Rapid detection of viable yeasts and bacteria in wine by flow cytometry

The potential of using flow cytometry (FCM) in combination with fluorescent dq;es for rapidly estimating counts of yeasts and malolactic bacteria in l aboratory media and wines was examined. In general, there was a good correl ation (regression coefficient, 0.94) between viable counts of yeasts determ ined by FCM and by standard plate assay. The FCM detection limit of yeasts in YPDE medium and in Pinot noir must was 10(3) cells/ml. The lowest bacter ial concentration detected by FCM was 10(4) cells/ml. When yeast and malola ctic bacteria populations were simultaneously analysed in wine by FCM witho ut any previous sample treatment, difficulties were encountered in the coun t of bacterial cells due to their size, which is similar to natural debries present in wine. However, after the optimisation of the sample preparation , the technique appeared promising in determining the presence of such micr oorganisms in wine with one single measurement. Because it is rapid and eas y to use, flow cytometry can be considered a useful method for microbiologi cal quality control in wineries and for the investigation of the growth dyn amics of microorganisms in wine. (C) 2001 Elsevier Science B.V. All rights reserved.