Mousiness in wine: An old challenge resurfaces – and how qPCR can help

Mousiness (or mousy taint) is making a comeback. Long considered a niche fault associated with natural or low-intervention winemaking, this off-flavor is increasingly being reported in a wider range of wines – including conventional styles. For wineries and labs alike, it presents both a sensory and microbiological challenge. Fortunately, modern tools like real-time PCR can bring clarity and control to an otherwise elusive defect.

What is mousiness?

It is a wine fault that produces an unpleasant mouse cage or nutty-metallic smell and taste. What makes it especially frustrating is its delayed perception: the taint often appears only after swallowing, and usually takes a few seconds to build, making it difficult to detect during standard tastings.

The substances responsible for ‘mousiness’ are the N-heterocyclic volatile bases 2-acetyltetrahydropyridine (ACTPY), which is the main compound responsible, 2-ethyltetrahydropyridine (ETPY) and 2-acetylpyrroline (ACPY). These compounds are not volatile under acidic pH and only become perceptible in the mouth when pH rises. This makes detection subjective and heavily influenced by the taster’s sensitivity.

Who (or what) causes it?

Mouse taint is primarily linked to certain lactic acid bacteria (LAB), especially strains of Lactobacillus hilgardii, Oenococcus oeni, and Pediococcus. Some strains of Dekkera/Brettanomyces may also contribute.

The formation of the taint depends on several factors, such as:

• High pH values
• Low sulfur dioxide (SO₂) levels
• Exposure to air / oxygen
• Minimal clarification or filtration
• Amino acid profiles in the wine (especially lysine)

Why is it on the rise again?

The resurgence of mouse taint is tied to several trends in modern winemaking:

• The increasing popularity of natural and low-intervention wines, often with minimal SO₂ and filtration.
• Warmer vintages, leading to higher pH wines, which promote LAB growth and mouse taint perception.
• Changes in wine microbiota due to climate, winery hygiene, and equipment reuse.

As winemakers push boundaries on style and fermentation, the microbial ecosystem becomes more complex — and sometimes unpredictable.

How Real-Time PCR Can Help

Mousiness must be proactively and preventively managed during the production process, as it cannot be removed by fining. Traditional detection methods (e.g., culture-based or sensory) are often too slow or unreliable. This is where real-time PCR shines.

Our GEN-IAL real-time PCR kits allow:

• Fast and specific detection of key spoilage organisms like Lactobacillus spp., Pediococcus spp., and Brettanomyces / Dekkera
• Multiplex kits are available for simultaneous detection of multiple spoilage organisms in a single test – ideal for use during MLF monitoring, cellar hygiene checks, or problem-solving in bottled wines
• Quantification of Dekkera bruxellensis to assess risk levels
• Support for preventive decisions before bottling or during barrel aging

Be Proactive, Not Reactive

Whether you’re producing classic varietals or natural wines, early detection and microbial monitoring are key to managing wine faults like mouse taint. With the right tools, including our GEN-IAL qPCR kits, wineries and labs can take control and ensure sensory integrity — bottle after bottle.

For more information or to request a demo, contact info@r-biopharm.de
or visit https://food.r-biopharm.com/industries/wine-analysis/