Electrochemical Biosensors for Assays of L-Malic and D-Lactic Acids in Wines

¹ Laboratoire de Génie Chimique et Électrochimie (URA CNRS 192), Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France.

The knowledge of L-malic acid concentration is important for the follow-up of grape maturation and of malolactic fermentation; in the same way, D-lactic acid concentration gives information about the growth of lactic piqûre. A simple and inexpensive assay method is proposed with the use of amperometric biosensors developed for this specific application. The results are compared to those obtained with the enzymatic spectrophotometric method (Boehringer kit). The difference between the two measurement results shows that colored substances interfere with the compounds assayed in the case of red wine. To minimize this effect, two methods are proposed: a differential measurement or the addition of charcoal to the sample for the adsorption of colored substances. The short response time allows analysis of 100 samples every day, and the biosensor can work for one month with the same enzymatic solution.

Key words: amperometric biosensors, L-malic acid assay, D-lactic acid assay, malolactic fermentation, wine

Submitted on February 23, 1995