Water

More than 90% of beer is water. Small wonder then that the breweries place high requirements on the quality of the water used. Breweries generally get their water from a well or spring, or they use tap water. There are many salts and minerals in the water, the quantity and variety of which affect the ultimate flavour of the beer.
The minerals in the water will also influence the head formation.

Malt

Malt is the sugar to be fermented that comes from the grain. Barley is generally used, although sometimes wheat and occasionally oats or spelt. Inferior raw materials for malts are maize and rice. Japanese Saké is made from rice (some people classify saké as a beer). Grain cannot ferment by itself. When the grain is left in water, allowed to germinate and then dried, fermentable sugar is released. This procedure is called malting. Barley malt is by far the most important sugar-containing raw material for producing beer. Only malted barley can be used in the brewing process. Wheat on the other hand can be used in both the malted and unmalted form for beer production. Wheat is used in the so-called wheat beers, including white beer and lambic.

Sugar

In addition to the malted grain, sugar is often also added to help the fermentation.

Hops

Hops give beer its bitter flavour and are also a natural preservative. Only the flowers from the female hops are used for beer. The hop flowers contain lupulin, a resinous substance that gives the typical bitter flavour. Hops also contain substances that make the beer last longer.
Hops are grown in Belgium, but are generally imported from abroad. There are a number of varieties that the brewer can choose from or combine together. When the bitter flavour must predominate, young hops tend to be used. If the hops are not to overload the flavour, then hops over a year old are a good choice. Lambic, for example, has enough flavour in itself and requires no additional bitterness.
Hops also contain isoflavons with phyto-oestrogens These substances are of more importance in functional nutrition.

Yeast

Yeast is a single cell micro-organism. It is needed in the brewing process for converting fermentable sugars into alcohol and carbon dioxide. Before the process has got very far, the water and malt are boiled together into wort. After cooling, the yeast is added. When converting sugar into alcohol many types of aromatic substances are formed that also determine the character of the beer. Most breweries have their own jealously guarded yeast cultures, sometimes consisting of a number of colonies.
A distinction is made between two types of yeast according to its behaviour during the fermentation process: top yeast and bottom yeast. Top yeast stays on the surface of the beer mixture and ferments at around 10°C to 20°C, while bottom yeast ferments at 5°C to 10°C. In this last case, the yeast cells sink to the bottom.

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