Carboxylic Acid Composition of Authentic Varietal and Commercial Grape Juices

Abstract

Abstract Quantities were determined of tartaric, malic, citric, lactic, succinic, and shikimic acid present in juices produced by cold and hot pressing from 56 grape cultivars grown in Ontario for the 1988 and 1989 seasons. The individual acids were separated by liquid chromatography (LC) and detected at 210 or 250 nm. Lactic and succinic acids were determined enzymatically. The ranges of acid concentrations found were as follows: tartaric, 4.19-13.51 g/L; malic, 1.68-15.36 g/L; citric, 0.305-1.158 g/L; lactic, 0.015-0.388 g/L; succinic, 0.002-0.075 g/L; and shikimic, 0-0.102 g/L. Tartaric and malic acids were the major acids in every cultivar. The tartaric:malic acid ratio ranged from 0.52 to 4.36, but it was >1.0 in most cases. Genotype had significant effect only on the shikimic acid content. Hot pressing of red cultivars yielded juice with significantly higher pH and tartaric, citric, lactic, and total acid contents than cold pressing. Vintage had no significant effect on acid composition. The total acid content determined by LC was always considerably higher than the titratable acidity, but good correlation existed between the 2 measurements. Most commercial grape juice had similar composition to that of authentic juices. However, tartaric acid content was lower in the majority of commercial juices because of losses during the detartration process. Also, indications of acidulation existed in some of the commercial juices.