ARS | Publication request: Environmental Influences on Ripening and Phenolics in Grapes

Submitted to: Plant Growth Regulator Society of America Meeting
Publication Type: Abstract Only
Publication Acceptance Date: April 12, 2010
Publication Date: August 10, 2010
Citation: Tarara, J.M., Absjornsen, H. 2010. Environmental influences on ripening and phenolics in grapes. Plant Growth Regulator Society of America Meeting Program Book.

Technical Abstract: During the past decade we refined our understanding of the effects of solar radiation and temperature on grape ripening, especially in red-skinned cultivars used for wine. In three separate studies, we deployed up to ten combinations of berry temperature and exposure to solar radiation, then assessed by HPLC methods the outcome on the classes of phenolic compounds that are most of interest to the grape and wine industry: flavonol-glycosides, anthocyanins, and proanthocyanidins in the berry. When the diurnal fluctuation in berry temperature was reduced, or damped, by cooling the berries during the day and heating them at night, the onset of ripening was accelerated. Concentrations of flavonol-glycosides increased with exposure to solar radiation, but these compounds were insensitive to field temperatures. High berry temperatures and a combination of low light and high berry temperature decreased the total concentration of anthocyanins at harvest. At equal temperatures, shaded and sunlit berries differed in the proportions of acylated derivatives and dihydroxylated anthocyanins. Higher berry temperature was positively associated with higher concentrations of skin proanthocyanidins at the onset of ripening, when concentrations are at their maximum. The consequences for wine quality from many of these compositional changes are not yet understood.