What Is an Infection?
An infection refers to the introduction or presence of undesirable microorganisms in beer or raw materials. When these undesirable microorganisms are present in beer and start competing for sugar with cultured yeast, infection can occur. Bacteria or undesirable microorganisms from wild yeast can ruin beer. Infection is the most feared situation for both novice and professional brewers. The severity of the infection may be difficult to judge by appearance alone. In extreme cases, infection can cause beer to become cloudy, sour, or smelly, making it unsightly or undrinkable. Although beer infection is not harmful to human health, allowing infected beer to reach consumers can be very damaging to the reputation and business of any brewery.
Life essentially depends on sugar, and many organisms can undermine the flavor of beer. Spoilage organisms that tolerate oxygen and thrive before fermentation lowers the pH of the wort and produces ethanol are sometimes referred to as “wort breakers.” Additionally, there are bacteria known as “beer destroyers,” which tend to prefer anaerobic conditions and can survive well in a lower pH and alcoholic environment. Most brewers believe that the most common beer-destroying organisms include Lactobacillus, Pediococcus, and wild yeast such as Brettanomyces. Each type of bacteria has its preferred nutrients, temperature range, pH range, and growth rate.
Infection is a frightening situation for both brewers and consumers. However, certain beer styles require or even encourage infection, including Berlin Weiss beer, Lambik beer, and Belgian-style sour beer. What one brewer considers an infection may be the taste complexity desired by another brewer, especially in the realm of sour beer styles. However, for most beers, brewers aim to exclude all other biological factors by adding the necessary raw materials to the brewing equipment.
How Does Infection Develop in Beer?
Infection may occur during the wort cooling, fermentation, cold transfer, and packaging processes following the boiling of the non-toxic wort in a kettle. This situation generally arises from improper cleaning of brewery equipment. Additionally, bacteria or microorganisms may accidentally enter the beer during ingredient addition before fermentation. Infection can also occur during cold transfer or packaging.
How to Determine if Beer Is Infected?
The presence of an oily gloss on top of the beer resembling a thin, white ice cap with jagged edges is a sign of the initial stage of infection. This kind of infection is usually caused by wild yeasts like Brettanomyces or wild bacteria like Lactobacillus. In more severe infections, the biofilm layer known as a “pellicle” may appear wavy or bubble-like with a belt. Although they may seem like different types of infections, they are caused by similar strains of bacteria or yeast.
Biofilms only form in aerobic conditions and serve as protection for wild yeast and bacteria against oxygen because they prefer an anaerobic environment. Therefore, even without visible pellicle formation, your beer may still be infected if it was not exposed to oxygen during the fermentation process. In such cases, the only way to determine if it is infected is to taste it.
There is no need to worry about getting sick from tasting beer as these wild bacteria, yeasts, or molds will not harm you. If the beer tastes bad or smells off, it is advisable to discard it. However, in some cases, infection may improve the flavor of the beer. Remember, popular sour beers are brewed using these wild yeasts and bacteria.
How to Resolve Beer Infection?
The best way for brewers to combat harmful microorganisms in finished beer is to ensure proper sanitation of fermentation tanks, bright tanks, and filling equipment. Following a good cleaning and disinfection program is crucial. If you are using stainless steel brewing equipment, avoid using detergent for disinfection as it can cause irreversible damage to the stainless steel.
Furthermore, the use of sterile bottles and barrels is also recommended. In breweries, especially large industrial ones, beer is sent through aseptic filtration or pasteurization on the bottling line after packaging. These steps help extend the shelf life of beer by removing or killing potentially infectious microorganisms, ensuring that consumable beer is more likely to reach the tables of consumers. Although pasteurization kills microorganisms, improper handling can result in a stale or “cooked” taste and aroma. Sterile filtration can remove bacteria but may also strip beer of its taste, aroma, body, and even color.