Yeast is one of the most important ingredients in beer making. Through the biological process called ethanol fermentation, yeast can convert sugar into alcohol and carbon dioxide, two features that define beer.
After fermentation, many large commercial breweries remove live yeast through filtration and pasteurization. Beers from small craft breweries, on the other hand, will often contain live yeast used to carbonate their bottles.
Let’s take a look at the important role yeast plays in the brewing process and the different ways breweries use or remove yeast after primary fermentation, and why.
Is there still live yeast in beer?
Most people know that yeast is an integral part of the beer brewing process.
While every beer ever made has been in contact with yeast at some point, modern filtration and pasteurization methods can remove live yeasts left in the beer. However, some traditional and craft breweries leave behind some live yeast to carbonate and bottle condition their beers.
Yeast is the main agent used in beer making that makes beer contain alcohol. Through ethanol fermentation, yeast transforms sugars into ethanol and carbon dioxide. Without yeast, the carbonated, alcoholic beverage we call beer would be impossible to make.
After fermentation, yeast will become dormant and sink to the bottom of your fermenter, forming sediment sometimes called trub.
Through filtration and pasteurization, yeast can be removed from the beer. These methods are incredibly common in commercial breweries, meaning that most mass-market beers will not contain any live yeast.
Is yeast in beer bad for you?
Because certain varieties of yeast can cause dangerous infections, it may be difficult to accept that this microscopic organism is an essential part of beer brewing. Yet there’s no need for concern; Saccharomyces cerevisiae, also known as brewer’s yeast, is only distantly related to harmful yeasts.
The yeast used in beer is almost always safe for human consumption and has actually been shown to be a powerful probiotic for most people. However, those who have a yeast allergy or intolerance, or are taking certain medications should avoid consuming brewer’s yeast.
In addition, you might suffer from a yeast intolerance if you notice any of the following symptoms after eating fermented products:
- Abdominal swelling
- Difficulty breathing
- Joint Pain
Although it is exceptionally rare, researchers have diagnosed a handful of patients with an allergy to yeast. There is a possibility that this condition is underdiagnosed, though, so if you have a history of developing itching or rash after drinking beer, wine, and cider, you may be allergic to yeasts.
Despite these exceptions, brewer’s yeast is entirely safe for most people. In fact, one strain of brewer’s yeast has been shown to support healthy digestion by increasing the bioavailability of minerals, removing toxins from food, and improving gut health. Though the benefits of the varieties of yeast used most commonly in brewing have not been studied, researchers suspect that they would provide similar probiotic effects.
What beers contain yeast?
Because of the vital role yeast plays in the beer-making process, there is not a single kind of beer that does not come into contact with yeast. There is, however, some variation when it comes to the variety and amount of yeast in different beers.
One variation you might encounter in the brewer’s yeasts is the specific strain used. The most common kind of brewer’s yeast, S. cerevisiae, is used for ales and many other kinds of beer whereas its cousin, S. pastorianus, is traditionally used for lagers. Two distant relatives, Torulaspora and Brettanomyces, are also used for lambics, weissbier, and a number of other Belgian-style beers.
In addition, the post-fermentation processing of a beer will greatly impact the yeast content seen by the consumer. For example, processes like pasteurization and filtration are often used to remove excess yeast after fermentation is completed. Different production methods employed by large-scale commercial breweries and craft breweries vary widely in this regard.
Mainstream commercial beers
Beers produced for large-scale production and sale will contain very little yeast, and any that remain will have been killed by the pasteurization process.
Commercial breweries choose to filter and pasteurize their beer to improve shelf stability and encourage uniform flavor. This is because yeast continues to affect the flavor carbonation of beer when stored at room temperature, which can decrease shelf-life and produce off-flavors.
Next, the beer is pasteurized by holding it at 140°F for about 15 minutes to kill any yeast or other microorganisms that might remain.
In contrast to large-scale breweries, craft breweries often forego industrial filtration and pasteurization processes. Because craft beer is usually sold locally in small batches, shelf stability is less of a concern. Additionally, bottle conditioning beer with live yeast can both improve flavor and save big by avoiding expensive industrial machinery.
Many traditional Belgian breweries and American craft breweries choose to bottle condition their beer instead of relying on commercial carbonation equipment. Even larger craft labels like Sierra Nevada bottle condition their beer with the goal of deepening the flavor profile of their brews.
The presence of live yeast in beer has scientifically proven benefits on the quality of beer. Some of these benefits include:
- Higher saturations of carbon dioxide (resulting in denser, more stable foam)
- Transformation of residual amino acids into flavor compounds
By transforming flavorless amino acids into delicious esters, well-made bottle-conditioned beer will have a fuller flavor made up of warming notes and floral, fruity aromas.
However, the beneficial effects offered by bottle conditioning are immediately counteracted when the yeast begins to die and break down. When they begin to decompose, the yeast releases amino acids that counteract the improved flavors and can even produce unpleasant off-flavors. For this reason, it is especially important to properly refrigerate bottle-conditioned craft beer.
When brewing beer at home, you will have to decide for yourself how you want to deal with the yeast left in your homebrew. While many brewers simply siphon their beer for the top and leave the yeast sediment in their fermenter, there are a number of more sophisticated techniques that you can use to remove yeast after primary fermentation.
Filtration is a common and relatively easy process for homebrewers. With the proper equipment, you can safely filter your beer down to about 1.0 or 0.5 μm. Using a filter any finer than that can risk removing flavor compounds, though.
Chemically Disabling Yeast
A common technique used by winemakers, chemically disabling yeast using potassium sorbate can prevent yeast from reproducing, shutting down the fermentation process. This method is not sufficient by itself, however.
Modern yeasts have become resistant to potassium sorbate, and even non-resistant but longer-lived yeast can continue to ferment until they die out. Because of this, this method is usually used in combination with chilling and filtration techniques to remove yeast without pasteurization.
It is very easy to pasteurize beer at home. All you have to do is hold your beer at about 140°F for 15 minutes. Pasteurization will not remove any particulate from your beer, and dead yeast can produce off-flavors, so be sure to filter your beer before pasteurization.
When it comes to carbonating your beer, many homebrewers carbonate their beer by bottle conditioning it with live yeast. If you prefer to keep your finished beer free from yeast, you can force carbonate your beer in bottles of kegs.
Pros/Cons of Keeping Live Yeast in Your Homebrew:
- Improved shelf life at room temperature
- Standardized flavor
- Lost flavor compounds and aromas
- Destroy probiotics
- Takes more work
Does any beer not have yeast?
Like any fermented beverage, beer can only be made with the help of ethanol fermentation. And while ethanol fermentation is not exclusive to yeast, they are the most prolific fermentors known to man.
One bacteria, Zymomonas mobilis, can produce enough ethanol to ferment alcohol, but it is considered a contaminant in beer because of the sulfur-like esters it produces.
Because nothing does the job quite like yeast, every beer you ever taste will have been made with the help of yeast.
Is there any way to completely remove yeast from beer?
The best way to remove yeast from beer is through filtration. The smallest yeasts are between 3-4μm, which is much larger than some of the finer filters used by beer makers. But when the yeast dies and begins to break down, they release small particles into your beer that are much harder to filter out. So while it is easy to find filtered, pasteurized beer without any living yeast, it is almost impossible to remove all traces of yeast in a beer.