Changes in the Concentration of Malates, Tartrates, and total free Acids in Flowers and Berries of Vitis Vinifera

Abstract

In eight grape varieties studied from April 20 to October 20, tartrate, malate, and total titratable acids increased rapidly in the flowering parts of the vine up to early bloom. The levels declined during late bloom and berry set. During prebloom and bloom periods, tartrates were present in amounts two to five times as great as the amounts of malate. After shatter, concentrations of both acids in the berries increased rapidly for about 4 weeks, a period corresponding closely to the period of rapid growth of berries.

Tartrates and malates remained at a high level in about equal amounts until the berries began to change color and ripen. The ripening period (July 22 to Sept. 18) was associated with sharp decreases in malates and tartrates in all varieties. During the ripe and overripe stage of maturity, tartrates remained at about the same level, while malates and total titratable acidity continued to decrease.

The varieties studied were classified into two groups according to the average ratio of tartrate to malate (T/M) at berry maturity. Low-malate varieties (T/M ratio greater than 2.5) included Thompson Seedless, White Riesling, Emerald Riesling, and Semillon. High-malate varieties (T/M ratio less than 1.5) included Sylvaner, French Colombard, Barbera, and Carignane.