Most beer is fermented with a brewer's yeast and flavoured with hops. Secondary starch sources (adjuncts), such as maize (corn), rice, or sugar, may also be used. Less widely used starch sources include millet, sorghum and cassava.The amount of each starch source in a beer recipe is collectively called the grain bill.hen the fermentation is complete the brewer may rack the beer into a new tank, called a conditioning tank. Conditioning of the beer is the process in which the beer ages, the flavour becomes smoother, and flavours that are unwanted dissipate.