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Aroma: Soapy, Rancid, or Fatty
A soapy, rancid or fatty aroma is a dependable but disappointing warning that your brewing process introduced an undesirable aspect into your beer. There are several potential causes and cures.
- Bacterial contamination can cause a rancid aroma.
- Caprylic or fatty acids, an intermediate by-product of fermentation, can cause a rancid aroma. These compounds are usually broken down by a healthy fermentation. Incomplete fermentation can be caused by insufficient aeration, lack of sufficient yeast, or an unhealthy and weak yeast strain.
- A soapy or rancid off-flavor may be a by-product of sanitation done poorly. The residue of sanitizing agents from improperly rinsed equipment can cause a soapy flavor or aroma in the beer.
- Maintain sanitary conditions.
- Ensure that fermentation goes to completion so that fatty acids can be converted to esters as desired. Ensure that the wort is aerated properly before the yeast is pitched. Prepare a yeast starter, especially for higher gravity worts, to ensure sufficient yeast is available at the time of pitching into the wort. Use a strong, healthy yeast strain that is suited to the style of beer being made.
- Thoroughly rinse brewing equipment after cleaning and sanitizing.