French Winemakers Embrace Inactive Yeast for Cellar Flexibility

French winemakers are increasingly turning to inactive dry yeast preparations as a flexible tool in the cellar, using them to feed fermentations, limit oxidation, support malolactic conversion and, in some cases, stand in for lees during aging.

The products, known in French as levures sèches inactivées, or LSI, are not a single ingredient but a broad category of yeast-derived aids made through different production methods and from different strains. Some are produced by heat shock, others by changes in pH or high pressure. Newer versions also use non-Saccharomyces yeasts, widening their possible uses. That variety has made the category harder to read for winemakers, even as demand grows for tools that can help manage more difficult harvests and tighter production conditions.

According to the International Organisation of Vine and Wine, inactive yeasts can be used as nutrients for active yeasts at the start and during alcoholic fermentation, and they can also help with rehydration of active dry yeast. They may reduce ochratoxin A during élevage and clarification. In Europe, the regulatory framework has also placed them under a broader “other practices” category, which gives producers more room to use them across the life of the wine.

That flexibility is one reason suppliers describe LSI as a kind of oenological Swiss Army knife. Stéphane La Guerche, chief executive of Œnoppia, said the European interpretation allows their use at almost any stage. The products are considered technological aids rather than additives, which means they do not require labeling in the same way as gum arabic or mannoproteins. They are also natural in origin, nonallergenic and suitable for organic production and NOP standards, except for certain products with guaranteed glutathione content.

Their first role is often nutritional. Annabelle Cottet, product manager for yeasts and derivatives at Œnobrands, said inactive dry yeast provides organic nitrogen that is “twice as nourishing” as mineral nitrogen and is allowed in organic winemaking. Depending on whether they are used alone or with other inputs such as mineral nitrogen or thiamine, they may be added at the beginning of fermentation or about one-third of the way through it.

Manufacturers say composition matters because different products are designed for different wine styles. Charlotte Vion of Laffort’s development and innovation team said some LSI products contain higher lipid levels for sparkling wines, while others have more reducing compounds for white and rosé wines. André Fuster, technical manager at AEB, said his company studied amino acid profiles in grape varieties and found that they follow a characteristic pattern at maturity. Because amino acids can be aroma precursors, AEB developed activators that mimic the amino acid profile of aromatic grapes to steer yeast metabolism toward desired aromas.

Some LSI products are also selected for their glutathione content, which can help protect must and wine from oxidation when added early in fermentation. The effect begins quickly and can continue into the finished wine, though producers say these products are not meant to serve as long-term preservatives.

Inactive yeast preparations are also being used to support malolactic fermentation. Unlike yeast, Oenococcus oeni prefers peptides. At least three peptide-rich LSI formulations have been developed to help start or speed up malolactic conversion, including Maloboost, Maxaferm MLForce and Opti ML. Producers say these products can be useful after a sluggish alcoholic fermentation or when malolactic fermentation needs restarting under difficult conditions such as high alcohol levels, low temperatures, low turbidity or a lack of lees.

Another use is to mimic the contribution of lees during aging without some of the risks associated with natural lees. When added during élevage instead of or alongside original lees, LSI can provide a guaranteed level of compounds of interest. Galdric Nogues, technical director at Lamothe-Abiet, said that if brettanomyces contamination is suspected, inactive yeasts can replace lees after proper cleanup. Olivier Pillet, who oversees product development at IOC, said some effects can appear within five days, giving winemakers time to test results before committing further. Because the yeasts are inactive, they do not trigger sulfite reductase activity that could create sulfur odors during aging. Their effects are also more reproducible than those of lees.

Price remains relatively accessible by cellar standards. LSI generally sell for 25 to 35 euros per kilogram and are used at rates of 10 to 40 grams per hectoliter. That puts their cost at roughly 0.30 to 1 euro per hectoliter, though prices rise when products include ingredients such as grape skins or mannoproteins that are more expensive to produce.

Winemakers looking at the market are advised to read labels closely and check whether a product contains only inactive yeast or a blend with other materials. Some formulations are meant for all wine styles; others target specific problems that continue to expand as producers seek more precise cellar tools. Recent examples include Optifine lees from Lamothe-Abiet, which combines inactive yeast with pea protein, and Caudalys from IOC, a non-Saccharomyces LSI designed to improve mouthfeel length.

The category is still easy to confuse with other yeast derivatives. Autolyzed yeasts are dead cells whose contents are accessible; yeast hulls contain only cell membranes; mannoproteins make up part of those membranes; inactive dry yeasts are whole dead cells. For producers trying to manage fermentation risk, oxidation and aging consistency at once, that distinction matters as much as the label on the bag.