The quality of coffee or caste vary by each plant, each county and different growing areas. Robusta coffee is rated lower than arabica due to lower quality and price which is cheaper. The most expensive coffee in the world's rarest and Kopi Luwak name (or "weasel coffee") of Indonesia and Vietnam. This is not a coffee like that in a coffee processing using the digestion of mongoose. Price per weight of coffee is around 20 million VND (1300 USD) and annual only 200 kg were sold on the world market.
Unlike other beverages, coffee's main function is not refreshing, even though the American people to drink it as refreshments. Many people drink it with the aim of creating excitement. According to a study published in August 2005 by the American chemist Joe Vinson of the University of Scranton, the coffee is an important source of supply of antioxidants (antioxidant) for the body, as previously they are only found in fruits and vegetables. These substances also indirectly reduce the risk of cancer in humans.