Physiological and Biochemical Events During Development and Maturation of Grape Berries

Some of the most important physiological and biochemical processes that occur during the development and maturation of de Chaunac grape berries have been investigated. The studies included monitoring changes in the pH, in total and individual major acids, cations, sugars, anthocyanins and their biosynthetic enzymes. Brix, pH, K⁺, sugars and anthocyanins showed a sharp rise during and immediately after véraison. There was a concomitant rise in the activity of anthocyanin biosynthetic enzymes. Total acidity and malic acid content increased during the first four weeks and declined thereafter, reaching a steady level approximately five weeks later. The concentration of phosphoric acid showed a rise during the maturation process, while tartaric acid levels declined continuously. On the per gram basis, the levels of Na⁺ showed no consistent changes, while Ca⁺⁺, Cu⁺⁺, Mg⁺⁺, and Mn⁺⁺ showed sharp declines during the expansion period of the berries and steady, low levels during the maturation process. The data suggest that the majority of metabolic events in the berries come to a steady state approximately eight weeks after véraison under the climatic conditions of the northeastern United States.