There are both hot and cold methods of extracting flavour and aroma from ground coffee, and the caffeine content varies with the variety of bean and method of brewing. Generally speaking, one serving (five fluid ounces) of Arabica instant coffee contains about 70 mg of caffeine, while a serving of brewed Robusta may contain 200 mg. In steeping or boiling, pulverized coffee is measured into hot water, which is usually then boiled before being poured off the grounds. In percolation, water is brought to a boil in an urn and fed up a tube to a basket holding the coffee. ...(100 of 2437 words)