Coffee roasting
Italian roasted coffee beans Roasting coffee transforms the chemical and physical properties of green of green coffee beans into roasted coffee coffee products. products. The roasting process is integral to producing a savory cup of coffee. When roasted, the green coffee bean expands to nearly double its original size, changing in color, taste, smell and density. Unroasted beans boast all of coffee’s acids, protein, and caffeine — but none of its taste. It takes heat to spark the chemical reactions that turn carbohydrates and fats into aromatic oils, burn off moisture and carbon dioxide, and alternately break down and build up acids, unlocking the characteristic coffee flavor.
As green coffee is more stable than roasted, the roasting process tends to take place close to where it will be consumed. This reduces the time that roasted coffee spends in distribution, helping to maximise its shelf life. The vast majority of coffee is roasted commercially on a large scale, but some coffee drinkers roast coffee themselves in order to have more control over the freshness and roast level of the beans.
[edit edit]] Process The coffee roasting process consists essentially of cleaning, roasting, cooling, grinding, and packaging operations. In larger operations, bags of green coffee beans are hand or machine-opened, dumped into a hopper , and screened to remove debris. The green beans are then weighed and transferred by belt or pneumatic conveyor to storage hopp ers. From the storage hoppers, the green beans are conveyed to the roaster. Roasters typically operate at temperatures between 370 and 540 °F (188 and 282 °C °C), ), and the beans are roasted for a period of time ranging from a few minutes to about 30 minutes. Roasters are typically horizontal rotating drums that are heated from below and tumble the green coffee beans in a current of hot gases. The heat source can be supplied by natural gas,
Liquefied petroleum gas (LPG), electricity or even wood. These roasters can operate in either batch or continuous modes and can be indirect- or direct-fired. An alternate to the drum coffee roaster was roaster was developed by Michael Sivetz for which he was given US patent 3,964,175 on June 22, 1976. It involves roasting the coffee beans while they are levitated on a cushion of heated air. The process is called a fluidized bed and is commonly used in other food processing applications. profile, when bringing Many people who roast coffee prefer to follow a "recipe", or roast or roast profile, out the flavour characteristics they wish to highlight. Any number of factors may help a person determine the best profile to use, such as the coffee's origin, varietal, processing method or desired flavour characteristics. A roast profile can be presented as a graph showing time on one axis and temperature on the other, which can be recorded manually or using computer software and data loggers linked to temperature probes inside various parts of the roaster. Indirect-fired roasters are roasters in which the burner flame does not contact the coffee beans, although the combustion gases from the burner do contact the beans. Direct-fired roasters contact the beans with the burner flame and the combustion gases. At the end of the roasting cycle, water sprays are used to "q uench" the beans. Following roasting, the beans are cooled and run through a "destoner". Destoners are air classifiers that remove stones, metal fragments, and other waste not removed during initial screening from the beans. The destoners pneumatically convey the beans to a hopper, where the beans are stabilized and dried. This stabilization process is called equilibration. Following equilibration, the roasted beans are either ground or packaged as whole beans. Roasted whole beans can be considered fresh for up to, but not exceeding one month. Once coffee is ground it is best used within 24 hours.
[edit edit]] Packaging Extending the useful life of roasted coffee relies on maintaining an optimum environment for the beans. The first large scale preservation technique was vacuum packing. However, because coffee emits CO2 after roasting, coffee to be vacuum packed must be allowed to de-gas for several days before it is sealed. To allow more immediate packaging, pressurized canisters or foil-lined bags with pressure-relief valves can be used.
[edit edit]] Darkness As the bean absorbs heat, the color shifts to yellow and then to a light "cinnamon" brown then to a dark brown. During roasting, oils appear on the surface of the bean, making it shiny. The roast will continue to darken until it is removed from the heat source. At lighter roasts, the bean will exhibit more of its "origin flavor" - the flavors created in the bean by the soil and weather conditions in the location where it was grown. Coffee beans from famous regions like Java Java,, Kenya Kenya,, Hawaiian Kona, Kona, and Jamaican Blue
Mountain are usually roasted lightly so their signature characteristics dominate the flavor. [1] As the beans darken to a deep brown, the origin flavors of the bean are eclipsed by the flavors created by the roasting process itself. At darker roasts, the "roast flavor" is so dominant that it can be difficult to distinguish the origin of the beans used in the roast. These roasts are sold by the degree of roast, ranging from "Light Cinnamon Roast" through "Vienna Roast" to "French Roast" and beyond. A note on flavor: Describing the tastes of different roasts is as subjective as putting a wine into words. In both cases there’s no substitute for your own personal taste. As a guide, if you can see the oil on the beans as in the image above, you are more likely to taste the roasting flavours, than the individual characteristics of the beans.
Roast level
Light
Medium
Notes
After about seven minutes the beans “pop” and double in Cinnamon size, and light roasting is roast, half city, achieved. American mass New England market roasters typically stop here.
Full city, American, regular, breakfast, brown
At nine to eleven minutes the beans reach this roast, which U.S. specialty sellers tend to prefer.
Surface
Flavor
Dry
Light-bodied and somewhat sour, grassy, and snappy
Dry
A bit sweeter than light roast; full body balanced by acid snap, aroma, and complexity
After 12 to 13 minutes the Somewhat spicy; High, Viennese, beans begin hissing and complexity is traded Italian popping again, and oils rise to Slightly for rich chocolaty Dark Espresso, the surface. Roasters from the shiny body, aroma is Continental U.S. Northwest generally exchanged for remove the beans at this point. sweetness
Darkest
French
After 14 minutes or so the Smokey; tastes beans grow quiet and begin to primarily of smoke. Having caramelized, Very oily roasting, not of the the bean sugars begin to inherent flavor of the carbonize. bean
Grades of coffee roasting; from left: unroasted (or "green"), light, cinnamon, medium, high, city, full city, Italian, and French.
[edit edit]] Home roasting Main article: Home article: Home roasting coffee Home roasting is the process of roasting small batches of green coffee beans for personal consumption. Roasting coffee in the home is something that has been practiced for centuries, and has included methods such as heating over fire coals, roasting in cast iron pans, and rotating iron drums over a fire or coal bed. Computerized drum roasters are available which simplify home roasting and some home roasters simply roast in an oven or in air popcorn poppers.
Up until the 20th century, it was more common for at-home coffee drinkers to roast their coffee in their residence than it was to buy roasted coffee. During the 20th century, home roasting faded in popularity with the rise of the commercial coffee roasting companies. In recent years home roasting of coffee has seen a revival. In some cases there is an economic advantage, but bu t primarily it is a means to achieve finer control o ver the quality and characteristics of the finished product.
[edit edit]] Emissions and control This section does not cite any references or sources. sources. Please help improve this section by section by adding citations to reliable sources. sources. Unverifiable material may be challenged and removed. (February 2008)
Particulate matter (PM), matter (PM), volatile organic compounds (VOC), organic acids, acids, and combustion products are the principal emissions from coffee processing. Several operations are sources of PM emissions, including the cleaning and destoning equipment, roaster, cooler, and instant coffee drying equipment. The roaster is the main source of gaseous pollutants gaseous pollutants,, including alcohols alcohols,, aldehydes aldehydes,, organic acids, acids, and nitrogen and sulfur compounds. Because roasters are typically natural gas-fired, carbon monoxide (CO) and carbon dioxide (CO2) emissions result from fuel combustion. Decaffeination and instant coffee extraction and drying operations may also be sources of small amounts of VOC. Emissions from the grinding and packaging operations typically are not vented to the atmosphere. Particulate matter emissions from the receiving, storage, cleaning, roasting, cooling, andstoning operations are typically ducted to cyclones before being emitted to the
atmosphere. Gaseous emissions from roasting operations are typically ducted to a thermal oxidiser or thermal catalytic oxidiser following PM removal by a cyclone. Some facilities use the burners that heat the roaster as thermal oxidisers. However, separate thermal oxidisers are more efficient because the desired op erating temperature is typically between 650°C and 816°C 81 6°C (1200°F and 1500°F), which is 93°C to 260°C (200°F to 500°F) more than the maximum temperature of most roasters. Some facilities use thermal catalytic oxidizers, which require lower operating temperatures to achieve control efficiencies that are equivalent to standard thermal oxidisers. Catalysts are also used to improve the control efficiency of systems in which the roaster exhau st is ducted to the burners that heat the roaster. Emissions from spray dryers are typically controlled by a cyclone followed by a wet scrubber .
[edit edit]] Gallery
Unroasted coffee beans at various stages L–R: one year Unroasted coffee after drying, after drying, Roasted coffee beans at later stages. An old largefresh picked. capacity coffee beans The beans are 7 and 8 roaster made years old. from cast iron.
An example of lighter roasted, versus darker roasted beans. The degree of roasting which is ideal for coffee in general, and a given varietal or blend is highly subjective.
