The application of flow cytometry in microbiological monitoring during winemaking: two case studies

In this work, we exploit a general flow cytometry technique involved in the differentiation of live and dead yeast cells for two applications in winemaking. The discrimination of yeast populations is achieved using two fluorescent dyes that measure the metabolic activity and membrane integrity of the yeast. This analytical approach is first applied for quality control of active dry yeast. Results are discussed in comparison with the Codex Oenologique International (International Oenological Codex) of the International Organisation of Vine and Wine (OIV), demonstrating that analysis using flow cytometry is a valuable alternative, given the ease of execution and the high quality of results obtained in terms of reproducibility, repeatability, and confidence interval. In the second case, we apply flow cytometry as a technique for monitoring the production of sparkling wines using the “Champenoise” method, and describe the evolution of yeast through the production process. In this case, results are directly compared with those obtained with the two methods (plate counts and direct microscopic count) listed in the OIV standards, in order to ensure a thorough understanding of the improvements related to the use of flow cytometry.