When Good Yeast Goes Bad: The Dark Side of Brewing with Beer Yeast Infections


When Good Yeast Goes Bad: The Dark Side of Brewing with Beer Yeast Infections

The Magic of Yeast in Brewing

Yeast is an essential ingredient in the brewing process of many alcoholic drinks such as beer, wine, and spirits. It is responsible for converting the sugars in the malt or fruit juices to alcohol, carbon dioxide, and other by-products that contribute to the final flavor and aroma of the drink.

But not all yeast strains are created equal, and not all of them are desirable in the brewing process. Sometimes, good yeast can turn bad and cause infections that can ruin the batch of beer, wine, or spirits.

Types of Yeast Infections

Yeast infections can occur at any stage of the brewing process, from the wort to the finished product. They can be caused by contamination from the environment, poor hygiene, or the use of infected equipment.

Some of the most common types of yeast infections in brewing include:

  • Brettanomyces
  • Lactobacillus
  • Pediococcus
  • Acetobacter
  • Kloeckera
  • Saccharomyces var. diastaticus

Brettanomyces: The Wild Card

Brettanomyces is a type of yeast that can turn good beer into bad beer, but it can also turn bad beer into good beer. It is a wild card in the brewing world, and many brewers love it for the unique flavors and aromas it imparts to their beers.

However, Brettanomyces infections can also cause off flavors and aromas that are not desirable in certain beer styles. These infections are often referred to as “Brett funk” and can range from a subtle barnyard aroma to a full-blown sourness that can be overpowering.

Lactobacillus and Pediococcus: The Souring Agents

Lactobacillus and Pediococcus are types of bacteria that are desired in certain beer styles such as sour beers, but they can also cause infections that can ruin a batch of beer.

These bacteria produce lactic acid, which can result in an acidic or sour flavor that is desired in sour beers but not in other beer styles. Lactobacillus infections can also cause a gushing effect in the bottle due to the production of carbon dioxide.

Acetobacter: The Vinegar Producer

Acetobacter is a type of bacteria that can turn beer into vinegar. It produces acetic acid, which gives vinegar its characteristic sour taste and aroma.

Acetobacter infections can be caused by exposure to oxygen during the fermentation process or by contamination from infected equipment. They can be prevented by maintaining good sanitation practices and minimizing exposure to oxygen.

Kloeckera and Saccharomyces var. diastaticus: The Fermentation Offenders

Kloeckera and Saccharomyces var. diastaticus are types of yeast that can cause fermentation problems in beer and wine.

Kloeckera infections can lead to a yeast-like off flavor and aroma and can cause a drop in alcohol content due to its ability to convert ethanol to ethyl lactate.

Saccharomyces var. diastaticus is a mutation of the common brewing yeast Saccharomyces cerevisiae. It is known for its ability to ferment complex sugars that other yeasts cannot ferment, leading to high attenuation levels and a dry finish. However, it can also cause overcarbonation and gushing in beer bottles.

Frequently Asked Questions

Q: How can I prevent yeast infections in my beer?

A: The best way to prevent yeast infections in your beer is to maintain good sanitation practices and minimize exposure to oxygen. This includes cleaning and sanitizing all equipment and surfaces that come in contact with the beer, using proper yeast handling techniques, and avoiding exposure to contaminated air.

Q: Can I salvage a beer that has been infected with Brettanomyces?

A: It depends on the severity of the infection and the desired outcome. Some brewers intentionally infect their beers with Brettanomyces to achieve a specific flavor profile. However, if the infection is causing off flavors and aromas that are undesirable, it may be difficult to salvage the beer without sacrificing its quality.

Q: Can I still drink a beer that has been infected with bacteria?

A: It depends on the type and severity of the infection. Some bacteria produce desirable flavors and aromas in certain beer styles, while others can cause off flavors and aromas that are not desirable. If you are unsure, it is best to consult with a professional brewer or beer expert before consuming the beer.

Q: Can I reuse equipment that has been contaminated with yeast?

A: It is not recommended to reuse equipment that has been contaminated with yeast without first cleaning and sanitizing it thoroughly. Yeast can survive on surfaces and equipment for a long time and can contaminate future batches of beer if not properly cleaned and sanitized.

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