Around 850 AD, the story goes, the Ethiopian goat herder Kaldi noticed his goats dancing after eating red cherries. The bean inside is a seed made mostly of endosperm, usually two to a cherry, and in 10 to 15% of cherries a single peaberry, whose premium likely reflects careful sorting more than any proven flavor edge. The word coffee came into English from the Italian caffè around 1600, from Turkish kahve and the Arabic qahwa, which once meant wine and is tied to a root meaning to have no appetite. Coffee grows only in the bean belt between the Tropics of Cancer and Capricorn, and Brazil supplies about 45% of world exports.

The episode follows the seed from harvest to roaster: selective picking versus strip picking, the wet process that ferments sticky mucilage away in water, the dry process that sun dries whole cherries for two to three weeks, and kopi luwak, where a civet’s gut enzymes shorten peptides in the bean. At around 230 degrees Celsius, roasting turns about 85% of trigonelline into vitamin B3, breaks 11S storage proteins into amino acids for the Maillard reaction, and destroys over 70% of chlorogenic acids.

• Arabica grows best at 15 to 24 degrees Celsius with 0.8 to 1.4% caffeine; canephora prefers 24 to 30 degrees with 1.7 to 4.0%.
• Coffee needs 500 to 3,000 millimeters of rain a year, heavy early to trigger flowers and lighter as fruit ripens.
• A dried green bean weighs about 300 to 330 milligrams, roughly half of it structural carbohydrate.
• The diterpenes cafestol and kahweol have protected liver tissue against oxidation in lab experiments.
• Diketopiperazines formed in roasting taste bitter at just 20 milligrams per liter, and an espresso holds 20 to 30 milligrams.