robusta. These trees are typically planted in large quantities in shaded areas initially. As the growing process continues, exposure to sunlight is increased gradually and shading is completely removed during the last two months prior to planting coffee seedlings. The necessity for sunlight is the reason why coffee is primarily cultivated in countries close to the equator, allowing for sun exposure for the crops.Plants must grow until moist conditions and as a result, they are planted during the wet season and are watered often.

Harvesting

Workers selectively harvesting coffee

Coffee plants generally take 3 to 4 years to bear fruit. The fruit is called the coffee cherry and can be picked when they turn bright red. Since the coffee plants are not usually planted on flat ground, harvesting is mainly done by hand by workers. There are two ways to harvest the fruit:

Strip picked

This method is more efficient as the entire crop is gathered at the same time either by hand or by the use of a machine. Unfortunately this also means that there is a large quantity of fruit that remains unripe.

Selectively picked

This process is more labour-intensive but results in better quality and higher quantity of ripe fruit. Workers walk around the field picking ripe cherries by hand, being careful to pick the cherries when they are just ripe. As this process requires many workers, even though they alternate between trees every 8-10 days during harvest season, it is very costly. As a result, selectively picked crops are mainly reserved for finer Arabica beans.

For most coffee producing countries, there is only one main harvest in the year. Others have 2 periods where flowers bloom on the plants and therefore, there is a main and secondary crop.

Processing

Coffee beans are the seeds of the cherry fruit. In processing, the beans need to be removed and the moisture must be removed because they can be roasted. There are two ways that this can be accomplished.

Dry method

The dry method has been used for a long time and is simple as it does not employ the use of fancy equipment. The cherries that have been recently picked are sorted to ensure that only the crops that are at the perfect ripeness are used. Ideal cherries are then laid out in the sun to dry. As a precaution, the fruits are raked and moved around to avoid spoiling. The length of the treatment varies depending on the humidity and weather conditions. Once cherries reach a moisture level of 11%, they are moved into storage to await further processing.

Wet method

The wet method requires more resources to accomplish, but produces better quality coffee beans. As a result, the products of this method can sell for higher prices. Similar to the dry method, collected cherries are sorted and cleaned prior to processing. The pulp of the fruit is separated from the seed by means of machine that forces the flesh and skin to remain on one side and the beans on the other. Beans flow into water channels so the heavier, ripe cherries sink to the bottom and the unripe fruits float on top. The seeds move to large containers where they undergo fermentation which continues for 12-48 hours depending on the conditions of the beans. This step of the process is done to remove the thin layer of mucilage that is attached to the bean through enzyme degradation. When fermentation is complete, the beans take on a rough texture as the slimy layer of mucilage is removed. Beans are then rinsed with water and dried. The products of this method are known as parchment coffee or wet-processed coffee.

Roasting

The roasting process turns green coffee into the end prodcut (brown coffee beans) we see in stores. Roasting machines that contain the beans heat up to a temperature of 550²F. The beans are constantly moving to keep from burning and are heated until they reach an internal temperature of 400²F. The change of colour from green to brown is due to caramalization, and the trademarked bitter flavour and aromas are created as sucrose degrades while caffeol is released during heating. These two processes occurring in conjunction is coined as pyrolysis (breaking down in heat). Usually roasting is done in the countries in which the coffee beans are sold in as roasted beans must be consumed and used as soon as possible.

An overview of how coffee is harvested and processed

Manufacturing Processes

Coffee beans are ground in a process known as milling before it can undergo brewing. Methods of brewing that expose the coffee grounds to heated water for longer periods of time would require grinds that are more coarse and vice versa for faster brewing methods. The pairing of two is important because the use of a very fine grind in a brewing process that exposes the grind to an extended period will produce a harsh and bitter taste. On the other hand, the use of a very coarse grind with a short brewing period will lead to a watery diluted taste. It is important that the grind is uniform so that one brewing method can accommodate the grind. Coffee can be ground by 4 different methods: burr-grinding, chopping, pounding, and roller grinding.

Burr Grinding

Traditional burr grinder

Burr-grinding uses two revolving abrasive surfaces. There is usually a revolving screw that is rotated to push the food through the mill. The screw may be powered electrically or manually. It is important to note that burr mills do not have any rotating blades like those of conventional grinders. As a result, they do not heat the product due to friction. This keeps the aroma and flavor in of the coffee beans in. Burr mills often lead to uniform sized particles. An example of a commonly used bur mills would be pepper and salt mills. The particle size can be adjusted by changing the distance between the two abrasive surfaces, depending on whether or not a coarse or finer grind is preferred. Traditionally, burr-mills were manually powered by hand, by rubbing one surface against the other. However, they have been mostly replaced by electrically powered ones . Conical burr grinders utilize steel abrasive surfaces that allow an effective grind while maintaining less than 500 reps per minute. This allows for minimum frictional heating allowing the aroma of the blend to remain intact. Disk type burrs rotate faster and produce more friction, but are cheaper and can work well for small quantities of coffee since it doesn’t allow time for heat to build up.

Chopping

Blade grinder

Chopping is the use of a traditional blade grinder that is rotated at 20,000 to 30,000 reps per minute. The use of this method is usually cheaper than burr grinders but the blend will not be as uniform and will cause many different sizes to be present. This means that finding an appropriate brewing method for the grind will be difficult due to the inconsistency. In addition, the blend will also be warmed by friction so that the aroma and flavor of the coffee is not as strong as burr grinding

Pounding

Mortar and pestle used for pounding coffee beans

Pounding is the grinding technique that is popular in Arabic or Turkish coffee. It can be carried out in a mortar and pestle and the coffee beans are pounded until they are very fine, more so than the two methods above. Coffee grinds produced with this method are usually brewed in hot but not boiling water for a short duration of time to ensure optimal flavor. Prolonged brewing of the coffee will result in a burnt or cooked taste that is unfavorable. Roller grinding is when the coffee beans pass through a pair of corrugated rollers. This method produces a more even size grind and heats the coffee up less during the process than the other methods. However, due to the size of machinery and the cost, it is limited to industrial coffee producers .

Roller Grinding

Roller grinding is when the coffee beans pass through a pair of corrugated rollers. This method produces a more even size grind and heats the coffee up less during the process than the other methods. However, due to the size of machinery and the cost, it is limited to industrial coffee producers. .

Decaffeination & Caffeine Health Associations

Decaffeination is the act of removing the caffeine content from coffee beans. In general, the process involves the steaming of unroasted coffee beans. They are then rinsed with a solvent that extracts the caffeine but leaves all the other chemicals that make up the overall flavor of the coffee intact. The whole process can be repeated 8-12 times until the international standard of 97% of the caffeine removed is reached. There are 7 major methods of decaffeination: Roselius process, Swiss water process, direct method, indirect method, and CO2 method .

Caffeine is a metabolic stimulant, it causes improved wakefulness, focus, and clearer thought flows. It may improve performance while under sleep deprivation but can consequently cause insomnia. At low to moderate doses, caffeine provides mostly positive effects . However, in higher doses, it can cause caffeinism. Symptoms include nervousness, irritability, restlessness and headaches .

Roselius Process

The Roselius process was the first commercially successful method. It involves the use of steaming the coffee beans with a combination of acids and bases followed by the use of benzene as a solvent to remove the caffeine. However, due to safety concerns with benzene use, it is no longer used .

Swiss Water Process

The Swiss water process is currently in use by The Swiss Water Decaffeinated Coffee Company in Burnaby, British Columbia. Unroasted coffee beans are be immersed in water so that the caffeine is extracted. This however, also causes desirable oils that make up the flavor of the coffee to be extracted as well. The company deals with this obstacle by saturating the water with the desirable oils and compounds so that the coffee beans still retain their content. The saturated water is known as green coffee extract and is made by taking another batch of unroasted coffee beans and immersing them in water so that their contents are extracted into the water. The beans are then discarded. The extract then has its caffeine filtered out. Another batch of unroasted beans are then immersed in this extract so that only caffeine would leave the beans .

Direct Method

The direct method involves steaming coffee beans for 30 minutes and then rinsing with dichloromethane or ethyl acetate for 10 hours. The solvents are then drained and the beans are steamed again for another 10 hours to ensure that the left over solvents are completely removed .

Indirect Method

The indirect method involves soaking beans in hot water for a few hours. The beans are then removed and dichloromethane or ethyl acetate is added to the solution to extract the caffeine from the water. The water is then cycled through this process with a batch of unroasted coffee beans. Eventually equilibrium is reached where the water and beans end up having a similar composition except for the caffeine .

CO2 Method

The CO2 method involves immersing the unroasted coffee beans in supercritical carbon dioxide in a pressure chamber ranging from 73 to 300 atmospheres. The beans are kept in this chamber for about 10 hours whereby the caffeine is dissolved into the CO2. Afterwards, the CO2 is then removed and the chamber is allowed to return back to atmospheric pressure. The caffeine is removed from the CO2 through charcoal filters and the CO2 can be recycled .

Preparation of Beverage

A French Press for Coffee Steeping

Drip system & Filtration

This method is most commonly used in households and restaurants as it is simple. Ground coffee is placed at the top of a machine. Boiling water is then poured or fed into the machine to soak the coffee grinds and the resulting liquid drips through a filter into a collecting vessel. This is the modern adaptation of simply boiling water and adding ground coffee, which was the method of coffee making up until 1930

Percolator

Grinds are held in a container at the top of a system. Typically, there is a heat generator at the bottom of the pot to heat up the system. A tube is inserted from the bottom and delivers the boiling water to the top of the pot where the water is spread over the grinds. The solution resulting from seeping through the grinds travels down the pot to join the heated water solution at the bottom. This process is repeated many times until the grinds are used up. Since this process saturates the grinds and boiling water passes through constantly, this method tends to produce a bitter tasting brew.

Steeping

Steeping involves the use of a French Press (a narrow filtering tube with a plunger system at the top). Coffee grounds are placed into the filtered cylinder and submerged with boiling water. The coffee grounds are allowed to "steep" for a desired time, and then then plunger is pushed down to force the water out of the cylinder while the filter prevents the grounds from passing through

This method can provide a much stronger and bitter brew as there is more control over the time which water comes in contact with the coffee grinds.

Standard identity, Additives & Nutrition

Under the Food and Drug Act of Canada, coffee is defined to be:

(I) Unroasted: the seeds of Coffee Arabica, Coffee liberica Hiern, or Coffee robusta Chev.

(II) Roasted: seeds of the above plants containing at least 10% fat and no more than 6% ash in mass.

The standard identity of decaffeinated raw coffee allows for no more than 0.1% caffeine content, while decaffeinated instant coffee allows no more than 0.3% caffeine.

This is different than the internationally accepted 3% caffeine content in decaffeinated coffee.

There are no additives under the Canadian Food and Drug Regulations which are added to coffee.

Coffee is not prone to bacterial spoilage but rather loss of flavor from oxidation and is preserved not by additives, but from air-tight packaging or processing into instant coffee. Flavour enhancers are not added until the coffee is brewed, so it is not uncommon for coffee to be the only ingredient listed on the product packaging.

Coffee has no significant nutritional properties. It is enjoyed purely for its aromatic and stimulating aspects.

Instant Coffee

instant coffee in stores

Instant coffee (soluble coffee) is the dehydrated powder or granule residues from the dehydration of the coffee beverage. The convenience of instant coffee is due to the fact that it is a post-extraction product of coffee beans; the beverage has simply been pre-prepared and dehydrated for consumption at a later date. In addition to reduced preparation times, instant coffees boasts longer shelf life than group coffee, and also requires less mass to create an equivalent beverage when compared to ground coffee.

The first commercially marketable instant coffee was created in 1906 by George C. Washington, an English chemist living in Guatemala. Coined as “red E coffee” and produced via spray-dry techniques, Washington’s product was the major instant coffee seller until the Nestle Company took over the instant coffee scene in 1938, spurring instant coffee research (backed by the Brazilian coffee industry as they needed coffee preservation methods for their excess harvests). Better dehydration techniques led to greater sales for instant coffee, and by 1954, one in four cups of coffee consumed in households were prepared from instant coffee products. The breakthrough in manufacturing processes for instant coffee came in 1963, as freeze-drying was introduced. Freeze drying is the prevalent drying technique used in modern day instant coffee production as the flavours and aromas are better preserved than in the products of spray drying. (Reconstituted foods which are preserved by freezing retain their natural tastes more-so than those treated by heat)

Production

The foremost step in the manufacturing of instant coffee is extraction. Likewise to brewing the coffee beverage, extraction in the making of instant coffee is the step where the aromatic and flavourful properties of coffee beans are transferred into water, but simply to a much greater extent than in beverage preparation. To produce a coffee brew which is 15-30% coffee solid by weight, roasted ground coffee is treated with water in a pressurized environment at 140-180°C and then cooled and simmered at 100°C. The high heat treatment at 140-180°C extracts the sugars from the ground coffee, which is responsible for the flavour, while the extended treatment at 100°C extracts the aromatic oils from the coffee. The mix of water and coffee grounds are then passed through a filter, and the remaining liquid is then further concentrated via centrifuge and/or evaporation to meet the 15-30% solid mass by weight. The extraction and concentration processes are the reasons why equals portions of instant coffee, when compare to ground coffee, can produce a much stronger brew, which means reduced expenses in storage and shipping for instant coffee.

(This extraction and filtering treatment are not fully efficient, as aromatic and flavour properties are lost in this process. Aromatic oils and solvents which were lost during treatment are captured and sprayed back into the instant coffee at the end of the manufacturing process to minimize flavour and aroma losses)

The concentrated liquid is then moved into drying apparatuses. Spray driers and freeze driers are the most prominent tools used to remove water content to create instant coffee and their functionalities are outlined below.

Spray Drying

Powdered instant coffee

Pellet shaped instant coffee

In the process of spray drying, the concentrated liquid coffee is passed through an atomizer (a nozzle which disperses the liquid into a mist) and is sprayed down a large drying tower. Air blowers at the bottom of the tower direct air which is heated to 250°C upwards into the falling coffee mist. This instantaneously evaporates the water and the remaining dry coffee powder collects at the bottom of the drying tower. This is the process which creates powdered instant coffee. To create instant coffee pellets, the dry powder is introduced back into the drying tower where it agglutinates with additional coffee mist. Successive drying and rehydration by mist increases the size of the final product until it has reached the desired form. This was the first method used to create instant coffee, but is now seldom used due to the emergence of freeze drying. The extreme heat treatment of spray drying results in the losses of aroma and flavour, a side-effect which is not present during freeze drying.

Freeze Drying

Commercial Freeze Drying Apparatus

Freeze drying is the primary method used in modern day instant coffee production. This process can be split into 3 distinctive steps.

Freezing

The concentrated coffee is placed onto trays which are chilled by brine or various refrigeration fluids. The freezing process is gradual, with the temperature slowly lowered over 90 minutes until it reaches -6 °C. This slow cooling allows for the formation of larger coffee clusters in the frozen coffee, as the water particles will be more favourable orientated in their crystal lattice, and impurities such as the solid coffee will be forced together.

Smashing and sieving

The frozen sheet of coffee is then mechanically smashed into pellet sized pieces. Pieces too large or small are sieved out and recycled in the production process.

Sublimation

The frozen coffee pellets are then placed in a vacuum environment. The decrease in pressure allows for the water in the pellets to move from the solid phase directly into the gas phase. As water did not travel through the liquid phase, the solid content of the coffee will not dissolve and thus retains its pellet like shape. The instant coffee is now ready for packaging and shipment.

Facts & Eccentricities of Coffee

1. Coffee was discovered by a goat: a young goat herder in the 9th century noticed one of his goats was acting strange after consuming a cherry from a coffee plant. He then tried it himself.

2. The most expensive type of coffee processing is known as Kopi Luwak with prices reaching $700 USD / kg. It involves the collection of coffee berries after they have been eaten and excreted by the Asian Palm Civet aka the toddy cat .

3. Colombia is the greatest producer of coffee, producing more than 2,600,000 tonnes a year .

4. Coffee beans are actually seeds that are found inside the cherries of an evergreen bush called the Coffea. The cherry is actually very sweet tasting and tarty.

5. Coffee is the second most traded commodity on earth next to oil.

Coffee Vending machine in Japan

Possible Exam Question

What are some benefits of instant coffee when compared to traditional brewing techniques?

• Instant coffee powder is the dehydrated product of the pre-prepared drink. Therefore, consumers only need to add water to make their desired drink instead of waiting long times for traditional brewing techniques to extract flavour and aroma from coffee grinds.
• Instant coffee powder has a longer shelf life compared to the fresh roasted coffee bean variety due to lowered water activity levels resulting from the dehydration process.
• Instant coffee powder will have a consistent flavour (although it may not be desirable to all consumers) if they are the same type of product.