Hops

Hops are the green flowers, also called seed cones or strobiles, of the hop plant Humulus lupulus, a climbing perennial in the Cannabaceae family. Brewers use them chiefly as a bittering, flavouring and stability agent in beer, where they add floral, fruity or citrus notes alongside bitterness, and they also appear in some other drinks and in herbal medicine. Only female plants are grown commercially, so that the cones stay seedless, and the vines are trained up strings in a hopfield. The cones carry a yellow, waxy lupulin whose lupulone and humulone suppress bacteria and so favour the brewer's yeast. The earliest documented hop cultivation dates to 736 in the Hallertau region of present-day Germany, and hops slowly displaced the older gruit herb mixtures from the 13th century. Harvested bines are dried in an oast house or kiln and often pressed into pellets, and Germany and the United States grow about three quarters of the world crop.