ELECTROCHEMICAL BIOSENSORS FOR ASSAYS OF L-MALIC AND D-LACTIC ACIDS IN WINES

The knowledge of L-malic acid concentration is important for the follo w-up of grape maturation and of malolactic fermentation; in the same w ay, D-lactic acid concentration gives information about the growth of lactic piqure. A simple and inexpensive assay method is proposed with the use of amperometric biosensors developed for this specific applica tion. The results are compared to those obtained with the enzymatic sp ectrophotometric method (Boehringer kit). The difference between the t wo measurement results shows that colored substances interfere with th e compounds assayed in the case of red wine. To minimize this effect, two methods are proposed: a differential measurement or the addition o f 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.