Chloe Zhang
Fermentation is a crucial process in brewing beer, but it can also introduce unwanted off-flavours. One of the most undesirable off-flavours is a plastic taste, which is challenging to disguise or tone down. While the specific cause of plastic off-flavours is debated, potential sources include chlorine in sanitizing solutions, wild yeast or bacteria contamination, and temperature fluctuations during fermentation. To prevent plastic off-flavours, brewers must ensure thorough sanitation, control fermentation temperatures, and use appropriate materials like glass carboys instead of plastic fermenters.
| Characteristics | Values |
|---|---|
| Plastic off flavor caused by | High fermenting temperatures, Brett infection, floating thermometer, garden hose, or any plastic that touches the brew |
| Plastic off flavor described as | Plasticky, rubbery, bandaid flavor, or adhesive flavor |
| Plastic off flavor in beer | One of the worst off flavors as it's virtually impossible to disguise or tone down |
| Possible solutions | Allow yeast to do its "mop-up" job, control fermentation-chamber temperature, avoid using plastic |
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What You'll Learn
Plastic off-flavour in beer is hard to disguise
Plastic off-flavour in beer is one of the worst types of off-flavours in beer. This is because most off-flavours can be mellowed out, balanced, or even eliminated with countermeasures. However, plastic off-flavour is extremely challenging, if not impossible, to disguise or tone down.
Plastic off-flavour, also known as adhesive flavour, can originate from various sources, and it can be challenging to pinpoint the exact cause. In brewing, any plastic that comes into contact with heated water or wort can potentially contribute to this off-flavour. This includes items such as floating thermometers, garden hoses, and sanitizers. Even sanitizers may not be able to kill an infection embedded in plastic, making it difficult to prevent or eliminate the plastic taste.
Strawberry seeds, which contain high levels of p-coumaric acid, can also be a culprit. During fermentation, this acid can be biotransformed into compounds that taste like plastic. Additionally, certain strains of Brett, which is often used in brewing, can produce a band-aid flavour that is reminiscent of plastic.
Controlling the fermentation process and maintaining optimal temperatures are crucial to minimizing off-flavours. However, even with careful control, plastic off-flavour can still occur. In some cases, the off-flavour may become less noticeable over time, but it is challenging to completely eliminate it once it has developed.
To prevent plastic off-flavour, brewers must be vigilant about any plastic that comes into contact with their brew and experiment with different processes and ingredients to identify and eliminate potential sources of the off-flavour.
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Yeast can cause off-flavours
Yeast is often the number one culprit of off-flavours in beer. While yeast is primarily known for converting sugars to alcohol and carbon dioxide, it also produces hundreds of secondary metabolites, some of which can cause off-flavours.
Diacetyl is a buttery or butterscotch-like off-flavour that can be caused by several factors, including yeast. This flavour is commonly associated with lagers and English ales but can be found in any beer style. Diacetyl is a byproduct of yeast metabolism during fermentation. It is usually reabsorbed by the yeast cells, but non-reabsorption or overproduction can occur due to weak or short boiling, low fermentation temperatures, mutated yeast, or racking too soon. To prevent diacetyl, brewers should ensure their yeast is healthy and has sufficient nutrients, monitor fermentation temperatures, and avoid sudden drops or fluctuations.
Sulfur is another common off-flavour in beer that can be caused by yeast. Yeast produces sulfur compounds during fermentation as a byproduct of metabolism, resulting in a distinct aroma resembling rotten eggs or burnt matches. While small amounts of sulfur can be desirable in certain beer styles, excessive amounts can be unpleasant. To reduce sulfur production, brewers should match the FAN and nutrients in the wort to the yeast and ensure adequate nutrient supplementation, especially zinc, which plays a crucial role in yeast metabolism.
Phenols are a group of compounds that can give beer a range of off-flavours, including medicinal, band-aid, and clove-like flavours. These off-flavours are often produced by yeast during fermentation when exposed to chlorine in the water or in response to phenol precursors from malt or other ingredients. To prevent phenolic off-flavours, brewers should ensure healthy yeast with sufficient nutrients and avoid exposing yeast to chlorine or other halogens.
Yeast can also produce mercaptan, an off-flavour commonly caused by certain yeast strains, yeast autolysis, or infection by anaerobic bacteria. To avoid mercaptan, good sanitation practices are essential, and brewers should siphon their beer off the yeast within four weeks of fermentation start.
Additionally, yeast can cause an alcoholic off-flavour in beer, making a brew with a moderate alcohol level taste too boozy due to issues during fermentation.
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Plastic equipment can cause off-flavours
One theory is that the off-flavour is caused by phenolic contamination. Phenols are secondary metabolites with a hydroxyl group linked directly to a benzene ring, and they can come from a variety of sources, including yeast and grain. While yeast is typically the number one culprit of off-flavours in beer, plastic off-flavour may be caused by other factors.
Some brewers have reported that the plastic off-flavour only appeared after bottling, which could indicate a Brett infection. Some strains of Brett can produce a bandaid flavour that is similar to plastic. In addition, certain fruits, such as strawberry seeds, contain high levels of p-coumaric acid, which can be biotransformed by Brett into 4-vinylphenol and 4-ethylphenol, which taste like plastic.
To avoid plastic off-flavours, brewers should be cautious of any plastic equipment that comes into contact with the brew, especially if it has been heated. Glass equipment may be a better alternative, as it is transparent, allowing for observation of fermentation, and it does not carry the same risk of imparting a plastic flavour. However, glass vessels can be more expensive, heavier, and more difficult to clean than plastic ones.
Overall, brewers should be aware of the potential for plastic equipment to cause off-flavours in their beer and take the necessary precautions to avoid this, such as using alternative materials or ensuring that plastic equipment does not come into contact with heated liquids.
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Strawberry seeds can cause a plastic taste
Fermenting beer in plastic can sometimes result in an off-putting plastic taste. While the exact cause of this is unknown, it could be due to various factors such as high fermentation temperatures, wild yeast or bacterial infections, or the use of certain sanitizers.
Now, let's explore the claim that strawberry seeds can cause a plastic taste. It is important to understand the potential impact of strawberry seeds on the flavour of fermented beverages. Firstly, strawberries are commonly used in brewing, particularly for fruit beers and ciders, as evident from various online discussions and forums. Some brewers have reported experiencing a plastic taste in their strawberry-based brews. However, it is challenging to attribute this solely to strawberry seeds for several reasons.
Firstly, strawberries are typically washed, frozen, and pasteurized before being added to the brew, making it unlikely for the seeds to be the sole source of contamination. Secondly, in most cases, the entire strawberry, including the seeds, is consumed, and it is uncommon to isolate the seeds and add them separately to a brew. Therefore, if there were an issue with strawberry seeds causing a plastic taste, it would be more widespread and consistently reported.
Moreover, the potential for an off-taste in strawberry-based brews could be influenced by a variety of factors, including the type of yeast used, fermentation temperatures, and the presence of other ingredients or contaminants. In the case of a plastic taste, it is more likely to be caused by a wild yeast or bacterial infection, as mentioned earlier, rather than solely by strawberry seeds.
Additionally, it's important to consider the physiological effects of strawberry seeds. While they are generally safe to consume, some individuals may have an allergy or intolerance to strawberries, which includes the seeds. However, this would manifest as an upset stomach, stomach pain, inflammation, cramping, nausea, and other symptoms associated with allergic reactions, rather than a plastic taste. Therefore, while strawberry seeds themselves may not directly cause a plastic taste, the use of strawberries in brewing does require careful consideration and attention to sanitation to prevent unwanted flavours and potential health risks for consumers.
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High fermentation temperatures
Fermentation temperatures play a crucial role in the quality and taste of the final beer. While yeast is typically the primary culprit of off-flavours in beer, high fermentation temperatures can also negatively impact the beer's flavour.
Different strains of yeast have different "ideal temperature ranges" in which they provide the most desirable flavours. Ale yeast, for example, performs best in the upper 60s to low 70s (°F) range, while lager yeast generally performs optimally in the 48°F to 55°F range. Fermenting at too high a temperature can result in off-flavours, which can sometimes be quite severe. These off-flavours can be described as "hot" and create a burning sensation, such as the solvent-like nail polish flavour produced by English ale yeast at higher temperatures.
To avoid these undesirable flavours, brewers must control the fermentation temperature. This can be achieved through various methods, such as using a thermowell, a fermentation chiller, a converted refrigerator or freezer, or a temperature-controlled fermentor. The choice of yeast strain also plays a vital role in temperature control, with some strains, like Kveik yeast, being well-suited for warm temperatures with minimal off-flavours.
However, it's important to note that high fermentation temperatures are not always detrimental. In some cases, such as with saison-style beers, fermenting at higher temperatures can enhance desirable aromas, resulting in a fruity, floral, and bubblegum scent. Therefore, brewers must understand the stylistic accuracy of the beer they are aiming to produce and adjust their fermentation temperatures accordingly.
Additionally, it's worth mentioning that off-flavours in beer can also be caused by other factors besides yeast and fermentation temperatures. For instance, the use of plastic equipment during the brewing process can sometimes result in an unwanted plastic flavour in the beer, as some sanitizers may not eliminate all infections from plastic surfaces. Sparging, or rinsing off the mash grain bed, can also introduce tannins, leading to a plastic off-flavour.
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Frequently asked questions
The most likely cause of a plastic off-flavor in beer is chlorine, which may be present in your sanitizer solution. Even a slight hint of chlorine can be picked up and exacerbated by the other elements of your beer.
To prevent a plastic off-flavor in your beer, ensure that you thoroughly rinse out all of your brewing equipment each time you sanitize. You might also consider switching to a no-rinse sanitizer like Star-San or Iodophor. Additionally, make sure to keep your sanitation process thorough to avoid wild bacteria from getting into your beer and potentially causing plastic off-flavors, which are difficult to eliminate.
Off-flavors in beer can be caused by various factors, including high fermentation temperatures, oxidation issues, stale ingredients, bacterial contamination, and poor sanitation practices.
