N. Darie, et all. Journal of Agroalimentary Processes and Technologies, Volume XIII, No.2 (2007), 359-362 Full Paper – Food Control SELECTIVE BIOSENSORIAL ASSAY IN LACTIC SOURING WINES DISEASE PREVENTION Neli Darie 1 , Claudia Felicia Ognean 1 , M. Ognean 1 , Adriana Gafita 2 , O.S. Petrenciu 1 1 University “Lucian Blaga”of Sibiu, Faculty of Agricultural Sciences, Food Industry and Environmental Protection, Biochemistry Dept., 7-9 Dr.I.Ratiu Street, 550012 Sibiu, Romania, 1 E-mail: neli.darie@ulbsibiu.ro 2 Military Hospital, 46, Victoriei Avenue, Sibiu, Romania Abstract D-lactic acid resulted in case of an accidental stopping of the alcoholic fermentation process, by all sugars converting, changes the wines taste and the wines become sweet and sour. Adding yeasts it can prevent the white and red wines disease lactic souring. The technological parameter D-lactic acid was comparatively measured spectrophotometrically and successfully performed by a selective D- lactic acid biosensor, suitable for oenological applications. There were obtained significant performant functional features of the conceived biosensor (185 sec. as response time, 0.001 mM as detection threshold, 37 days as life time and a good sensibility) in order to detect and prevent earlier the beginning of the wine disease. Keywords: lactic souring, biosensorial assay, D-lactic parameter Introduction During the wine-making process, especially in the alcoholic fermentation, the bacteria can convert the undegradated sugars by the yeasts, in D-lactic acid. The acid hardly influence the wines taste, remaining as such and stamping a sweet and sour taste in the same time (Garcia, 1993). In current practice there is only measured the wine volatile acidity and the oenologists can only suspect the disease appearance when the volatile acidity is higher (Luong, 2003). The premise is false as the parallel formatted acetic acid is responsible for volatile acidity. In order to detect and to early prevent the beginning of the wine disease, the present work concerns to analyse, by an easy assay, a new technological parameter that can be monitories, the D-lactic acid 359