Modelling Biolog profiles' evolution for yeast growth monitoring in alcoholic fermentation.

AIMS: A research was undertaken to explore the possibility to express with suitable mathematical models Biolog metabolic curves obtained for oenological yeasts and to use such models for monitoring yeast growth in alcoholic fermentation. METHODS AND RESULTS: Experimental curves of metabolic activity in Biolog YT microplates, obtained in a previous work for various oenological yeast strains in pure cultures and mixed populations, at various cell concentrations, have been modelled with Gompertz's, Gompertz's modified and Lindstrom's mathematical equations. Lindstrom's model proved to be the most suitable to fit the curves of the oenological yeasts under study, providing the highest correlation coefficients between experimental and calculated data. The model made it possible to recognize, in mixed yeast populations, the presence of active dry yeasts used for guided fermentations. Model's constant parameters were used for a numerical characterization of yeast curves. CONCLUSIONS: The application of the model to the experimental data resulted to be suitable for an early prediction of the successive evolution of yeast growth. SIGNIFICANCE AND IMPACT OF THE STUDY: The results obtained indicate the possibility to develop protocols for monitoring yeast presence during alcoholic fermentation, with an early assessment of the correct evolution of their growth, especially when active dry yeasts are employed.

Possible use of Biolog methodology for monitoring yeast presence in alcoholic fermentation for wine-making.

AIMS: A research was undertaken to explore the possibility to use Biolog system of microbial metabolic characterization for the monitoring of yeast population evolution during alcoholic fermentation for wine production. METHODS AND RESULTS: An application of Biolog system was employed for the characterization of yeasts of oenological interest, in pure cultures and mixed consortia, in various cell concentrations. The system's capacity to discriminate among different cell concentrations of the same yeast strain was ascertained, along with the capacity to discriminate between mixed and pure populations. CONCLUSIONS: The tested application of Biolog system resulted suitable for a quick recognition (24 h) of the presence of starter cultures within mixed populations of autochthonous yeasts. Such discrimination was confirmed with the one resulting from molecular techniques. SIGNIFICANCE AND IMPACT OF THE STUDY: The study suggests the possibility to employ Biolog system for an early monitoring of yeast evolution in modern wine-making fermentations, where specialized yeasts are more and more frequently used as starters and their ability to overcome autochthonous yeast populations is crucial.