Beer is an alcoholic beverage produced by the saccharification of starch and fermentation of the resulting sugar. The starch and saccharification enzymes are often derived from malted cereal grains, most commonly malted barley and malted wheat. Most beer is also flavoured with hops, which add bitterness and act as a natural preservative, though other flavourings such as herbs or fruit may occasionally be included. The preparation of beer is called brewing. A shooter is a neologism for an alcoholic mixed drink that contains one ounce (33 ml) of two or more spirits. Some shooters also have a non-alcoholic ingredient. They are generally drunk quickly, rather than being sipped. Shooters can be shaken, stirred, blended, layered, or simply poured. Shot glasses or sherry glasses are the usual drinkware in which shooters are served. They are most commonly served at bars, and some bartenders have their own "signature" shooter. The ingredients of shooters vary from bartender to bartender and from region to region. Two shooters can have the same name but different ingredients, resulting in two very different tastes.