Coffee was first roasted in the late 14th century. The earliest method was by roasting the green coffee in a heavy pan over charcoal fire (some hard-core cowboys still roast this way). Late last century, a new process was introduced where beans were spun in a hot air chamber heated by natural gas; this system is still the most widely used to date. With the birth of the computer technology has evolved and when coupled with light heating (as with Halogen) temperatures can now be maintained within +/- 1ºC.
The chemical make-up of the coffee bean changes during the roasting process: water dissipates in the bean and a series of chemical reactions change sugars and starches into oils, which give coffee much of its aroma and flavor. When roasted the coffee bean doubles in size and the caramelization of the sugar turns it from green to brown.
The color and appearance of the roasted bean depends on how long it has been roasted for. The longer it is roasted, the darker the roast. Coffee is usually roasted for about 10 to 20 minutes at temperatures ranging from 400ºF to 425ºF (204ºC to 218ºC).
The secret to developing the aroma and flavor of coffee is found in the roasting of the coffee beans. The length of time, as well as temperature of the roast, are crucial in producing a quality cup of coffee, as well as determining which characteristics will be emphasized or muted. If roasting is too short, the oils won't be brought to the surface and the coffee will have a nutty flavor and lack consistency.
Dark roasted beans contain less acid, have slightly less caffeine than lighter roasted beans and have a shorter shelf life, due to the amount of oils on the surface. In darker roasts, it is the roast's smoky, pungent, burnt taste that dominates overtaking the bean's natural flavor. Many times the dark roast's burnt taste will mask beans that are low in flavor and quality. Contrary to popular belief, a dark roast does not equal a richer, stronger cup. Roasting plays no part in determining the strength of a cup of coffee. It is the amount of water and coffee to be used when brewing that determines the strength.
Lightly roasted coffee beans have a sharper, more acidic taste than darker roasts. The coffee suffers less heat exposure, which maintains the bean's qualities. Because flavor is revealed, light roasts are used with higher quality beans.
Several roasting levels have their own characteristics and may be suitable to different tastes or specific uses; they are the following:
Happy Roasting !!!
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