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Cider apples contain high amounts of phenolic compounds, which are nutritionally significant substances. Using cider apples could prove a pertinent way forward for developing innovative high-nutritional-value apple juices, but not if it compromises organoleptic quality, such as excessive astringency due to the tanning properties of certain polyphenols complexing with specific salivary proteins like proline-rich proteins (PRPs).

When apples are processed into juice, the enzymatic oxidation of polyphenols generates new polyphenolics ("oxidation products") with original structures, but little is known about their nutritional and organoleptic properties.

To address this gap, we set out to characterize the structures and study the tanning properties of products resulting from the oxidative dimerization of chlorogenic acid, the main phenolic acid in apple juice.

Precipitation of various salivary proteins by a mixture containing several chlorogenic acid oxidation products was measured, and we found that these oxidized phenolics significantly interacted with statherin/P-B peptide and cystatins whereas precipitation was significantly weaker for the PRPs.