Pre-fermentation microbiota

The second point of entry of microorganisms into the winemaking process is from the winery flora. Several studies have examined the impact of winery microbiota in wine production, and as would be predicted, this impact depends upon sanitation and inoculation practices and when the study was conducted during the production season as microbial populations build up on winery surfaces as fruit continues to be received. Thus the local winery population impacting the first fruit to arrive at the winery is fewer in number than the local winery population impacting fruit harvested and processed much later in the same season. The nature of the community also differs. As the season progresses, the winery microbiota becomes dominated by Saccharomyces (Bisson Joseph, 2009 Renouf, Perello, Strehaiano, Lonvaud-Funel, 2006). 

In addition to common soil and plant bacteria that do not persist in wine formation, members of the lactic and acetic acid bacterial families can be found on the surface of the grape. These bacteria can pose a problem in wine fermentation, particularly if an antimicrobial agent like sulfur dioxide is not used or if the yeasts are inhibited in their ability to dominate the fermentation, allowing other organisms to proliferate. The metabolic activities of these bacteria often lead to high acetic and organic acid concentrations that can be inhibitory to yeast. 

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