It’s understandable why bitterness is an acquired taste. Despite what surely must pain “iso-philes” (bitter beer lovers), the old “bitter beer face” commercials have some truth to them. It’s generally agreed that bitterness has been an evolutionary signal for a possible poison, so it’s no surprise if we are initially put off the taste of bitterness.
What’s not quite so understandable is how the sensation of bitterness differs for each of us. Much of the research I’ve been involved with has shown that various bitter compounds elicit different responses from each person, with few correlations able to be drawn. Each compound has different intensities and often different qualities as well, including harsh, medicinal, vegetative, lingering, etc.
The predominant source of bitterness in beer are the iso-alpha acids. These are derived from the alpha acids which are present in the flowers of the female hop plant, Humulus lupulus. These alpha acids are found in the lupulin glands of the flower, which look like tiny yellow pollen-like balls clustered together. Much of the other material in the hops which brewers value (such as aroma compounds) are also contained in the lupulin glands, but today we discuss the alpha acids.