Understanding Bacteria and Biogenic Amine Production for Brewing Sour Beer

Both WildBrew Helveticus Pitch™ and WildBrew Sour Pitch™ were carefully selected for their high quality of lactic acid production as well as their ability to be used safely in a brewery environment (for example, their low level of hop tolerance), but there is more to consider when selecting a souring bacteria in brewing. Recently, we undertook a research project to understand another quality control parameter – biogenic amine production.

What are biogenic amines?

Biogenic amines are small nitrogen compounds found in fermented foods and beverages and are a result of a type of lactic acid bacteria metabolism of amino acids. Specifically, biogenic amines are the result of lactic acid bacteria stimulating an enzymatic process, known as decarboxylation, of certain amino acids. Some common examples of biogenic amines are:

• histamine,
• tyramine,
• cadaverine,
• and putrescine.

For the most part, biogenic amines can be safely digested by humans in food. However, at higher levels (histamine above 50mg/kg), the body’s detoxification can struggle, resulting in headaches and other allergic reactions, depending on the body’s sensitivity. Apart from the
health concerns, biogenic amines that have been extensively studied in wine, have been found to bring undesirable aromas and flavor, for example masking wine aromatics or producing meaty aromas.

• Histamine – affects health
• Putrescine – masking effect
• Cadeverine – masking effect, seafood aroma flavor

In beer, high levels of cadaverine have been found to present an undesirable shrimp/seafood aroma and flavor. In order to ensure biogenic amines are limited or not present in beer, bacteria selection is of crucial importance.

Testing biogenic amines in several souring methods

We undertook a study to examine the production of biogenic amines under kettle souring conditions fermented with LalBrew Nottingham™ ale yeast. A 20hl 12°P wort was made and split into 7 different batches between:
A control (LalBrew Nottingham™ yeast)

• WildBrew Sour Pitch™
• WildBrew Helveticus Pitch™
• WildBrew Philly Sour™
• Sourvisiae^®

Individual kettle sour batches were conducted using Wildbrew Sour Pitch™, Wildbrew Helveticus Pitch™, and 37°C. These kettle sour batches were then fermented with Nottingham at a 0.75g/l pitch rate and a 20°C fermentation temperature. The results of this study found that Wildbrew Helveticus Pitch™ and WildBrew Sour Pitch™ did not produce histamine, tyramine, or putrescine. A very small amount of cadaverine, 8mg/l for Helveticus Pitch and 10mg/l for Sour Pitch, was created; however, both levels were significantly less than sensory impact.

The lack of biogenic amines found with selected bacteria is notable compared to spontaneously fermented beers. As the name suggests, spontaneously fermented beers are beers made with inoculations from the wild, often using a coolship. Levels of biogenic amines in these beers have ranged from 9-39mgl (histamine), to 26-50mg/l (putrescine) and 41-78 mg/l (cadaverine). These levels are noticeably higher than some tolerances listed by regulation authorities – for example the Swiss Food Regulation has listed histamine tolerances in wine to be about 10mg/l. Ethanol inhibits the normal detoxification processes in your body, so there is greater sensitivity to biogenic amines in alcoholic beverages. Therefore, tolerance limits for these compounds in alcohol are lower.

There are a variety of methods to make a sour beer with different organisms, with new ones being discovered or used all the time. However, it is important to understand that while these organisms may be able to produce acidity, they may also produce other undesirable compounds. Therefore, it is crucial that brewers choose their selected bacteria carefully and have a thorough understanding of their chosen production method.