BLOG

Understanding and Preventing Off-Flavours in Wine
Off-flavours in wine are one of the most frustrating challenges winemakers face, threatening to undermine the artistry and precision of their craft. These undesirable tastes and aromas can originate at any stage of wine production, from grape cultivation to bottling. Whether it’s sulphurous notes, oxidation, or microbial contamination, off-flavours can detract from the intended sensory profile, rendering the wine unpleasant or undrinkable. Understanding these faults, their causes, and how to prevent them is essential to ensuring high-quality wine that consumers can enjoy with every sip.

What are Off-Flavours?
Off-flavours are sensory defects or taints in wines that are unpleasant or atypical and thus take away from the desirable profile of the wine. Off-flavour may come from any stage of wine production, from the grape growing process to fermenting or even ageing. These unwanted flavours may result from subtle faults and overpowering flaws that may even make the wine undrinkable. Some common off-flavours include sulphur compounds, oxidation, volatile acidity or microbial spoilage. Each of these has a unique cause and can significantly decrease the wine quality.

Off flavours not only affect the aroma and taste but also make it unmarketable. The most minor defects may lead to poor reviews from both critics and consumers, affecting the reputation of the winery and its sales.

Common Causes of Off-Flavours in Wine
1. Sulphur Compounds (Reduction): Often described as reductive off-flavours, they can make wine emit an unpleasant aroma that may resemble rotten eggs, garlic, or even burnt rubber. These occur due to a lack of sufficient oxygen during fermentation or ageing, which may cause sulphur-containing compounds such as hydrogen sulphide to accumulate.
Reduction may be caused due to improper fermentation practices. Stress on yeast due to nutrient deficiency or excess of sulphur dioxide additions may lead to the wine developing notes of sulphur. The use of sulphur in the winemaking process is common and requires employing delicacy, as it is a common preservative, but its misuse can lead to it becoming off-flavour.

2. Oxidation: Oxidation of wine may also lead to off flavours in it. On being exposed to oxygen, the wine can lose its freshness, which may lead to it becoming flat and lifeless. Oxidised wines will often be brownish and develop sherry or nutty flavours, which are considered undesirable in most wine styles. It may have been caused due to poor storage or improper sealing of the wine during bottling. Wines need to be stored properly, away from excessive heat and light, and sealed tightly to prevent oxygen ingress. If oxidation begins in the wine, it is difficult to reverse, which is why preventive measures are critical.

3. Volatile Acidity: Acidity in wines is a result of acetic acid or ethyl acetate, giving the wine a sharp, vinegar-like taste and aroma. Although small amounts of volatile acidity is present in all wines naturally, if it reaches a certain acceptable threshold, it may result in overpowering sourness masking the true character of the wine.
It often arises due to bacterial spoilage of the wine, especially due to the presence of Acetobacter in the wine. Poor sanitation practices in the winery, along with excessive oxygen exposure during fermentation or ageing, may lead to even more volatile acidity.

4. Microbial Spoilage: Unwanted microbes in the wine or even wild yeast can also introduce off-flavours in the winemaking process. Brettanomyces is a type of wild yeast known for producing barnyard-like, medicinal or smoky flavour. Some old-world reds and other wine styles may tolerate a small amount of these yeasts, but excessive levels of this wild yeast are a flaw.
Other microbial spoilage issues may result from lactic acid bacteria resulting in mousy or cheesy off flavours, that may make the wine undrinkable. Good winery hygiene, a controlled environment for fermentation and proper use of sulphites are the key to preventing this microbial contamination.

Preventing Off-Flavours in Wine
The wine’s off flavours can be prevented by controlling a variety of factors such as careful vineyard management, precise winemaking practices and stringent quality control measures employed throughout the wine production process.

1. Grape Quality and Harvesting: The production of high-quality wine starts from producing high-quality grapes. The vineyard needs to be carefully managed; whether it is in regards to controlling pests, diseases, or vine stress, it is essential to produce grapes free from faults. The harvesting time is critical as well, overripe or underripe grapes may lead to off flavours such as excessive sweetness or green notes vegetal in nature.

2. Proper Fermentation Techniques: The yeast health also needs to be noted to prevent off-flavours during fermentation. It can be managed by providing yeasts with adequate nutrients, ensuring a smooth fermentation process, and reducing the risk of sulphurous compounds and volatile acidity development. Temperature needs to be controlled to avoid the stress on yeasts, and to not make it overwhelmed. This helps avoid the fermentation-related defects.
It is important the appropriate strain of yeast is chosen to achieve the desired wine style, minimise microbe spoilage, and prevent the development of off-flavours.

3. Oxygen Management: Oxygen can either aid or disrupt the winemaking process. Certain wines, like the reds, benefit from controlled exposure to oxygen, as it softens the tannins. Too much oxygen, on the other hand, may lead to premature oxidation. Oxygen exposure needs to be managed at every stage of the production, whether it be fermentation or bottling, as it is the key to preserving the freshness of the wine and preventing oxidative faults. By using inert gases, like nitrogen or argon, while bottling or ageing, the wine can help displace oxygen, hence reducing the risk of oxidation. Proper closure selection, such as high-quality corks or screw caps to seal the bottle, also help prevent oxygen ingress during storage.

4. Sanitation and Hygiene: Keeping the wine production environment sterile is crucial to making sure that the wine is not contaminated by microbes. From tanks to barrels, all the equipment needs to be thoroughly cleaned and sanitised after being used to prevent unwanted bacteria and yeast from growing. Sulphur dioxide levels also need to be maintained and monitored continuously, while a filtration system keeps the wine safe from microbial contamination.

5. Sensory Evaluation and Testing: The final safeguard against off-flavours is sensory evaluation before the wine makes its way to the market shelves. Trained sensory panels help detect subtle flaws which might have been missed in the production process, allowing the winemakers to take corrective action before bottling the wine. By making use of these regular sensory testing and quality control checks throughout the production process, winemakers ensure that off-flavours can be identified and addressed as early as possible.

Conclusion
While the wine’s off-flavours can be a huge difficulty for winemakers, preventive measures can be employed to safeguard the quality of the final product by understanding its causes. It might be managing the quality of the grapes, maintaining a hygienic winery, or even the oxygen exposure of the wine; these off-flavours can be prevented by observing the details at each stage of wine production meticulously. By carefully observing the sensory evaluation and quality control, winemakers can ensure their wines meet the highest sensory standards, keeping it free of undesirable taste and aroma.

Don’t let off-flavours affect the quality of your wine. Discover FlavorActiV’s sensory training solutions, which help you detect and prevent defects in your product and elevate the sensory profile of your wine.