Restarting Stuck Malolactic Fermentations

Last updated: 5/2022

Applies to: Winemakers dealing with stuck malolactic fermentations. Contains a pdf download of the protocol and accompanying worksheet.

Prior to restarting a malolactic fermentation, read our Troubleshooting Guide for Sluggish MLFs. There are many factors that can influence the success of a malolactic fermentation (MLF). Before jumping into a full restart, it is a good idea to assess each of these factors. Sometimes only a small adjustment is needed to help an MLF complete successfully.


Prepare the Stuck Wine

step 1 Add 30 g/hL (2.5 lb/1000 gal) of RESKUE™ prior to restarting. Suspend RESKUE in 10 times its weight of warm water at 30–37°C (86–98°F) (see pg 55 for more about RESKUE). Wait 20 minutes then add to stuck wine.

step 2 Allow RESKUE to settle for 48 hours then rack off the settled lees.

step 3 Adjust temperature of RESKUE-treated wine to 18–22°C (64–72°F).

Malolactic Nutrient Addition:

step 4 Add 20 g/hL (1.7 lb/1000 gal) of ML RED BOOST™ to RESKUE-treated wine. When restarting a stuck MLF, ML RED BOOST is used for white, red, and rosé wines.

step 5 Mix gently and wait 24 hours before bacteria addition.

Malolactic Bacteria Addition

step 6 Add a double dose of LALVIN VP41™ and mix to homogenize. To determine how many packets of bacteria to add: double the volume of stuck wine. Then, add enough bacteria packets to treat that volume*.

step 7 Check for MLF activity by analyzing L-malic acid degradation every 2–4 days.

*VP41 is sold in packets that treat 66 gal, 660 gal, or 6600 gal. Use any combination of packets that best approximates the volume
calculated in step 6

pdf Download

For a printable pdf download of the protocol above and accompanying worksheet, please click below.


Learn More

To avoid stuck and sluggish malolactic fermentations, consider using the Malolactic Fermentation Feasibility Evaluation. The scorecard rates how antagonistic several wine conditions are to ML bacteria and returns a total point value representing the predicted difficulty of MLF. Based on this value, Scott Laboratories recommends certain steps be taken to maximize success.