polyphenols

Polyphenols are a broad class of compounds bearing multiple phenol groups. In a 2016 study analyzing 34 commercial lager brands, the composition of phenolic acids and polyphenols displayed diverse profiles by brand.

In sensory evaluation from the same study (10 of the 34 brands assessed), beers high in both polyphenols and hop acids were perceived as harsh and progressively increasing in bitterness. However, this experimental design did not separate individual polyphenols for evaluation, and a uniform bitterness intensity cannot be assigned to the polyphenol class as a whole.

Polyphenols are a heterogeneous class and are treated as a group of compounds that may contribute not only to bitterness but also to mouthfeel. The 2016 study discussed the character of beer bitterness in the presence of hop acids, not an isolated contribution from polyphenols alone.

In another study, when 81 hop-derived phenolic compounds were subjected to structural annotation, intensely dry-hopped beers were reported to reach a maximum of 159 mg/L, matching or exceeding the humulinone and iso-alpha-acid concentrations in the same beer. Though equal concentrations do not necessarily entail equal sensory contribution, the authors themselves state that the sensory role of hop phenols remains poorly understood, leaving the relationship with hop bitter acids unresolved.