Home Roasting Coffee
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Home roasting refers to the process of buying green coffee beans and roasting them in your own home. 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. 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 pre-roasted coffee. During the 20th century, roasting coffee in the home faded in popularity with the rise of the professional coffee roasting companies (source: Uncommon Grounds, Mark Pendergrast, 2000).

In modern times home roasting of coffee has seen a revival, and while often done for purely economic reasons, increasingly it has become a tool and a hobby for the coffee aficionado to get access to better quality, fresher roasted beans.

Freshness

Roasted coffee outgasses after the roasting process with peak flavour typically occurring within 24-48 hours. Within a week the beans become progressively staler with much of the flavour complexity lost. Ground coffee becomes stale in a matter of hours.

Consider then the vacuum packed packets of coffee available in a normal supermarket. Since roasted coffee outgasses after roasting, the whole or ground beans have been left exposed to air for sufficient time for the outgassing to cease resulting in the coffee being stale before it is packed.

In contrast, green beans can have a shelf life of one year or longer before any noticeable degradation in quality occurs. Some specialty beans are deliberately aged to bring out desirable taste attributes and in the case of monsooned coffee beans, left semi-exposed to the weather. You would not be mistaken in thinking that there are many similarities between coffee beans and wine with both being heavily influenced by their respective environments. Soil, weather, farming techniques, etc. have dramatic effects on the flavour characteristics of both wine and coffee.

Quality

When compared to buying generic roasted beans, home roasting provides a wealth of control over the the origin of the beans and the roasting method. Large commercial roasters are typically far more interested in reducing their costs than increasing quality so they will often source the cheapest beans rather than the best beans, although some specialty commercial roasters offer a more artisan approach to their bean choices. Home roasters have access to specialty suppliers who source not only the best types of beans but will often seek out the best lots of beans from an individual plantation. These beans generally cost considerably more than the cheapest beans but will have assured favourable characteristics sought by coffee connoisseurs.

Quality in home roasted coffee is often associated with the source of green beans used and the freshness factor, but not always with the equipment that has been used in the past. Limited ability to control a roasting profile, along with very fast roasting times on some devices can often lead to limited flavor profiles in a green coffee that professional roasting machines can expose and develop to their fullest. Further, slow cooling can dull or flatten the flavor profile of a coffee.

Developments in the machines built for roasting coffee in the home are addressing these drawbacks, and recently, the home coffee roaster has had better access to more sophisticated home roasting equipment to not only overcome these drawbacks, but provide unheard of control over the roasting process. See Equipment for further information on these technology developments.

Cost

See Equipment below for a discussion on equipment costs.

One caveat when comparing cost is that green beans have a higher moisture content than roasted beans with a 15-18% loss in weight depending on roast duration so the actual cost saving is proportionally less. The cost of green beans varies from one supplier to another and will also vary by type, and relative scarcity of the bean based on the size of the crop. You can expect to pay somewhere between a quarter and a third of the cost of the same quantity of run of the mill roasted beans, although the cost can be almost as high as the equivalent roasted beans from some suppliers due to the limited market for green beans and loss of markup by the supplier. Home roasters easily trade off the cost against the improvement in quality of the beans.

Equipment

Home roasting is how all coffee roasting started with manual agitation of beans over an open flame. As recently as 50 years ago it was common place for a family to roast beans for their own consumption. With the ongoing desire to reduce manual effort in the home, commercial suppliers now dominate the roasted coffee market and sales of freeze dried coffee far outweighs fresh bean consumption.

These days home roasters have a variety of equipment available that is either specifically made for home roasting or can be reused for the purpose. The most commonly used DIY options are popcorn poppers (both electric and manual stovetop), heat/hot air guns (normally for stripping paint), and barbeque roasting with home made steel drums suspended and rotated over burners.

There are a variety of consumer appliances made specifically for coffee roasting such as the Hearthware iRoast2, Swissmar Alpenrost, Zach & Dani's Home Roaster, the FreshRoast +8, HOTTOP Bean Roaster, and the Gene Cafe Roaster. These are generally more expensive than DIY options but offer far more automation of the process and avoid the potential hazards of reappropriating other equipment which may be pushed outside of its intended operating range by this unexpected use.

Most of the purpose-built homeroasting appliances are either "air" or "drum" roasters. Commonly, it is held that fluid-bed or air roasting method tends to produce more acidity in the coffee beans while the drum roasting method tends to produce more body in the coffee beans. More recent exploration into the art of roasting in the home has shown that the fast heat up times typical in many fluid bed roasters leads to greater acidity being exposed in the bean, whereas the slower heat up times in drum roasters help develop more body. As new machines come to market that allow for greater control over the heat application process (also known as a "profile" in the roasting profession), it should be possible for fluid bed air roasters to develop more body and less acidity, and vice versa for the drum roaster appliances.

Recently, there have been "hybrid" roasters introduced to market that borrow technologies and methodologies being explored in the professional roasting field; most notably the Gene Cafe roaster out of Korea. Recently introduced into North America, this roaster uses an oscilating, off-axis drum rotation to agitate and apply even roasting to the beans, and uses a sealed hot air flow to heat the roast drum chamber.

The main drawbacks with many home roasting appliances are their relatively small batch size, with some roasters capable of handling only 75 grams of green coffee (others can handle up to 300 grams); frequent limitations in what is called a "roasting profile" often used by professional roasters to further control and/or "sculpt" the resulting coffee roast; and often slow cool down abilities for the freshly roasted beans, which could result in a dulling or flattening of potential flavors in the coffee.

New devices coming to market are providing more control over some of these variables, including the iRoast2 which allows for programmable roasting profiles, and the Gene Cafe Roaster which allows the user to adjust both roast time and temperature at any time during the roast. The HOTTOP is notable as having one of the best cooling cycles of any purpose-built home roasting appliance, coming close to the ability of small professional roasters.

These improvements, along with other developments are fostering a better understanding and appreciation for the art of roasting coffee. They are also continually improving the quality of coffee roasted in the home. Home roasting allows the coffee aficionado to be integral in the process and become more knowledgeable while enjoying better, cheaper and fresher coffee.

Coffee beans can be roasted to different levels and is usually dependent on the variety of coffee bean being roasted as well as the style of coffee being prepared. A typical roast takes around twenty minutes to complete.

An example of a fairly automated machine can be seen in the images here showing the stages of roasting with the HOTTOP drum roaster.

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It uses material from Wikipedia.