While Barley is the traditional grain for brewing, many breweries will substitute corn, rice, wheat, rye or other grains for a portion of the malted barley. All grains must be malted. Malting is a natural process that develops sugars, soluble starches and other characteristics desirable for brewing beer. Grain is malted by controlling germination and stopping it at a point which accentuates the above mentioned qualities. Hops are green cone like flowers that grow on vines.
Hops impart a bitterness to beer which balances the sweetness of the malt.
Hops also add aroma, enhance head retention and inhibit spoilage. The most important aspect of hops are their bittering units. The bitterness derives from an acid, alpha acid, in a resin called lupulin. Hops can be purchased whole, in pellets or as an oil. Everyone has their own preference.