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 otherthan malt are sometimes used as an additional source of extract to supplement
malt. Unmalted cereal adjuncts usually contain no active enzymes and therefore
rely on malt or exogenous enzymes to provide the necessary enzymes for starch
conversion (19).