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Band-aid flavor (phenols)
The band-aid flavor is usually caused by a reaction of phenols with chlorine. Chlorophenols are created when phenols react with chlorine from bleach or other chlorine-based cleaners. These molecules can affect the taste in single parts per billion – tiny amounts can ruin the flavor of your beer.
If your beer has the dreaded band-aid flavor, you are introducing chlorine into your beer at some point in your process. The chlorine can come from you city’s tap water or possibly your cleaning solution. If you are using a chlorine-based cleaner, make sure you rinse your equipment thoroughly with boiled water. A better solution is to never use chlorine to clean your equipment.
Some wild yeast can produce this flavor, but it is more likely the problem is coming from chlorine. If you are practicing good sanitation techniques, the first step to correct this problem is to eliminate every possible source of chlorine. Make sure your sanitizers are not using chlorine and use filtered water.
* Chlorine-based sanitizers mixed with phenols produced by fermentation
* Some yeast strains, such a Bavarian, will produce some clove-like phenol flavors which are desired
* Too much chlorine in your city water can give this flavor
* Don’t use chlorine, instead opt for a no-rinse sanitizer like StarSan