Troubleshooting
The staff at The Brew Hut are always happy to try to diagnose any brewing or fermentation issues that you may encounter. You are always welcome to bring a small sample of your beer, wine, cider, or mead to the shop during regular business hours for an expert analysis.
Characteristics | Possible Cause | Possible Solution |
Butter, Butterscotch, Slick mouth feel | Diacetyl |
Diacetyl is a natural byproduct that is created during the fermentation process by brewers yeast as well as some select bacteria such as pediococcus. As yeast ferment sugars, they typically produce a large amount of diacetyl. As the yeast begin to complete the fermentation process, they will then absorb the diacetyl into their cell walls, thereby reducing it.
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Cardboard, oxidation, wet paper, sherry | Oxidized |
Papery flavor in beer is usually caused by the introduction of oxygen which can present itself as wet paper, cardboard or even sherry. Although oxygen is essential for good yeast health, when introduced after primary fermentation, it can quickly deteriorate and stale what would otherwise be a delicious beer.
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Corn, Creamed Corn, Cooked Vegetables | DMS (Dimethyl Sulfide) |
DMS or dimethyl sulfide is most often caused by the use of very pale malts such as Pilsner and 6-Row. During the germination process of barley, a compound called S-methylmethionine (SMM) is naturally produced. In most malts, this compound is driven off during the kilning process. But with lightly kilned malts such as pilsner, the SMM is kilned at lower temperatures and remains in the barley in high quantities. The DMS is then released through evaporation during an open, rolling boil. In cases where the boil vessel is left closed, or in the event that the wort is cooled very slowly the DMS can not be evaporated off and will be reabsorbed in the wort.
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Fruity (Banana, Pear, Apple, Strawberry) | Estery |
Esters are produced during fermentation by both ale and lager yeast.
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Green Apples | Acetaldehyde |
Acetaldehyde is a naturally forming byproduct in beer that is created during the fermentation process when the yeast is converting glucose to ethanol. In the event that the fermentation is poor because of unhealthy yeast, low pitch rate, or if the beer is transferred off of the yeast too early, the conversion of acetaldehyde to alcohol may not be complete, leaving a large amount in the final beer.
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Metal, Tin like, pennies, blood | Metallic |
Metallic flavors are most often caused by unprotected metals in contact with the wort,
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Mouth Puckering Astringency | Tannins |
Tannins are most often extracted from the malt during the mashing process. If the mashing temperature is too high (over 170 F) or the pH levels of the sparge water is over 5.8. They can also be extracted from the malt when sparging for too long.
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Plastic/ BAND-AID® | Chlorophenolic |
When a beer is high in phenolics (smoky, spiciness) and is brewed with water that is high in chlorine or chloramines, it can create a plastic flavor and aroma that is often described as Band-Aid® like or medicinal. Be sure to use water that has low chlorine or chloramine content and be sure to properly rinse any chlorine-based sanitizers.
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Skunky, Catty | Light Struck |
When hops are exposed to ultraviolet rays from the sun or fluorescent lighting, the alpha acids from hops break down and react with the hydrogen sulfide produced by the yeast. This reaction creates mercaptan. Mercaptan is the same chemical that skunks secrete when they spray, which is why the smell of lightstruck beer is so similar to that of a skunk.
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Smoky/ Spicy/Clove | Phenolic |
Most often phenols are derived from the yeast during fermentation. Some strains of yeast are more prolific at creating this spicy characteristic such as hefeweizen style strains and some belgian yeast strains. But even yeast that is not necessary prone to creating these spicy flavors can create phenols when stressed from under pitching or high fermentation temperatures. Other culprits include wild yeast and bacteria which can be controlled by maintaining good sanitation practices.
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Sour, Tart, Acidic | Bacterial Contamination |
Contamination is usually caused by the introduction of a bacteria. As there are many different bacterias that can infect a beer, they often present themselves in different ways. The most common bacterias found in beer are strains of lactobacillus and pediococcus. Both are members of the lactic acid bacteria (LAB) group. This means that they convert sugars into lactic acid.
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Sulfer, Rotten Eggs, Burnt matches | Hydrogen Sulfide |
Hydrogen sulfide is produced naturally by all yeast during fermentation. Lager yeasts tend to create greater sulfur aromas than ale strains. At low levels, it can impart a ‘fresh’ flavor to beers but at high concentrations it becomes an off flavor. CO2 will carry most of the hydrogen sulfide away and so conditioning or lagering after primary fermentation can ensure any left-over sulfur smells or tastes fade over time.
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Vinegar Like, Acidic | Acetic Acid |
Acetic Acid is produced by yeast in fermentation and is a natural byproduct of metabolism during the brewing process. But it can also be imparted by wild yeasts and bacteria such as Acetobacter (vinegar bacteria), a genus of aerobic bacteria that can turn ethanol into acetic acid during fermentation if excessively aerated.
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