A coffee bean is a seed of the coffee plant, and is the source for coffee. It is the pit inside the red or purple fruit often referred to as a cherry. Even though they are seeds, they are referred to as 'beans' because of their resemblance to true beans. The fruits - coffee cherries or coffee berries - most commonly contain two stones with their flat sides together. A small percentage of cherries contain a single seed, instead of the usual two. This is called a "peaberry." The peaberry is more unusual occurring only between 10 and 15 per cent of the time, and it's a fairly common (yet scientifically unproven) belief that they have more flavour than 'normal' coffee beans Like Brazil nuts (a seed) and white rice, coffee beans consist mostly of endosperm.
The two most economically important varieties of coffee plant are the Arabica and the Robusta; 75-80% of the coffee produced worldwide is Arabica and 20% is Robusta. Arabica beans consist of 0.8-1.4% caffeine and Robusta beans consist of 1.7-4% caffeine. As coffee is one of the world's most widely consumed beverages, coffee beans are a major cash crop, and an important export product, counting for over 50% of some developing nations' foreign exchange earnings.
The coffee tree averages from 5–10 m (16–33 ft) in height. As the tree gets older, it branches less and less and bears more leaves and fruit.
Coffee plants are grown in rows several feet apart. Some farmers plant fruit trees around them or plant the coffee on the sides of hills, because they need specific conditions to flourish. Ideally, Arabica coffee beans are grown at temperatures between 15–24 °C (59–75 °F) and Robusta at 24–30 °C (75–86 °F) and receive between 15–30 cm (5.9–11.8 in) of rainfall per year. Heavy rain is needed in the beginning of the season when the fruit is developing, and less later in the season as it ripens.
When the fruit is ripe, it is almost always handpicked, using either "selective picking", where only the ripe fruit is removed, or "strip-picking", where all of the fruit is removed from a branch all at once. This also gives the growers reason to give their blend of origin a certain Spec called OCR (operation Cherry red). In rare circumstances, the Asian Palm Civet will eat a coffee berry and excrete the beans. These beans are called Kopi Luwak, and can be processed further into a rare and expensive coffee.
There are two methods of processing the coffee berries. The first method is "wet processing", which is usually carried out in Central America and areas of Africa. The flesh of the berries is separated from the seeds and then the seeds are fermented – soaked in water for about two days. This dissolves any pulp or sticky residue that may still be attached to the seeds.
The "dry processing" method is cheaper and simpler, used for lower quality beans in Brazil and much of Africa. Twigs and other foreign objects are separated from the berries and the fruit is then spread out in the sun on concrete or brick for 2–3 weeks, turned regularly for even drying.
The term “green coffee bean” refers to unroasted mature or immature coffee beans. These have been processed by wet or dry methods for removing the outer pulp and mucilage, and have an intact wax layer on the outer surface. When immature, they are green. When mature, they have a brown to yellow or reddish color, and typically weigh 300 to 330 mg per dried coffee bean. Nonvolatile and volatile compounds in green coffee beans, such as caffeine, deter many insects and animals from eating them. Further, both nonvolatile and volatile compounds contribute to the flavor of the coffee bean when it is roasted. Nonvolatile nitrogenous compounds (including alkaloids, trigonelline, proteins and free amino acids) and carbohydrates are of major importance in producing the full aroma of roasted coffee, and for its biological action. Since the mid 2000s green coffee extract has been sold as a nutritional supplement, and has been clinically studied for its chlorogenic acid content and for its lipolytic and weight-loss properties.