Analysis Request – Wine
Microbiological processes essentially govern the fermentation process in which yeasts and bacteria consume grape sugars, amino acids, organic acids and various other compounds with the intent of forming a microbiologically stable final product. These yeasts and bacteria are introduced into the winemaking process by either arriving on fruit, or are already present in the winery, having the ability to not only survive, but if conditions permit, proliferate during the winemaking process. Although essential to the process, not all yeasts and bacteria are beneficial making it necessary to monitor various microbiological aspects throughout the winemaking process.
Various Microbiological checks can be implemented throughout the entire winemaking process, with Yeast Cell Counts and Yeast Cell Viabilities being an effective tool in determining whether juice will undergo a successful fermentation. Microscopic identifications are useful when checking the status of wine in tanks or barrels in which both yeast and bacteria can be identified. When requiring a more sensitive method various culturing methods on selective media can be used to identify different strains of yeast and bacteria. When wanting to determine the effectiveness of sterile filtration, sterilities are useful where any growth in culture may indicate bottling line contamination.
Microscopic identification goes hand in hand with chemical analyses and can be used to make sense of various results, such as high volatile acidities could be due to Lactobacillus or Acetobacter populations present. Active fermentations due to residual substrates (residual sugar and malic acid) may be a result of viable yeast or bacteria populations present making detection and enumeration of these populations beneficial. Many wine faults are also often associated with yeast and bacteria populations, with 4-ethyl phenol and 4-ethyl guaiacol reaching sensory thresholds due to the yeast species Brettanomyces, while Lactobacillus populations may result in wines having elevated levels of Acrolein, a mousy character or even a ‘Geranium’ taint. Knowing and understanding the microbes present in your wine gives you as the winemaker the insight to intervene where and when necessary.
How often and when?
Testing requirements depend on where you are in the winemaking process. Microbiological tests used to monitor the progress of fermentations should naturally occur throughout the fermentation process. During fermentations if volatile acidities are rising and malolactic fermentations in tanks and barrels are struggling to complete more frequent testing would be required. Sterility checks should be performed post-bottling. A range of other tests can be performed should problems arise, including sediment identification, selective plating for Brettanomyces and Bacteria, and the molecular methods of Scorpion panels in which various wine yeast and bacteria strains are identified.
In these critical stages of production, everyone involved should understand the importance and impact of the necessary microbiological analyses in the winemaking process.