unwanted malolactic fermentation by lactic acid bacteria in specific wines

undesired malolactif fermentation

How to prevent undesired malolactic fermentation

Winemakers of most white wines in Alsace, some in California, some in Champagne, and sparkling wines need to prevent malolactic fermentation. According to different oenological scientific papers, critical threshold level of lactic acid bacteria growth trigerring malolactic fermentation would start around 10 exp 6/mL….

Lactic acid bacteria population during malolactic fermentation
lactic acid bacteria growth at beginning & end of malolactic fermentation (see arrows)

Prevention better than cure...

It is out of question for the winemaker to wait lactic acid bacteria (Lab) to reach such critical levels in their wines. Therefore it is vital to monitor the growth of lactic acid bacteria during winemaking .

However Lab growth surveillance is hindered by 7 to 10 days incubation time for plate count results.

In between lactic acid bacteria will continue growth, reaching critical thresholds once reached triggering irreversible enzymatic conversion of malic acid and modifying the organoleptic properties of the produced wine.

Besides being costly for winemakers, PCR methods are responsible of false positives not able to discriminate dead oenococcus oeni DNA (many dead bacteria keep their membrane with their intracellular DNA, filtration not eliminating them) from real viable oenococcus oeni DNA.

Besides other bacteria as pediococcus may grow and trigger undesired malolactic fermentation. Physical separation of lactic acid bacteria from yeast is not possible.

4 hours instead of 10 days...

A rapid on-site alert tool Wine Alert based on selective ATP bioluminescence detection developped originally for Brettanomyces detection, may be used with different patented reagents so as to destroy completely yeasts and remove its ATP, so as to analyze lactic acid bacteria ATP.

Test performed at Aquitaine Microbiologie lab in Bordeaux, validated the rapid yeast kill time of these reagents, not affecting lactic acid bacteria tested.

Brett cell before & after treatment

Yeasts lysed after formulation contact

You see above microscopy pictures taken by Aquitaine Microbiologie validating yeast cell membrane lysis within 6 hours contact time , but other results validated 4 hours contact time preserving lactic acid bacteria viability (as shown below within 4 hours and 18 hours contact time). Various yeast killing reagents were validated on different wine yeasts ..

Brettanomyces cell lysis not damaging lab
Assay principle of lactic acid bacteria within 4 hours:
  1. Mixture of wine sample with yeast kill formulation for 4 hours.
  2. Sample concentration inside a cuvette-filter bottom combination.
  3. Flushing wine inhibiting substances and free ATP from grapes or dead microorganisms.
  4. Viable lactic acid bacteria cell lysi and release of its intracellular ATP.
  5. Luciferin-luciferase is added to analytical cuvette.
  6. ATP Bioluminescence of released lactic acid bacteria ATP is measured in our specific bioluminometer.
cuvette flter flushing & cuvette filter in bioluminometer

Higher the bioluminescence signal, higher the viable lactic acid bacteria cells within the wine sample. To the opposite of PCR test kits not discriminating dead from live bacteria, this selective Atp bioluminescence assay will only detect viable lactic acid bacteria, including viable but non culturable, but will not trigger false positives with dead oenococcus oeni cells.

Are you winemaker, winemaker consultant, looking for a rapid alert tool to screen pre-critical threshold of lactic acid bacteria before malolactic fermentation triggers, so as to take immediate corrective action? Use our Contact form for more informations.