Enzymatic Determination of L(-)malic and L(+)lactic Acids in Wine by Flow Injection Analysis

¹ Physical Chemistry Department, Faculty of Pharmacy, University of Porto, R. Anibal Cunha 164, 4000 Porto, Portugal
² College of Biotechnology, Portuguese Catholic University, R. Dr. Antonio Bernardino de Almeida, 4200 Porto, Portugal.

The enzymatic determination of L(-)malic and L(+)lactic acids in several types of wines by flow injection analysis (FIA) with spectrophotometric detection is described. This flow injection system, which incorporates a dialysis unit for adjusting the composition of the injected solutions to the requirements of the measuring system, enables determinations of these two organic acids without the need for any prior treatment of the wine samples, with a concentration interval of between 0.02 and 4 g/L, and a sampling rate of approximately 20 determinations per hour. The results obtained with this FIA method for various types of Portuguese wines are in good agreement with those of the batch method which uses the same enzymatic technique and are quite precise as they present a coefficient of variation below 2.5%.

Key words: flow injection analysis, L(-)malic acid, L(+)lactic acid, spectrophotometric enzymatic determination, wine

Submitted on April 11, 1991