Issue link: http://winesandvines.uberflip.com/i/840286
July 2017 WINES&VINES 57 WINEMAKING In most spontaneous fermentations, S. cerevisiae naturally present (though initially at very low numbers) in the must will eventually dominate and complete the fermentation. If this progression does not occur, and warning signs of a slowing fermentation appear, it be- comes necessary to take remedial action im- mediately and rescue the must with a commercial wine yeast strain. If not, spoilage micro-organisms can start to proliferate and form off-odors such as volatile acidity (LAB) and vinyl and ethyl phenols (Brettanomyces). The commercial yeast dosage added will depend on the level of residual sugar and al- cohol concentration. It can be up to double the normal recommended dosage for an inoculated fermentation. The lower the sugar and the higher the alcohol, the higher the yeast dosage needed to complete a fermentation. It is important that commercial yeast is also gradually acclimatized to the alcohol level in sluggish wine before being intro- duced to the wine. A proper re-inoculation strategy should be followed, starting with full analytical analysis of the sluggish/stuck wine as well as detoxification with yeast hulls before re-inoculation with commercial yeast. It is important that the temperature is conducive to re-inoculation. Conclusion Spontaneous fermentations may be fashion- able today, but the same risks still exist as in the past. Executing a successful spontaneous fermentation requires greater scientific knowl- edge compared to inoculated fermentation. While less intervention in the form of culture inoculations is required, the management of a spontaneous fermentation is more intensive and relies on a solid knowledge base regarding yeast management. Research in the field of microbial diversity analysis, microbial interactions, nutrition and control of non-Saccharomyces yeasts at the Institute for Wine Biotechnology (Stellenbosch University) is ongoing and will assist winemak- ers to conduct spontaneous fermentations in an informed fashion. While certain grape varieties, winemak- ing conditions, wine styles and price points lend themselves to spontaneous fermenta- tions, there are also times when inoculation with a selected yeast culture remains the better option. Debra Rossouw is a researcher in yeast molecular biology at Stellenbosch University (Institute for Wine Biotechnol- ogy). She works with S. cerevisiae, non-Saccharomyces yeasts and lactic acid bacteria. She is interested in mi- crobial interactions, cell walls and flocculation as well as aroma metabolism. The references for this article are available online at winesandvines.com. TTB LABEL APPROVALS Low per-label costs Gov't. Liaison Negotiations or Footwork Reasonable Hourly Rates TRADEMARK SEARCHES As Low as $185 Your trade names or designs are searched at the U.S. Patent Office to help establish valuable ownership or avoid costly legal liability. Over 100 years' total staff experience handling every government liaison need for industry. Phone or write for details. 200 N. Glebe Rd., Suite 321 Arlington, Virginia 22203 Phone: (703) 524-8200 Fax: 525-8451 TOLL-FREE 1-800-642-6564 Major Credit Cards Accepted www.trademarkinfo.com Since 1957 GovtLiaison_Dir08 11/29/07 2:00 PM Pag Toll-Free: 877-552-4828 909-464-1373 • Fax: 909-464-1603 For your nearest dealer, contact: BRANCHLOK™ Used for lateral training of trellised branches and cordons to 12-14 gauge wire. Branchlok™ is available in three lengths: 2½", 3¼", 3 ¾". Patent No. 4,665,000 WineVineBranchLokAD.qxp_Layout 1 12/1/14 2:46