(NewWorldWinemaker) - Phenolic compounds affect several sensory components of wine, including red wine color, astringency, bitterness, and olfactory profile. Though present at low levels, their concentrations are a primary factor in the differences between wine types and styles. They are also important oxygen reservoirs and substrates for browning reactions.Their concentrations are largely due to processing considerations (for example, flavonoid content increases with increased skin contact time and temperature).