The growth of non-starter (or indigenous) microorganisms in musts can significantly impact the efficacy of inoculated Saccharomyces growth and function. Alternatively, growth of non-Saccharomyces yeast populations may provide complexity to wine flavor and aroma. New methods have recently been developed to directly characterize the microorganisms in a particular habitat without the need of enrichment or isolation. Typically these strategies examine the total microbial DNA (or RNA) derived from mixed microbial populations to identify individual constituents. In this report the Authors wanted to demonstrate that the molecular method (using PCR-DGGE) they have developed is a potential alternative to traditional plating scheme for simple monitoring of yeast populations in commercial wine fermentations. The wine fermentations were a blend of Semillon and Sauvignon blanc grape varieties processed in Oakville (California). The fermentations were carried out in four oak barrels by indigenous yeasts. Yeast strains including Metschnikowia, Candida and Pichia species persisted during the early stages of the fermentation. Eight days into the fermentation the emergence of S. cerevisiae. Interestingly two Candida species were present throughout the complete fermentation long after the emergence of S. cerevisiae. This fact may impact the sensory and stability characteristics of the final wine.

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