Yeast is probably the most important part of your beer as after all, these fungi are what turns wort into a delicious beer. Besides being the key ingredient that actually ferments wort into beer, yeast is responsible for almost every flavor you experience in beer. Although many brewers recognize the importance of hops, yeast actually plays the most important role when it comes to flavor and aroma.

So what is it about yeast that we find so interesting? Can you make beer with bread yeast? The truth is you can make beer with any type of yeast but maybe your result will not be as delicious. Brewers yeast is a special type of yeast that has been improved through centuries and has many properties that make it beneficial to make the best beer.

The decision maker

Different strains of yeast absorb different amounts of every flavor and aroma-producing compound in the wort. This means that yeast decides not only what flavor compounds to produce but also which ones they leave alone. Yeast can absorb and transform the alpha acids produced by hops so yeast can greatly affect how bitter or aromatic the final beer is.

Of course, yeast greatly affects the flavors of the malt. After all, yeast eats all the sugars from the malt to produce alcohol and other flavor compounds. So how yeast interacts with the beer malt base is probably the most important way yeast can affect the beer flavor.

Dry or liquid yeast

Long before the discovery of yeast much less its domestication for beer the ancient Romans discovered uses for dried yeast. Yeast grows and lives in water. However, it can be stored for long periods if dried once grown. The Romans used to take concentrated dough full of yeast and leave it in the sun. This dried the yeast so that they could be revived with sugars later.

Today most of the yeast for bread and the wine industry is in dried form. But brewers remain strong proponents of liquid yeast. The sugars that are used to revive dried yeast are glucose instead of the abundant maltose found in malt sugars. This means that yeast that has never been exposed to maltose won’t begin the fermentation process as fast as liquid yeast. In addition, the yeast drying process isn’t quite sterile, increasing the infection chances during fermentation which means possible bad beer. So brewers prefer liquid yeast.

Selective breeding

Flocculation is the special ability of brewing yeast that allows them to clump together after the fermentation is complete. And either rise to the top of the beer or settle on the bottom of the fermenter. Most species of wild yeast are not flocculent and would make consistent flavors across batches of beer almost impossible.

However, brewers are smart and over the centuries they found that it was much easier to just grab some sediment from the bottom of the fermenting vessel and throw it in the next batch than it was to try to recreate the same yeast conditions. This led to the property of flocculation being naturally selected into brewing yeast. And this property is really important because it allows brewers to not only reuse yeast but it also allowed them to experiment with the natural selection to bring out other yeast traits. Without flocculation, natural selection for other properties would have been much harder. As the yeast would have remained in solution in the beer thirsty people would have drunk away all your hard work.

Most types of brewing yeast have lost their ability to reproduce sexually. Although wort is a great place full of food and lacking of competitive bacteria and predators, yeast unfortunately don’t get together to make more little yeast. Instead, they were naturally selected to reproduce asexually which involves getting about two-thirds of their body weight in food in a short period and then expelling a small carbon copy of themself. This allows brewers to make more consistent tasting beer between batches.

The benefits of unfiltered beer

Unfiltered or unpasteurized beer can be a good source of probiotic yeast. Your gut is filled with a variety of bacteria and yeast that help you digest food. Some unfiltered beers can contain yeasts that thrive inside the body and do a great job of breaking down certain chemical compounds in food that can otherwise be harmful. This is especially true of unfiltered sour beers which contain some of the similar yeast to those in yogurt.

At its core, the filtration process in beer-making serves three major purposes. Firstly, it’s done to clarify the beer. Clarity is often equated with quality in the minds of many beer consumers, making it a desired attribute.

Secondly, filtration aids in enhancing the beer’s stability. This means preventing the development of off-flavors or unexpected changes in the brew over time. Lastly, it ensures consistency. Brewers want their beer to offer the same taste, appearance, and quality across different batches, and filtration aids in achieving this uniformity.

When we talk about unfiltered beer, we’re referring to beers that skip this filtration step, leading to some interesting effects. In simple terms, unfiltered beer is a type of beer that retains certain components—namely, yeast and grain particles—that are usually filtered out in the beer-making process. By allowing these components to remain, brewers create a beer that offers a different drinking experience. The production of unfiltered beer mostly mirrors the conventional brewing process, with one significant exception: the beer is not subjected to filtration after fermentation. This omission allows the yeast, along with other substances, to stay within the beer, resulting in a brew that carries a more robust flavor profile, a distinctive appearance, and a character quite unlike its filtered counterparts. Unfiltered beer retains more of the vitamins and proteins inherent in yeast, which are typically removed during filtration. This means that, in comparison to filtered beer, unfiltered beer might be more nutritious, offering a greater range of B vitamins and amino acids. The yeast in unfiltered beer can also play a beneficial role in gut health. Acting as a probiotic, it can help maintain a healthy balance of gut flora. However, it’s essential to remember that these benefits don’t grant unfiltered beer a “health food” status—it’s still an alcoholic beverage and should be consumed in moderation.