In general, beer is made up of 4 main ingredients. Below is a list of these basic ingredients as well as the affect that they have on the taste, aroma, and color of beer.
Water
This delicious combination of hydrogen and oxygen makes up 90% of beer.
The Effect: The specific minerals in water give distinct flavors to the beer it is used in. Many breweries use water from natural springs that contains unique mineral content depending on the environment it is taken from. This gives many brews unique characteristics. Other breweries chemically adjust their water to give it the desired mineral content for the beer they’re brewing.
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Malted Barley
Barley is grain that looks similar to wheat. In order for it to be used in brewing, barley must be malted, the first step in the brewing process. Barley types are distinguished by the number of seeds growing at the top of the stalk. Traditionally, European brewers prefer 2-Row barley because it malts the best and American brewers prefer 6-Row barley because it has a higher concentration of enzymes and it is more economical to grow. Barley can be replaced by other ingredients for the malting process. Wheat, corn, and rice are commonly used for flavor, body, and cost reasons.
The Effect: Sweetness in beer comes from the malted barley. The color of beer is determined by the degree of drying and roasting the malted barley gets; temperature and duration.
The flavor imparted by the malt is also determined by the degree of roasting. Kilned and lightly roasted barley leaves sweet, caramel, candy-like, and raisiny flavor notes. With higher temperatures and lengths, roasting can give nutty, smokey, toasted, and coffee flavors.
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Hops
Hops are the flowers that grow on the vines of the hop plant. There are many varieties of hops. Brewers choose their hops based on the desired amounts of bitterness and the aromas associated with different varieties of hops.
The Effect: Hops balance the sweetness of the malt with their bitterness, stabilize and preserve beer, and contribute greatly to a beer’s aroma. The effect the hops have on the final product depends on when they were added during the brewing process.
Hops that are added during the boiling of the wort are known as ‘bittering hops’ and contribute to the bitterness of the beer. The earlier hops are added to the boil, the more bitterness that can be extracted from them. Hops added during the final minutes of the boil contribute to the aroma of the beer. A smaller degree of flavor comes from the hops when they’re added at this stage of the boil. Hops can also be added after the wort has cooled down and has been fermented. These hops don’t add bitterness but only contribute aroma to the beer.
Flavor comments such as flowery, spicey, earthy, piney, and citrusy can be attributed to hops.
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Yeast
Usually in liquid form, yeast is the living fungus that makes it all happen. Yeast converts the most of the sugars of the wort into alcohol and carbon dioxide. It comes in three main types: Top Fermenting Ale Yeast, Bottom Fermenting Lager Yeast, and Wheat yeast.
The Effect: Besides the main byproduct of fermentation, alcohol, there are other byproducts that add to flavor and aroma of beer. Top Fermenting Ale Yeast has byproducts that generally produce fruity and flower tastes and aromas. Bottom Fermenting Lager Yeast produces less fruity notes and let the aroma from the hops come through. Wheats Yeasts are known to produce clove and banana notes. Butterscotch and woody tastes are also attributed to yeast depending on the type of beer brewed.
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Others
Apart from the four basic beer ingredients above, many breweries stray away from the Reinheitsgebot and add fruit, spices, honey, and much more for new and interestingly flavored beers.