The 4 main ingredients in beer are water which makes up at least 90% of the beer; grains or malts which are a source of starch capable of being fermented; hops which provide flavor and aroma as well as offsetting the sweetness of the malt; and yeast which converts the grain’s starches into alcohol and carbon dioxide.
Water
Considering that 90% of a beer is water it goes without saying that is important that it comes from a high-quality source. This is a point that many novice brewers miss, when it comes to making beer all water is not created equal. In particular, the composition of the water plays a large part in determining the quality and flavor of beer, with the mineral content being of the utmost importance.
Water that is soft or has a lower mineral count is ideal for making beers that are considered to be smooth, crisp, and clear. On the other hand, harder water or water with a high mineral count is better for making bitter-tasting beer. This is why certain styles of beer originated in different parts of the world. Brewers in those days could not modify the minerals in the water, resulting in beers that best suited the local water source being primarily what they brewed.
Examples of the makeup of the local water source determining what beers were brewed in certain regions Stouts from Dublin Ireland, Vienna Lagers from Vienna Austria, Wheat beers from Bavaria Germany, Pilsners from Pilsen Czech Republic, and Pale Ales from Burton-on-Trent in England.
Nowadays, there is software available to allow brewers to make adjustments to their brewing water and allow them to be able to brew pretty much any style of beer with any quality water source.
Grains or Malts
It’s hard to say that grains are the single most important ingredient in beer because without water there would be no beer, however, they arguably have the largest influence on the characteristics of any beer. Malts are largely responsible for the aroma and taste of the beer as well as the color, mouthfeel, and head, not to mention that without the fermentable starch from the grains there would be no alcohol in beer.
The most commonly used types of grains in making beer are for the most part the same grains used for making cereal, i.e. Barley, Oats, Wheat, Rye, Rice, and Corn.
As a result of its composition Barley is the primary grain used in making beer. Its kernels are perfect for brewing as the starches within them can easily and quickly be broken down into fermentable sugar. Barley also contains a large amount of starch per grain which provides more fermentable sugars and allows for a higher alcohol content per amount of grain used compared to the other malts.
Barley is also made up of a large amount of protein which gives the beer its body and head retention. Another benefit of using barley is during the brewing process itself, its husks are strong and act as a filter during what is referred to as the lautering which is basically the rinsing stage where the sweet liquid (wort) is separated from the grains.
Oats were traditionally used in making Stouts as they provide a rich, smooth and soft mouthfeel and texture. They can also make the beer appear hazy or cloudy and have a fuller mouthfeel; as a result, you will now see oats being used in many different beer styles such as NEIPAs and Pale Ales.
Wheat is also loaded with proteins which allow this grain to create a thicker body, and mouthfeel as well as a thick long-lasting head. It can also provide for a soft and smooth mouthfeel as well as a hazy appearance.
Rye is typically used to add flavors such as spice, carmel, and chocolate depending on how it is kilned. It also is used to dry a beer out and add crispness. It typically does not make up a large percentage of the grain bill as it does not have a husk and as a result during the lautering stage causes problems as it can clump up and not allow the sugars to be rinsed.
Corn & Rice do have their place in beer recipes however they get a bad name as they are a cheaper grain and as a result, the large commercial breweries tend to use them in larger amounts than they should; which results in a watered-down flavorless beer. However, if used correctly corn can provide a smooth sweetness to the beer while lightening its body and improving its clarity. Rice can also be used to lighten the body while providing crisp flavors and a dryer profile.
Hops 
Although beer is thousands of years old, hops did not become one of its main ingredients until the 9th century. In recent years hops have become synonymous with the craft beer movement with beers now being brewed with much higher levels of hops than ever before. Beers such as NEIPAs and West Coast IPAs are known for their abundance of hops.
Hops are green cone-shaped flowers from a Humulus lupulus plant and provide a few things to a beer, the first being that it balances the flavor profile of the beer by offsetting the sweetness from the malt by adding a level of bitterness. They are also known for providing for a large part of a beer’s aroma and some of its flavor. Another beneficial quality of hops is that they are a preservative and one of the main reasons brewers of days gone by started using them, they preserved the beer longer and allowed it to be shipped long distances.
There are now hundreds of varieties of hops with new strains being created on a regular basis; each has its own flavor, aroma, and bitterness level that it brings to the beer. Depending on when during the brewing process the hop is added will also determine what characteristics it provides to the beer. Hops added at the start of the boil are for bittering, while hops added during the middle of the boil are for flavor, and hops added at the end of the boil and during fermentation are for aroma.
Yeast
Yeast is a vital ingredient in beer as it converts the sugar and starches from the grains into alcohol and CO2. Without yeast, beer as we know it would not exist.
When it comes to yeast there are 3 main types, wild yeast, ale yeast, and lager yeast.
Before people understood yeasts’ role in the production of alcohol and figured out how to produce and harvest it, wild yeasts were how alcohol was made. Today many of the sour beers on the market are produced using a strain of wild yeast to ferment them.
The other two types are the main categories of yeast…
Ale yeast is also referred to as a top-fermenting yeast. It requires warmer temperatures and typically ferments out very quickly.
Lager yeast is referred to as bottom-fermenting yeast. It requires lower temperatures and as a result, takes longer to ferment. As a result of this style of yeast and the colder temperatures, the beer is typically clearer, crisper, and cleaner.
There are also many different strains of yeast within these two categories that a brewer can choose from. Depending on which strain you choose will play a significant role in how the beer tastes. Two beers can have the exact same ingredients except for the yeast and they will taste and even at times look like two distinctively different beers.
Additional Beer Ingredients
The German Purity laws of 1516 actually ruled that these 4 main ingredients in beer were to be the only ingredients used in the production of beer; and in many parts of the world, they are all that is still used, however in the rest of the world many brewers do add additional ingredients to include fruit, juice, jam, coffee, flowers, and chocolate to name just a few.
P.S. If you brew your own beer be sure to pick up your gift or Big Robb’s top 5 favorite beer recipes from his brewpub. Details are on the side of the blog or at the bottom if you are on your phone. Cheers