Representing the most common flavonoid consumed in the American diet, the flavan-3-ols and their polymeric condensation products, the proanthocyanidins, are regarded as functional ingredients in various beverages, whole and processed foods, herbal remedies and supplements. Their presence in food affects food quality parameters such as astringency, bitterness, sourness, sweetness, salivary viscosity, aroma, and color formation. The ability of flavan-3-ols to aid food functionality has also been established in terms of microbial stability, foamability, oxidative stability, and heat stability. While some foods only contain monomeric flavan-3-ols [(-)-epicatechin predominates] and dimeric proanthocyanidins, most foods contain oligomers of degree of polymerization values ranging from 1-10 or greater than 10. Flavan-3-ols have been reported to exhibit several health beneficial effects by acting as antioxidant, anticarcinogen, cardiopreventive, antimicrobial, anti-viral, and neuro-protective agents. This review summarizes the distribution and health effects of these compounds.

Generally referred to as polyphenols (PPs), beer flavonoids such as the flavan-3-ols and their condensed products, the proanthocyanidins, represent a class of readily oxidizable compounds capable of hindering or preventing the oxidation of other molecules present in beer. Flavan-3-ol and proanthocyanidin capacity to improve oxidative stability has been well established in other food systems, and thus these antioxidants have recently gained significant consideration as potential beer flavour modifiers and/or stabilizers. The duality of their presence in beer is that PPs complex with proteins in the beer matrix to form temporary and permanent hazes. Undesirable physical instability caused by PP-protein interactions can be resolved via use of adsorptive resins such as polyvinylpyrrolidine. While there is no doubt that polyphenol removal increases beer shelf stability in terms of haze formation, the impact of polyphenol removal on beer flavour remains unresolved. This review discusses the sources, content and impact of polyphenol presence and removal on beer physical and flavour stability.

Phenolic polymer material extracted during commercial red wine fermentations (Vitis vinifera L. cv. Pinot noir) was isolated and analyzed to characterize its chemical composition. Phenolic polymer isolates were prepared from samples taken throughout fermentation and isolated by adsorption chromatography. Isolates were subjected to phloroglucinolysis to analyze the proanthocyanidin amount as well as the subunit composition. Results of phloroglucinolysis revealed that the proanthocyanidin content of individual phenolic polymer isolates varied from 27 to 54%. Subsequent analyses were done in an attempt to quantify materials other than known proanthocyanidin subunits. Results of all experiments indicate that up to 82% of the phenolic polymer isolates could be accounted for by mass. While this figure accounts for a significant portion of the polymeric phenolic material, further investigation will be needed to qualify the remaining 18%.

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