All beers are different, as no two use the same combination of hops, malts, water, yeast, and other ingredients in the brewing process. Training your palate is essential, since it will help you detect any potential anomalies in a beer. This guide will help you identify and understand off-flavours in beer, so you can achieve the ideal aromatic balance in your brews.
Biological factors
When tasting beer, you may sometimes notice a strange, indefinable flavour. Here’s where these off-flavours come from and how to avoid them.
Apple flavour
This apple-like taste is caused by acetaldehyde, a chemical compound naturally produced during fermentation. It can give aromas reminiscent of rosemary, mint, bitter orange, or fennel. Its presence usually results from adding too much sugar to the wort, maintaining an alcoholic fermentation temperature that is too high, or shortening fermentation time.
Strong alcohol taste
If your beer has an overwhelming alcohol flavour, the causes may be:
- Excessive yeast concentration.
- Primary fermentation above 27°C, which increases alcohol release.
To fix this, keep fermentation temperature stable as per the recipe and ensure a proper yeast inoculation rate at the start.
Rancid butter flavour
Notes of rancid butter, cheese, or sweat are caused by diacetyl, released by yeast early in fermentation. To prevent this, keep the pH between 5.0 and 5.2 at the start, finishing between 3.8 and 4.4. Allow the temperature to rise slightly for 1–2 days at the end of fermentation, and ensure sufficient oxygen at the beginning so yeast multiplies effectively. If diacetyl persists, cold-store the beer for 2–4 weeks, ideally after bottling to avoid oxidation.
Cooked vegetable flavour
The compound responsible here is dimethyl sulphide (DMS), which can produce aromas of corn, cabbage, or beetroot. It often appears in bottom-fermented lagers due to the malting and boiling stages. To minimise DMS, avoid covering the boiling vessel and cool the wort quickly using a coil, as DMS is volatile.
Medicinal taste
This flavour is caused by chlorophenols, formed when chlorine in tap water reacts with phenols from yeast. Always boil tap water before brewing to remove chlorine, treat it with potassium metabisulphite, or use spring water instead.
Off-flavours caused by physical factors
Light flavour
Beer is highly sensitive to light. If stored in clear bottles, UV rays break down hop compounds, creating a sulphurous, “skunky” flavour. Use dark or opaque bottles to protect your beer.
Cardboard taste
This flavour comes from oxidation of the wort or beer. Avoid splashing during transfers, limit exposure to air, and keep headspace in bottles minimal. Proper bottling and gentle brewing techniques are key to reducing oxidation.
Now that you know how to recognise and correct these off-flavours, you’ll be better equipped to troubleshoot your brewing process. With practice and attention to detail, you’re on the right path to becoming a true expert in homebrewing and beer tasting.
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