Manometric Determination of I(—) Malic Acid in Grape Musts and Wines

Abstract

The manometric determination of malic acid is specific, rapid and more convenient than other methods of analysis and, by introduction of 0.5 to 1 ml sample, it extends well over the whole range of concentrations of malate found in grape musts and wines. No preliminary treatment, such as the removal of tartrate and sugars, is necessary and the sample is directly introduced into the Warburg flask. The method has been tested for additional carbon dioxide evolution from fermentation concomitant with malate decarboxylation and from decarboxylation of oxalo-acetate, pyruvate and fumarate and no interference from these side reactions with the analysis was detected.

The effect of ethanol on the enzyme system has been investigated. It was found to have no inhibitory influence on the decarboxylation unless the overall concentration exceeded 24 per cent by volume. The accuracy of the method was confirmed by determining malic acid in samples of grape must and wine containing incremental additions of the pure compound.