The Effects of Sun Exposure on the Compositional Development of Cabernet Sauvignon Berries

Abstract

The effects of sunlight on Cabernet Sauvignon fruit clusters were studied in a Napa Valley, California, commercial vineyard. Clusters were chosen from sun-exposed locations and from locations shaded by the grapevine canopy. Selected exposed and shaded clusters on one vine were monitored for air temperature and light flux. Berry samples were collected weekly from anthesis and were analyzed for tartrate, malate, glucose, and fructose by HPLC and for potassium by emission spectroscopy. Berry juice was also analyzed for pH, titratable acidity, and soluble solids content. Data were presented both on a concentration basis (mg/g fresh weight) and on a per berry basis (mg/berry). Sun berries were significantly higher in concentrations of tartrate, malate, glucose, and fructose as shown by analysis of variance. No significant differences were found when expressed on a per berry basis, however. Potassium expressed either as concentration or per berry, pH, titratable acidity, and soluble solids showed no significant differences between sun and shade berries. Berries from the canopy shade were significantly heavier than berries exposed to the sun. The observed differences in concentration were attributed to a higher water content in the berries from shaded clusters.