Microbiological Analyses at Vinlab – What to ask for?

Brettanomyces Unfold
July 27, 2018

Caitlyn McCartney – August 2018

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What is the status of my tank/barrel?

Microscopic identifications (MicroID) are useful when checking the status of wine in tanks/barrels. Both yeast and bacteria can be identified under the microscope when populations present are over 1000-2000 cells/mL, however, a microscopic identification will not tell you whether the yeast or bacteria is viable or not, or exactly how much yeast and bacteria is present.

Micro ID’s go hand in hand with chemical analyses and can be used to make sense of various results; such as high VA’s could be due to Lactobacillus or Acetobacter populations present. Active fermentations due to residual substrates may be a result of yeast or bacteria populations present.

What is this haze or sediment in my wine?

Various hazes and sediments can easily be identified under the microscope, whether the source be microbiological, crystalline, proteins, polyphenols, wine processing aids and/or non-wine typical sediments (cork pieces).

Am I ready to inoculate?

Cell count and viability testing is appropriate when inoculating juices before fermentation and when inoculating base wines for secondary fermentation in sparkling wine production. Cell count and viability testing requires samples having 1000-2000 cells/ml.  A cell count of > 106 cells/ml and viability of > 50% should start a fermentation successfully. Cell count and viability testing should be used as an estimation only, and is not appropriate when it comes to bottled wines which require a sensitivity of 1 cell/mL.

Are there any viable microbes in my wine?

Culturing/plating is a sensitive means of not only identification of yeast and bacteria in wines, but also informs you whether the microbe population present is viable or not. Culturing is a more sensitive method than a microscopic ID and yeast cell count, and can be selective for specific yeast or bacteria; e.g. Brettanomyces.

Bottled Wines

A sterility test is a rapid method to test for the growth of any microbes in wines post-bottling. Growth on plates may indicate bottling line contamination and potential bottling line sterilization and sanitation problems. Therefore, the sterility test only proves adequate for wines that have been sterile filtered, as wines that have not been sterile filtered could have growth of microbes present in the wine and not from bottling line contamination.

Export Requirements – How do they help me?

Due to the low pH, high-alcohol environment of wine human pathogens cannot survive, however, many countries require specific microbiological analyses using selective methods for export/import purposes. These include; total coliforms, E. Coli, Staphylococcus, total plate count and yeast and mould.

What about beer analysis?

Filter/direct plating on three types of media is required for beer analysis. Yeast culture, aerobic bacteria and anaerobic bacteria plating is performed. Further identification of colonies grown is performed via microscopic identification as well as gram staining. These tests are all simply performed by selecting “Micro analysis” on the Beer Analysis Request Form.

Panels – When to ask for what panel and how do I know I need a panel?

Various panels are available which incorporate both chemical and microbiological analyses for your convenience.

When 4-EP and 4-EG is sensorially detected, or when filtration decisions are being made, the Brettanomyces management panel may be useful. This panel includes selective plating for Brettanomyces and the chemical analyses of 4-EP and 4-EG.

To monitor fermentation efficacy, or when wondering whether you have a stuck/sluggish fermentation the stuck/sluggish fermentation panel provides comprehensive chemical and microbiological analyses. Microbiological analyses include a Micro ID, yeast cell count and yeast viability, which ties up to the chemical analyses of glucose/fructose, VA and MLF.

If your malolactic fermentation appears to be lagging the stuck MLF panel could help, combining the chemical analyses of alcohol, pH, SO2, and malic acid levels (all directly affecting MLF) and the microbiological analyses of bacteria plating (indicating viable bacteria populations) and a Micro ID.

Wondering whether to sterile filter? The filtration panel combines chemical analyses focused on residual substrates (glucose, fructose and malic acid) frequently responsible for refermentations in the bottle, turbidity, VA, and pH. This is incorporated with the microbiological analyses of a Micro ID and a Brettanomyces and bacteria culture ensuring no spoilage microbes are present.

For your convenience, a table listing turnaround times and volumes required follows.

Analysis Maximum turnaround time Volume Required Detection limit
Microscopic Identification 24 hours 5 mL 1000-2000 cells/mL
Yeast cell count and Viability 24 hours 5 mL 1000-2000 cells/mL
Direct Plating 7 – 10 days 1 mL 1 cell/mL
Sterility 3 days 100 mL* 1 cell/100 mL
Export Analysis 5 days 100 mL/Export analysis* 1 cell/100 mL
Beer 7 days 100 mL** 1 cell/25 mL

*These tests are performed on bottled wines only and, therefore, volumes listed are minimal amounts, and full, bottled, unopened wines are required.

**If possible, please send in an extra bottle for beer analysis. This allows us to perform the filter plating method giving a more accurate sample representation.