isovaleric acid

Technical specification

Assessment

The best way for assessors to evaluate isovaleric flavour in beer is as follows. Cover the beer with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary.

Amount of flavour per capsule

3.0 mg er capsule

Threshold

The flavour threshold of isovaleric acid is 1 mg / l.

Origins

Isovaleric acid is derived from breakdown of alpha-acids in hops. It is imparted to beer by use of high hopping rates or degraded hops or hop extracts. Isovaleric acid can occasionally be produced by wild yeasts, specifically Brettanomyces spp which may be present either as contaminants or introduced into beer for conditioning purposes.

Confusions

Professional beer tasters can confuse isovaleric acid with the following flavours:

• Butyric acid
• Ethyl butyrate
• 2,3-Butanedione

Importance

Isovaleric, sweaty, cheesy flavour notes are characteristic flavours of some beer styles, eg India Pale Ale. Typical ‘cheesy’ characters are often associated with beers of very high bitterness. In pale lager beers, isovaleric character is regarded as an off-flavour.

CAS registry number

The CAS registry number of isovaleric acid is 503-74-2.

Other names

• 3-methylbutanoic acid
• isobutyl formic acid
• delphinic acid
• dephinic acid
• 3-methyl butanoic acid
• 3-methyl butyric acid
• beta-methyl butyric acid
• 3-methylbutanoic acid
• isopentanoic acid
• isopropyl acetic acid
• isovalerianic acid

Remarks

The intensity of isovaleric flavour increases with decreasing beer pH value.

Threshold distribution

Capsules per pot

10

Legal notices

This product is protected by the following trade marks and patents:

• US Patent no. D679900
• European Community Trade Mark
  Registration no. 009937574
• European Community Trade Mark
  Registration no. 009856527
• US Trade Mark Registration no. 4345057
• US Trade Mark Registration no. 4345056