Various things can go wrong with the flavor of homebrewed beer, and it’s easy to be at a loss for what might have caused your beer to go off. If your brew tastes
The most common causes of chemical off-flavors are heightened chlorine levels or bacteria and wild yeast in your brew. Secondary causes can be extended dry-hopping or elevated fermentation temperature. If your finished brew has chemical off-flavors, you are better off trying again as they often result from processes that are irreversible later.
Please keep reading to learn what might cause a chemical taste in your homebrew and what to do about it.
What causes a chemical taste in homebrew beer?
If your beer tastes “chemical,” it helps first to identify the type of taste.
Most commonly, your brew tastes of plastic or antiseptic. In this case, phenols and chlorine are likely culprits.
There are a variety of phenol compounds, some of which are welcome in beer. A phenolic compound contains hydroxyl (OH) and an aromatic hydrocarbon ring. All beers contain some types of phenols. For instance, polyphenols, like tannins, result from hops and malt. Low levels can contribute to a pleasant mouthfeel, like in Hefeweizen.
High levels of phenols, however, promote dry, astringent flavors.
There are three sources of phenols: ingredients, chemicals, and bacteria or (wild) yeast.
Our handy Oxford Companion to Beer provides a solid example of “good” phenols:
Rauchmalt, translated as “smoke(d) malt,” or malt dried over an open fire with beechwood, is a specialty from Bavaria, Germany. Rauchmalt adds guaiacol and syringol, resulting in a smoky aroma and taste. These phenols create the distinct profile of rauchbier (smoked beer).
On the flip side, chemicals, namely chlorine and chloramine, combine with phenols to create chlorophenols, which are “bad” phenols.
Potable water is usually suitable for brewing but may require some adjustments.
Certain chemical compounds, including chlorine and chloramine, present in tap water can influence the resulting taste of your beer. Understanding the quantity of these in your water will help you to avoid unwanted off-flavors.
Chlorine and chloramines are commonly added to public water sources to keep harmful bacteria out. A small amount can influence malt sweetness, but too much can result in chemical off-flavors.
Chlorine reacts with yeast-derived phenols, creating chlorophenols, which cause plastic off-flavors. Water with a higher chlorine concentration is more likely to produce more chlorophenols during fermentation, thereby increasing these unwanted flavors.
Bacteria or Wild Yeast
Ineffective sanitization can give way to bacteria and wild yeast, which further contribute to off-flavors. Although sanitizers, like Star San, are effective, no-rinse methods, some yeast and bacteria strains still prevail.
Bacteria and wild yeasts can contribute to an array of off-flavors, including chemicals.
Some bacteria can spoil wort, which negatively impacts the aroma and flavor of your beer, even before fermentation. According to the work of Dwight B. West, Albert F. Lautenbach, Donald D. Brumsted, some gram-negative, indole-negative, short-rod, wort spoilage bacteria can produce medicinal or “phenolic” flavors in beer.
Over-Extraction of Hops
Dry hopping is the process of adding hops, commonly in secondary fermentation. This process adds more hop flavor and aroma to your beer. India Pale Ale (IPA) is a popular style that commonly includes dry hopping.
The hops are added after boiling to minimize oil extraction, which contributes to bitterness. However, there is a large amount of chlorophyll in plants.
When left in the beer for over a week, the plant material can cause plant or medicinal flavors in your beer. Note, this situation more commonly causes plant-like (more medicinal than chemical) off-flavors.
For the science buffs:
In a study by Thomas H. Shellhammer, and Cindy Lederer, Ian R. McLaughlin, the authors studied how polyphenolic bitterness influences beer flavor when combined with iso-α-acid. They found that when polyphenols and iso-α-acids both increase, the beer’s bitterness becomes harsh, medicinal, or metallic. This result suggests that a high quantity of polyphenol, resulting from prolonged dry-hopping, likely induces these unwanted off-flavors.
High Fermentation Temperature
If the chemical off-flavor resembles a solvent, like paint thinner, the fermentation temperature was probably too hot.
High temperatures stimulate higher yeast metabolism, causing it to produce acetate esters. These esters are in the same family as some industrial chemicals, such as paint thinner and nail polish remover.
How do you get rid of a chemical taste in homebrew beer?
If your brew has a chemical or plastic taste, unfortunately, you probably need to start fresh.
These off-flavors result during brewing or fermentation, as noted before. Unlike yeasty off-flavors, some of which can be resolved by secondary fermentation or filtering, these methods would likely worsen the chemical flavor.
How to prevent chemical flavors in your next batch of homebrew beer
Even though this brew may be a loss, there are ways to ensure you don’t have the same problem next time.
Instead of lamenting the result, take these steps to avoid chemical off-flavors in your next brew:
- Test and treat your water for chlorine to keep it at a minimum in your brewing water.
- Before starting on your brew, make sure to sanitize properly!
- Finally, during fermentation, pay attention to the recommended temperature range in your recipe. Fluctuations can cause unwanted effects in your brew. In the same vein, tmove and transfer your brew carefully, when necessary, to avoid over-oxidation.
Moderate Chlorine Amount
To determine the amount of chlorine in your brewing water, you can use a home kit, such as this one by VARIFY Store or this one by Hofun. These kits provide you with more insights than just chlorine, which can be useful in determining other off-flavors. Alternatively, you can request a comprehensive report from your municipal water treatment source.
To remove excess chlorine from your brewing water, boil it before brewing. If you plan to brew tomorrow, just the water uncovered overnight. In both cases, the chlorine will dissipate into the air.
Chloramine is more challenging to remove from tap water. Campden tablets, composed of potassium metabisulfite or sodium metabisulphite, hit two brews with one stone. These are available online or at your local brewing supplies store. These tablets contain sulfur dioxide, which cleans out chlorine and chloramines from the water. You only need a piece since a standard tablet treats up to 75 liters of water.
If you use sanitizer with chlorine, such as bleach, make sure to rinse your equipment thoroughly. I recommend switching to Star San, a popular no-rinse sanitizer.
Sanitization is a crucial step in the brewing process.
To minimize the risk of contamination, make sure to sanitize each piece of equipment, not just the fermentation vessel. A little (more) attention goes a long way! Consider replacing old plastic pieces after prolonged use.
In addition, minimize the exposure of your brew to open-air throughout the process.
Control Fermentation Temperature
If you suspect that the chemical flavor resembles a solvent, watch the fermentation temperature in your next batch.
Fermenting at the lower end of the suggested range decreases resulting acetate esters but lowers attenuation.
I recommend pitching at the low end, then allowing fermentation to warm up over the next few days.
Over-oxidation can sometimes contribute to solvent-type flavors.
Move your beer carefully, whether to your fermentation corner or when transferring to the secondary vessel.
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