Microbes and long term stability of bottled wine

This workshop, the first in the Saanich Sommeliers Workshop Series on November 23, 2020 provided an opportunity for club winemakers to learn about issues in bottled wine including  those associated with undesired microbial growth during fermentation and post fermentation, as well as well as management of post bottling defects such as protein haze, potassium bitartrate precipitates and colour instability. The worksh was conducted by video conference call.  Selected educational material currently made available to the public by the Enartis corporation formed the basis for discussion. Questions arising from the educational material were directed to an Enartis representative responsible for the British Columbia Washington and Oregon regions.  Responses  were grouped to  original questions for readability.

About Enartis:  Enartis Italy is a growing oenological supply and service company with branch offices in the USA and elsewhere. Enartis has created a substantial number of educational, instructional and promotional webinars for commercial wineries and winemakers in general.

Learn more by reviewing:

Post bottling wine defects  Newsletter  


The greatest interest by participants was in microbial management in fermenting wine and particularly in two Enartis chitosan products derived from Aspergillus Niger, Stab Micro and Stab Micro M.     Stab Micro M may be used during active fermentation to control growth of undesirable microbes while Stab Micro is intended to be used at the end of fermentation.

Q:   Chitosan is promoted as having the capacity through anti-microbial activity to reduce SO2 in winemaking. Can it replace anything else?

Answer to this and related questions: Chitosan makes wine more stable from a microbial perspective.   It thereby reduces the quantity of SO2 required for microbial stability but it is not an anti-oxidant like SO2. That function should be considered separately, but yes SO2 can be pulled back a bit.

Use chitosan as soon as possible in the fermentation process for maximum anti- microbial activity.  There are no negative consequences to its use at listed dose rates.  While the antimicrobial effects of Enartis chitosan products are observable, quantifying results of additions to specific reductions in microbe numbers are difficult as each batch of wine has different fermentation characteristics.

Chitosan can replace the use of lysozyme in the control of gram positive bacteria in the later stages of wine fermentation.  Like lysozyme it can also be used to halt malolactic fermentation

Chitosan help with stuck fermentations by acting on spoilage bacteria that are competing with Saccharomyces cerevisiae yeast.

Chitosan also acts as a fining agent and can replace filtration to a certain degree. It needs to be used separately from other fining agents. Rack wine off lees two to three days after chitosan additions.


Q:  Odors such as volatile acidity and others. How long should one wait before acting on odors in fermenting wine; are bacteria the real problem?

Answer:  If you smell something it may already be too late.   An early indicator can be found  in the fermentation lees.   Smell or taste the lees before an odor in the wine is evident. Quite often the greatest damage to the wine is muting the expression of its real or varietal character.

Protein Haze

Q:   Is bentonite the only mechanism for preventing protein haze in white and rose wine?
Answer. Enartis recommends chipping away at grape proteins during winemaking instead of heavy bentonite fining on a clear wine.   This approach  includes use of products containing protease enzymes at the start of fermentation, the use of condensed skin tannins to precipitate the proteins and additions of mannoproteins to stabilize the wine proteins. The first two measures can significantly reduce the volumes of bentonite to be added.

More information:  Before adding bentonite on a  wine post fermentation it may be beneficial to conduct a heat stability test.  This can be followed by complete bentonite fining trials if necessary.   Good information on both methods  is available on the Australia Wine Research website.

Heat stability test

Bentonite trials

Potassium tartrate stabilization 

Q:  Does the use of KPA increase levels of potassium in wine as that could be a health issue?
Answer:  Yes it does, but when comparing potassium levels in treated vs untreated wine the differences are negligible.

Color Stability

Q;   Does yeast have an influence on colour in red wine?
Answer:  Color instability hasn’t been a widespread problem associated with yeasts.   Color in red wines stabilizes in barrels.  Additions of Gum Arabic may also be useful.

   Tannin VR Supra sold by Scott Labs. What is the Enartis product?  Pro Tinto a combination of tannin and mannoproteins

   Color stability with last minute blending?  It is very common  problem;  try bench trial first.

Contributed by Ken Stepushyn

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