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What's that funky smell?

Last winter our wine sales decreased a lot, partly because of the C-word but also because many people decided to partake in ‘Dry January’. I suspect January and February 2022 will be a similar outcome so, as few people are likely to drink alcohol this month, I decided to write about the defects of wine and how to recognise them.

A sommelier checking the quality of a wine

At the end of the day, there are a great many aromas and tastes that we all enjoy when we drink a glass of wine, but unfortunately, there are also many defects and they can be hard to detect.

Many people have happily finished a bottle of defective wine without ever knowing there was a problem with it. 

In all my years of service, I have opened my fair share of bottles.

Incredibly, the number of bottles that clients have rejected due to defects is approximately 1% or less, whereas the bottles I have flagged as corked or having other defects are more than 2-3%. Professionals are trained to detect the most basic faults in wine, so it is important to let yourself be guided by them and their experience.

If you think your wine has a funky smell, don’t be shy, ask the professionals for their opinion.

At the very least, they should listen to what you have to say and then smell or taste the wine to give their point of view. In any case, they should also change the wine if you are not happy with it.

Some defects are easier to spot than others, and they can also have different levels of development. There will be times when the smell of corked wine is noticeable as soon as you open the bottle and other times, the smell appears after 30 minutes or so. Or some of the bacteria that spoil the wine may not be fully developed by the time you open the bottle so you may not always be able to detect it.

Here is a list of the most common problems you might find and how to identify them:

Corked wine defects

Corked Wine

Most of us have come across a corked wine bottle in our lifetime. Generally it smells of humidity, wet cardboard, or in some cases, the smell is like mushroom or wet soil. The aroma is caused by a chemical compound called 2,4,6-Trichloroanisole or TCA. It is a mix of fungi that is naturally present on tree bark and some chlorinated compounds that are used during the processing and disinfecting of the bark itself. Some of us can recognise the smell from across the room while other people aren’t aware of it at all. If you think your wine is corked, seal the remainder of the bottle with its original cork and take it back to the shop you bought it from. Wineries know there is a good chance this can happen, so they will reimburse the retailer for any corked bottles.

Volatile acidity defects

Volatile Acidity (VA)

This defect was not much of a problem in the past, however, with the rise of natural or minimal intervention wines, volatile acidity can now be found in some of these particular wines due to the less aggressive winemaking preservation techniques. The VA can be identified as the smell of nail polish remover, paint thinner, or in some cases, just vinegar. During the fermenting and aging processes, the natural evolution of wine is to become vinegar.

Therefore, the winemaker must halt this evolution to ensure the grape juice tastes amazing instead. Some winemakers use chemicals, such as sulphites, to halt this process and others prefer not to. The winemakers who are keen to create a wine without the use of these particular chemicals have more risk of bacteria development, which sometimes results in undesirable smells or ruined wine.

Oxidation defects


Oxidation is caused by oxygen. As well as being a great way to 'open up' or let your wine breathe, oxygen can also be a wine's enemy. Small amounts of oxygen given at the right time make aging and other processes beneficial. However, if too much oxygen makes its way into a bottle, a barrel, or a vat, the result is problematic. An oxidised wine is brown, without any lustre, and with little or no fruit aromas. The wine will also taste dry and bitter.

Brettanomyces (aka Brett) defects

Brettanomyces aka Brett

Brettanomyces (or Brett) is a type of yeast found in wine and beer making. Some beer styles rely on this yeast to be present to add bitterness and character, but the levels in wine must be low or they can be very unpleasant.

There are some Californian wines with low levels of Brett and in this case, they are considered to add personality to the wine. Brett can come from several situations including the grapes themselves, so it's nearly impossible to eradicate. However, what the winemakers can do is lower the impact of Brett in their wines. The aromas of Brett have many descriptions, but the most common (and least offensive ones) are leather, animal, farmyard, or manure.

Mousiness defects


This is possibly the hardest fault to describe. It appears randomly in some bottles of natural wines. In the glass the wine may smell fine, however, when you taste and swallow it, you may be aware of the flavours of mouse cage, water biscuits, rice, or popcorn. This phenomenon, and the random way in which it appears, has had little study. It can eventually disappear or get worse over time. It can also develop during any stage of the winemaking process, so you could potentially have a mousey barrel, vat, or bottle. 

We all want to enjoy that perfect bottle of wine, but if you do come across a defective bottle don't just discard it, try to analyse what is wrong with it so that you can become more familiar with wine taints or faults.

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