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Off Flavours in Beer and How to Identify Them

Updated: Dec 8, 2020

Whether you’ve got a few brews under your belt already or you’re just starting out, one of the most important tasks you need to master as a home brewer is that of identifying when a beer you have brewed is off. It’s easy to tell whether a brew is pleasing to your palate but how can you tell the difference between a batch you’re simply not keen on and one where something went seriously wrong? In all honesty, it’s a skill that can only be developed with practice but the tips below should give you a head start. Common Off Flavours in Beer: How to Spot Them and What to Do About Them Off flavours can arise from issues with either the brewing or the bottling/packaging process. In this article, we’re going to focus on those undesirable flavours that are caused by issues with the brewing process.

Dimethyl Sulfide – If you notice an unpleasant boiled vegetable flavour in your beer, perhaps like cabbage or stewed tomato, dimethyl sulfide is the most likely culprit. This chemical develops in the wort at high temperatures and is present in small quantities in all beer. An excess of dimethyl sulfidemay be caused by poor yeast health or by covering your brew kettle when boiling the wort. Uncovered boiling will get rid of most of it, as will vigorous fermentation. It is a common problem when brewing pilsner and pale malt beers, which you can solve with a longer, uncovered boiling period and by using fresh yeast. Acetaldehyde – This chemical is produced as the yeast in your brew is ridding itself of CO2. Under normal brewing conditions, most of the acetaldehyde should be consumed by the yeast and converted into alcohol but if you rush the fermentation process, too much of it can be left. This results in a noticeable off flavour in your beer that many have likened to wet grass or green apples. Diacetyl – During fermentation, a chemical process known as amino acid synthesis causes diacetyl to leak from yeast cells. If you let your beer rest for long enough, the diacetyl should be reabsorbed by the yeast. However, if you try to hurry things by skipping this rest period, a buttery popcorn taste and a slick feel in the mouth could be the result. The solution, as with acetaldehyde issues, is not to rush your brewing. Ethyl Acetate – Ethyl acetate presents with a fruity aroma at lower concentrations: a desirable quality in certain Belgian brews. However, at higher concentrations it causes a harsh solvent flavour like nail polish remover.The primary cause of high ethyl acetate levels in beer is allowing the temperature to get too high during the fermentation period. You’ll find these off flavours easier to spot as you gain experience but if you run across any unusual tastes that you can’t identify, feel free to get in touch and we’ll do our best to help.

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