Feature of the Month
Restarting Stuck Fermentations |
Enartis Vinquiry has observed numerous stuck or sluggish fermentations this year, and with our vast experience in this area, we are here to help get your fermentations back on track. First, it is necessary to know some of the wine parameters before restarting a stuck fermentation, otherwise a restart can be difficult or might lead to spoilage. Consider the following questions:
• What is the status of your malolactic fermentation?
• What is the alcohol level?
• How much sugar is there left to ferment?
• Is your yeast viable?
Sending your samples to Enartis Vinquiry for alcohol and glucose/fructose will inform you of the alcohol level and remaining sugar. A microscan and VA will tell you if bacterial activity is a factor. The microscan will also assess the viable yeast concentration, since a successful fermentation is about making conditions better for the yeast. A malic acid test is needed to determine the status of the malolactic fermentation. Depending upon whether there is (L-) malic acid present, shapes the course of action a winemaker would take for a stuck fermentation. If malic acid is depleted, SO2 additions and/or the application of lysozyme should be considered. All analyses mentioned are available in Enartis Vinquiry's Fermentation Assessment Panel - Panel 9.
Extra steps might be required if you find that your wine exhibits analytical properties or conditions that are less than desirable. Once your stuck wine is deemed ready to start, the following steps are Enartis Vinquiry's recommendation on how to restart problem fermentations. If you have additional questions, please call one of our Staff Winemakers for a brief consultation. In more difficult situations, one of our consultants can help map your plan step by step.
METHOD TO RESTART A STUCK FERMENTATION
PRE-TREATMENT OF WINE
In order to prevent the growth and activity of lactic acid bacteria, Enartis Vinquiry recommends the addition of lysozyme in the form of Enartis Zym Lyso and/or SO2 in the form of Effergran, Efferbarrique or Winy. 1-2 lb/1000 gallons of yeast hulls and/or Celferm should also be added to adsorb autolytic toxins. After 24 hours, rack off the lees into a new tank or container.
SELECT ACTIVE DRY WINE YEAST
Select a strain that is both alcohol tolerant and a vigorous fermenter, such as Enartis Ferm EZ Ferm 44 or Enartis Ferm Top 15. Calculate the amount of yeast required for the total volume of stuck wine @ 2-4 lb/1000 gallons. Rehydrate this amount of yeast in ten times its weight in clean water (approx. 1 lb yeast /1 gallon water) at 104°F, allow 15 minutes to rehydrate.
ACTIVATE THE REHYDRATED YEAST WITH NUTRIENTS AND SUGAR
The nutrient content of the stuck fermentation will be low and unable to support adequate yeast growth. Further, yeast are unable to take up nutrients when the alcohol is above about 10%. Nutrients should never be added directly to the stuck fermentation as they can leave residues that would support spoilage organisms and contribute to the possibility of ethyl carbamate production.
Prepare the following initial mixture:
• 2.5 % of volume of stuck wine (25 gal/1000 gal)
• 2.5 % of volume as water (25 gal/1000 gal)
• 1 lb Nutriferm Energy/1000 gallons of stuck wine (approx. 500 g/1,000 gallons)
Adjust sugar level of this mixture to 5°Brix with juice, concentrate or sugar (40 lb sugar/100 gal wine/water mix).
START THE FERMENTATION AND ADD THE STUCK WINE IN BATCHES
Add the rehydrated yeast to this wine/water mix and maintain the temperature at 70°-75°F.
Monitor the sugar level of the starter. When the sugar level has dropped by half (<2.5°Brix), begin to add the stuck wine to the starter. Add in batches of 20% of the total stuck wine volume (total of five additions to the starter). Upon the first 20% addition of stuck wine to the starter, add Nutriferm Advance at a rate of 2 lbs/1000 gallons (of starter + first 20%). When the sugar has decreased by half, add the next batch.
For more information on restarting stuck fermentations, please call (707) 838-6312.
Oct 2010 - Herbaceous Grapes and Juice Analyses
July 2010 - Max Nature and Vintessential Enzymatic Kits
May 2010 - Monitoring Brett and Fenol Free
March 2010 - Microbiology Services and Wine Defects Kits
February 2010 - Wine Improvement Review and Claril SP
January 2010 - Mini Consult and Citrogum
November 2008 - Post Fermentation Analysis
July 2008 - Harvest Analysis
June 2008 - CUNO Filters
May 2008 - Bottling Analysis
March 2008 - Ascent Cork Aroma Evaluation
February 2008 - Wine Improvement Panel
January 2008 - PCR for Spoilage Yeast and Bacteria
August 2007 - Juice Panels
June 2007 - Instrument Calibration
May 2007 - Adams Tannin Assay
April 2007- Laboratory Set-Up
March 2007- PCR Analysis
February 2007- ISO Accreditation