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Why does the Summer Season Pose Unique Challenges for Beer Quality

Summer is peak beer season, but it’s also peak risk season for beer quality. Warmer temperatures can accelerate chemical reactions and microbiological spoilage, leading to undesirable flavours in packaged or draft beer.

Whether you’re a brewer, QA professional, or work in distribution, understanding summer-specific off-flavours is essential for ensuring every pint poured meets your brand’s quality promise.

In this blog we will highlight some of the most significant and unpleasant flavours to look out for.

1. Lightstruck (Skunky)
Cause: UV light exposure, especially in clear or green glass bottles
Flavour profile: Skunky, sulphuric, reminiscent of rubber
Risk level in summer: High – increased sunlight and outdoor consumption
How it happens: UV light breaks down hop-derived isohumulones, forming 3-methyl-2-butene-1-thiol (MBT). This compound is detectable in parts per trillion, meaning even brief light exposure can ruin a beer.
Prevention:
• Use amber glass or cans
• Educate retail staff and consumers on storage
• Conduct lightstruck detection training for your panel

2. Oxidised
Cause: Oxygen ingress + heat exposure
Flavour profile: Stale, cardboard, wet paper, or sherry-like in darker beers
Risk level in summer: High – accelerated by higher storage temps
Oxidation is a slow killer. While oxygen pickup can happen during packaging, heat amplifies its effects dramatically, especially if the cold chain is broken during transport or storage.
Prevention:
• Monitor dissolved oxygen (DO) levels in production
• Educate distributors on temperature control
• Train tasters to detect early-stage oxidation

3. Diacetyl
Cause: Incomplete fermentation or bacterial contamination
Flavour profile: Buttery, popcorn, slick mouthfeel
Risk level in summer: Moderate – more prevalent with fermentation stress
Warmer temperatures can cause unpredictable yeast behaviour if sanitation is lacking. Diacetyl is especially problematic in beers with fruity profiles, where it can mask or clash with natural esters.
Prevention:
• Ensure complete fermentation and perform VDK tests
• Maintain tight sanitation control in packaging
• Run diacetyl flavour standards in your training program

4. Acetic (Vinegar)
Cause: Wild yeasts or bacteria (e.g. Acetobacter)
Flavour profile: Vinegar, sour, solvent-like, or ethyl acetate (nail polish)
Risk level in summer: Moderate – exacerbated by warm, humid conditions
In the summer, wild microbes thrive. This can especially affect small breweries or venues with open tanks or variable sanitation protocols.
Prevention:
• Monitor for contaminants via microbiological testing
• Use sensory panels to catch subtle sour or solventy notes early
• Ensure beer lines are cleaned more frequently in hot weather

5. Metallic
Cause: Poor packaging materials, rust, or damp storage areas
Flavour profile: Blood-like, tinny
Risk level in summer: Moderate – linked to poor warehouse conditions
Humidity and fluctuating temperatures can affect packaging integrity, leading to leaching of compounds or microbial growth on packaging surfaces.
Prevention:
• Inspect packaging conditions in warehouses and transit routes
• Conduct regular quality audits
• Include metallic compounds in staff sensory training

How Sensory Training Can Help You Stay Ahead

Spoilage doesn’t always scream; it can be more difficult to detect- especially when you’re not sure what you’re looking for. A trained panel can detect spoilage compounds long before customers complain.

FlavorActiV offers GMP Pharma-grade flavour standards for off flavour detection. Our Flavour Standards underpin panel management and training and the development of custom programs for breweries and beverage production.

Key Takeaways
• Summer heat increases the risk of several spoilage off-flavours
• Lightstruck and oxidation are particularly problematic this season
• Microbial spoilage, poor storage, and packaging integrity are amplified

Ready to Strengthen Your Sensory Defences?

Explore our beer flavour standards and sensory training solutions, trusted by breweries worldwide.
Contact us today or explore out flavour kits here!