Home roasting is the process of roasting coffee from green coffee beans on a small scale for personal consumption. Home roasting of coffee has been practiced for centuries, and has utilized numerous methods of roasting the beans such as roasting in pans over a fire and hand turning iron drums on a stovetop.[1]
Until World War I it was more common to roast coffee at home than to buy pre-roasted coffee. During the latter part of the 20th century, commercial coffee roasting became prevalent, combined with the distribution of instant coffee, home roasting decreased substantially.[1]
In recent years there has been a revival in home roasting; what was originally a necessity has now become a hobby.[2] The attractions are four-fold: enjoying fresh, flavorful coffee; experimenting with various beans and roasting methods; perfecting the roasting process; and saving money.
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Enjoying coffee made from freshly roasted beans is one of the major driving factors in home roasting. The rule of thumb for coffee freshness is that green (unroasted) coffee beans will keep for two years, roasted beans for two weeks, and ground coffee for two hours. Home roasting has the advantage of being able to roast smaller volumes of coffee to match consumption so that the roasted coffee is used before it goes stale. Depending on the origin and method of storage, coffee flavor peaks from 24 hours to 7 days after roasting.[3]
Subsequently, flavor declines at a rate which depends on origin and storage method. The flavor of ground coffee deteriorates even faster. Many factors cause the decline of flavor after roasting, including the oxidation of oils and other compounds exposed to atmospheric oxygen after roasting damages bean cell wall integrity, and the evaporation of flavor-active volatile compounds. Roasting coffee beans produces a significant amount of carbon dioxide (CO2) gas; this CO2 preserves freshness to the extent that it excludes atmospheric oxygen. Other means of extending freshness include refrigeration, freezing, vacuum packaging, and displacing oxygen in ambient air with an inert gas.
Home roasters have access to a wide selection of green coffee beans, and is one of the attractions to the hobby. Home roasters can purchase small quantities of high quality beans from numerous importers and distributors. Some of the beans are rare or award winning, while others are from coffee orchards known for their quality and unique flavor. It is common for home roasters to purchase beans that come from a country, region, and orchard, and harvest year.
Those who are roasting for economic reasons can purchase green beans in bulk at lower cost than roasted beans from retailers. Home roasters can chose various types of equipment, each of which has certain attributes that can alter the flavor.
A roasting profile describes the time the beans spend at each temperature during roasting including the final temperature prior to cooling. This greatly affects the flavor, aroma, and body of the coffee. Home roasters go to great lengths to control these roasting parameters including using computers for process control and data logging. Manually controlled equipment makes precise and repeatable profile control more difficult, though an experienced roaster can produce very good results.[4] One of the lures of the hobby is experimenting with the roasting profile to produce optimal tasting coffee, albeit subjective.
Coffee roasting produces chaff and smoke, and should be done in a well-ventilated area, which is often difficult to accomplish in a home environment. Coffee roasting outdoors is affected by changes in air temperature and wind speed, requiring more frequent adjustments to the roasting process to produce repeatable results.
Depending on the type of beans chosen, roasters can save from 25–50% per pound by roasting at home.[5]
A simple technique for roasting green coffee beans is to stir them in a skillet or wok over high heat. Coffee can be roasted in the oven provided that they are put only one bean deep in a perforated baking tray. These methods produce coffee beans with a variety of roast levels as it is almost impossible to achieve a consistent roast merely by stirring, however, some people like the resultant melange roast.[6]
This lack of control on stove top roasting has lead some home roasters to innovative adaptation of equipment intended for other purposes and fabricating custom equipment. Heat guns (normally used for stripping paint) aimed into metal bowls, home-made steel drums suspended and rotated over outdoor gas grill burners, and modified hot-air popcorn poppers are examples of coffee roasters made from readily available parts. Heat guns and modified hot-air popcorn poppers are the least expensive home roasting equipment. Home bread-making appliances can be modified to roast coffee, too.
There are an increasing number of consumer coffee roasters. They automate the roasting process and avoid the hazards of using equipment not designed for high temperature operation. The main drawbacks with many of the dedicated home roasting appliances are their small 75-to-300-gram (2.6 to 11 oz) capacity, limited roasting control, and often slow cooling abilities.
Some home roasters design and build roasting equipment from scratch making full-sized sample roasters, diminutive commercial-style coffee roasters, or inventing new roasting machines. Others use off-the-shelf materials, found objects, and simpler construction methods. Such machines typically have greater capacity or roasting control than home roasting appliances.
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