Brewing SolutionsThe Remedy of Flavours – Tips to Avoid Off-Flavours Part -1

All beers are made up of a complex array of flavours, and everyone perceives the various flavours differently. For instance, you may enjoy a particular brew, while your friend may detest it completely. We all have different sensitivities for various flavours and different preferences on what we like and what we abhor.

With that said, there’s a general set of flavours that are considered “off” by all. Some of these off flavours may be present in a brew, but only become “off” when their levels go high. Other off-flavours on the other hand, are not appropriate irrespective of their levels.

As a brewer, you need to recognize, identify, then eliminate these off-flavours from your brews. Honing this task doesn’t happen overnight – it takes plenty of practice. Here, in today’s post, we introduce you to the common off-flavours in your brews.

1. My beer smells buttery


Cause of Off-flavour: Diacetyl

How to Identify It? Your beer smells like buttery popcorn, or like butterscotch. Presence of buttery off-flavours makes the brew slick and creamy on your mouth and tongue. Very often known as the “original sin” of the brewer, diacetyl is mostly present in all beers but in low concentrations. Usually, a small amount of buttery flavour is tolerated in ales and stouts, but it is considered a brewing flaw in lagers.

How is it caused? Diacetyl occurs during the fermentation process. However, it is often reabsorbed by yeast. If the diacetyl is not re-absorbed completely, then it causes a buttery flavour. The reasons for this are mutated or weak yeast, low fermentation temperatures, problems with oxygenating or short boils.

2. My beer smells like Sweet Corn


Cause of Off-flavour: Dimethyl Sulphide

How to Identify It? This smells like cooked cabbage, sweet corn, shellfish, tomato sauce or even oysters.

How is it caused? This is the desired flavour in some ales and pale lager, while it’s an off-flavour in others. Certain compounds that are generated during the malting process are converted to Dimethyl Sulfide on heating. It’s mainly produced during wort production. DMS is more prevalent in lagers and pale ales and can also be caused by bacteria, present in the contaminated beer. To drive off this smell make sure that you boil the wort long enough to evaporate the DMS.

3. My beer has a Metallic Smell


Cause of Off-flavour: Ferrous Sulphate

How to Identify It? The beer smells like iron, blood, ink, pennies and other metals. Apart from the smell, you can easily taste the metallic tang on your mouth and teeth.

How is it caused? Ferrous Sulphate affects both the mouthfeel and the aroma of your brew. It occurs when the raw materials used in beer making come in contact with poor quality metal in your brewing equipment.

To avoid such problems with your brew, ensure that you use equipment of the finest quality from Microbrewery India.

4. My beer smells like Rotten Eggs


Cause of Off-flavour: Hydrogen Sulphide

How to Identify It? This one is easy to spot. You get a distinct smell of rotten eggs, boiled eggs, sewage or a burning match.

How is it caused? Hydrogen Sulfide is a byproduct of yeast fermentation and exists in all types of beers with varying concentrations. At low levels, H2S lends a “fresh” flavour to your brew, however, at higher concentrations, it lends an off-flavour. By conditioning or lagering your beer after the primary fermentation, it ensures that all leftover sulphur smells fade away.

5. My beer smells like a Ripe Banana

Cause of Off-flavour: Esters

How to Identify It? Mostly the beer smells like a ripe banana or a pear. At times, it may smell like grapefruit, raspberry, or strawberry.

How is it caused? Isoamyl acetate is a common ester that is a key flavour in German-style wheat beers, lagers, and Belgian ales. This is a natural by-product of fermentation. However, if your beer has strong fruity flavours, then it means there is something wrong with your fermentation temperature – you are either under pitching or high pitching it. The higher the fermentation temperature, the more esters are present in your brew. Try to control fermentation at the right levels to avoid this off-flavour.

6. My Beer smells like Paper

Cause of Off-flavour: Oxidised (trans-2-noneal)

How to Identify It? This off-flavour smells like wet paper, cardboard or a dry sherry taste.

How is it caused? This is a characteristic flavour usually found in ageing beers. This flavour is likely to be present when oxidation happens without any control. Oxidation happens when oxygen reacts with the wort or brew. However, oxidation is a bit difficult to control.  You can avoid extra oxidation by reducing the headspace in your beer bottle and avoiding unnecessary splashing of fermented beer while moving it from one vessel to another.

7. My beer smells Musty

Cause of Off-flavour: Trichloroanisole

How to Identify It? You can identify the presence of TCA if your beer smells like a damp cellar and mould.

How is it caused? TCA is usually caused when the fermentation occurs in a damp space. To avoid this, ensure that your brewing area is moisture-free and doesn’t have high humidity levels.

8. My beer smells like Cloves

Cause of Off-flavour: Phenols

How to Identify It? This one tastes like cloves, but at times, the aroma can be similar to spices, herbs, smoke or cough syrup.

How is it caused? Phenolic flavours are key flavours in certain types of beers like ales, stouts, and German-style wheat beers. However, in all other types of beers, it’s an off-flavour. This is a result of the presence of wild yeast strains during fermentation. Additionally, phenolic flavours also occur due to poor hygiene (improper cleaning of your brewing equipment) and contamination of raw materials.

9. My beer smells like Green Apples

Cause of Off-flavour: Acetaldehyde

How to Identify It? Look for the smell of rotten apples, green apples, freshly cut pumpkin or emulsion paints.

How is it caused? Acetaldehyde is generally produced during fermentation. It’s usually converted into Ethanol alcohol. When this process is incomplete, it gives an apple flavour. Reasons for this are low fermentation time, reduced yeast quantity or poor quality of yeast.

10. My beer smells like Baby Vomit

Cause of Off-flavour: Butyric acid

How to Identify It? You can easily identify this flavour as it’s quite off-putting. Look for a rancid or putrid smell like baby sick.

How is it caused? This is an off-flavour in all styles of beers. This is mainly caused by the presence of bacteria during the wort production phase. Ensure that your brew is free from bacterial contamination during this stage.

These are the 10 common types of off-flavours, you are likely to come across while brewing. Stay tuned for our next post in this series for additional tips and brewing guidelines on how to avoid these off-flavours in your brews. Rohit Jafa has the best flavour beer brewing in India.