Isovaleric Acid Flavour Standard

WHAT IS ISOVALERIC ACID FLAVOUR?
Isovaleric acid is a naturally occurring organic compound found in various foods and beverages, particularly hop-based alcoholic drinks like beer. While it serves as a flavouring compound in some contexts, it is widely considered an off-flavour in most beer styles, especially non-sour beers.

In certain strong hoppy craft beers, a subtle amount of isovaleric acid may contribute a slight cheese-like note, which can be acceptable within style guidelines. However, excessive levels typically indicate quality issues.

Flavour Threshold: 0.5 – 2 mg/l

WHAT CAUSES ISOVALERIC ACID OFF-FLAVOUR?
Isovaleric acid off-flavour in beer arises from several brewing-related factors:

• Old or degraded hops: Oxidised or improperly stored hops release isovaleric acid during brewing
• High hopping rates: Excessive hop usage, especially in heavily hopped craft beers, can introduce elevated isovaleric acid levels
• Poor hop storage conditions: Exposure to heat, light, or oxygen accelerates hop degradation
• Extended aging: Prolonged storage of hop-forward beers can lead to isovaleric acid development

USING THE ISOVALERIC ACID FLAVOUR STANDARD FOR SENSORY TRAINING
The FlavorActiV Isovaleric Acid Flavour Standard provides a controlled, reproducible reference for training professional tasters, brewers, and quality control teams.

Training Applications:

• Threshold detection: Teach tasters to identify isovaleric acid at various concentration levels
• Flavour intensity assessment: Calibrate sensory panels to rate potency accurately
• Quality benchmarking: Establish acceptable limits for different beer styles
• Consistency training: Ensure uniform sensory evaluation across teams and locations

This standard is particularly valuable for breweries producing hop-forward styles where distinguishing between desirable hop character and off-flavours is critical.

HOW TO RECOGNISE ISOVALERIC ACID FLAVOUR: SENSORY TERMS
Key Sensory Descriptors:

• Stale cheese – reminiscent of aged or spoiled dairy
• Sweaty – body odor-like, rancid notes
• Old hops – oxidised, degraded hop character
• Putrid – sour, decaying organic matter

Training with the isovaleric acid flavour standard helps tasters develop a sensory memory for these characteristics, enabling rapid and accurate identification during quality assessments.

WHAT ARE THE PROFESSIONAL APPLICATIONS OF THE ISOVALERIC ACID FLAVOUR STANDARD?
The Isovaleric Acid Flavour Standard serves multiple professional purposes across the brewing industry:

• – Brewmasters and beer tasters use it to identify and assess isovaleric acid levels in hop-forward beers, ensuring quality control and detecting off-flavours caused by old or degraded hops before products reach consumers.
• – Quality control professionals in the brewing industry rely on it to establish acceptance criteria for different beer styles, monitor hop quality and freshness, and detect storage or handling issues that could introduce cheesy or sweaty off-flavours.
• – Sensory analysts and training coordinators use it for comprehensive flavour evaluation programs, training panels to distinguish between acceptable hop character and undesirable isovaleric acid notes, and ensuring consistent assessment capabilities across different facilities and professional certification requirements.

This standard is recognised and recommended by leading brewing organisations worldwide.

OTHER INFORMATION
Flavour Wheel Number: 0613

Flavour Level: Variable – 0.5 – 2 mg / l

Isovaleric Acid Flavour Standard is the recommended flavour standard / sensory reference standard of: American Society of Brewing Chemists (ASBC) and the European Brewing Chemists (EBC).