The brewing value of hops depends on the resin fraction which amounts to 15%, and the essential
oil, comprising ∼0.5%. Total resin is defined as the material soluble in both cold
methanol and diethyl ether; “soft” resin is that proportion of the total which is
soluble in hexane comprising mainly α and β-acids, while “hard” resin is insoluble
in hexane. The α-acids that are the most significant bittering precursors can be
distinguished from other soft resins from their ability to form a lead salt which is
insoluble in methanol. The determination of moisture and seed content also provide
useful conclusions about their quality (13). Adjuncts of carbohydrate origin other