Accumulation of tartaric acid in the ripening process of grapes

Abstract

1. Tartaric acid content in grapes gradually increased with ripening and reached a plateau about 50 days after flowering. 2. Tartaric acid synthesis from 14C02 was predominant in an early ripening stage. When the berries were exposed to 14CO2 8 days after flowering and examined two days later, 30% of the total 14C fixed was found in tartaric acid. Subsequently, a part of the tartaric acid decomposed, but the greater part remained in the berries in a salt form. At the last stage of the ripening process (82-100 days after flowering), some of the tartarate was again converted to free acid. No 14CO2 was incorporated into tartaric acid when berries were exposed 61 days after flowering. 3. L(+)-Tartaric acid-l,4-14C fed to the berries was catabolized to 14CO2. The ratio of radio activity recovered as 14 CO2 to that fed was nearly constant throughout the ripening process. The cause of tartaric acid accumulation in grape berries is not thought to be due to a lack of catabolizable enzymes, but to formation of an insoluble salt which is scarcely effected by such enzymes.