Commercial Yeast Inoculation: Selected Strains and Their Character

Commercial yeast inoculation is the addition of a measured dose of selected, commercially produced yeast to juice or must, so that a chosen strain conducts the alcoholic fermentation rather than the natural microflora present on the grapes or in the winery. Yeast in wine is commonly associated with the species Saccharomyces cerevisiae, and cultivated strains were originally isolated from ambient yeasts. More than 200 strains are commercially available for winemaking. Traditionally these have been strains of S. cerevisiae, but yeast breeding research has made new hybrid strains available, such as AWRI2526, which is sold commercially by AB Biotek and was developed to add flavour and aroma complexity to wines. Suppliers also sell non-Saccharomyces species: Lallemand's LEVEL range includes pure cultures of Torulaspora delbrueckii and Lachancea thermotolerans, each used in sequential inoculation ahead of a Saccharomyces cerevisiae yeast.

• A generic inoculation rate for active dry wine yeast (ADWY) is 0.25 g/L (25 g/hL) of juice; high solids musts are typically inoculated at 0.20 g/kg (approximately 20 g/hL) because of their smaller liquid volume.
• The dosage rate for LALVIN EC1118, 71B, QA23 and RC212 is 20 to 40 g/hL.
• In Lallemand's words, EC1118 is considered by many to be the universal yeast, and its fast implantation efficiently controls the indigenous microflora.

Yeasts are single-cell microorganisms responsible for the enzymes that convert six-carbon sugar molecules into ethyl alcohol and carbon dioxide while releasing heat, and they also produce small amounts of volatile compounds, such as esters, aldehydes and sulphur, that contribute to a wine's aroma and flavour. In an uninoculated ferment, non-Saccharomyces yeasts dominate the early stages, whereas the majority of the alcoholic fermentation is conducted by Saccharomyces yeast. Non-Saccharomyces wild yeasts tend to give way to S. cerevisiae when alcohol in the must goes significantly higher than 5% abv, or when there is enough sulphur dioxide to restrict them. The juice or must should equal or exceed 15°C when inoculated, to advantage the yeast culture over indigenous strains, and active fermentation typically initiates within 24 hours. Nitrogen affects the rate and completion of fermentation: there is a direct relationship between yeast assimilable nitrogen (YAN) levels, yeast cell growth and fermentation rate, and yeasts vary in their nitrogen requirements, with low, medium and high nitrogen demand strains.

• If a strain's nitrogen requirement is not met, this can lead to sluggish or stuck fermentations and in turn to off-flavours and winemaking faults; the AWRI provides a calculator for diammonium phosphate (DAP) additions to increase YAN.
• Once active fermentation begins, temperature changes exceeding 3-5°C per day may partially inactivate budding yeast.
• Each strain has a competitive 'Killer K2' factor status: active for EC1118 and QA23, neutral for RC212 and sensitive for 71B.

Different strains produce different aroma and flavour compounds, and Benjamin Lewin MW has pointed out that the influence of yeasts is most evident in aromatic wines, because 'small changes in the concentrations of key components can greatly affect varietal character'. LALVIN 71B is a high ester producer, mainly isoamyl acetate, and the banana notes of Beaujolais Nouveau are believed to come from isoamyl acetate formed by strain 71B. 71B can metabolize a portion of the malic acid in musts, between 20 and 40% of it, softening the wine palate. LALVIN QA23 has a very high β-glucosidase activity, which cleaves non-volatile aromatic compounds into their volatile state; Lallemand calls it a proven thiol converter, highly recommended for Sauvignon Blanc, and credits it with enhancing citrus fruit aromas including lime and grapefruit. In Lallemand's account, LALVIN RC212 helps produce Pinot Noir with structure, ripe cherry, bright fruit and spicy characters and, compared to other yeast recommended for Pinot Noir, gives greater anthocyanin content and higher color intensity because of the limited adsorption of polyphenols on its cell walls.

• Lallemand highly recommends QA23 for varieties rich in terpenes, such as Riesling, since many terpenes are bound to glucosides.
• 71B adsorbs a part of the polyphenolic compounds on its cell wall, limiting the harshness of the tannic structure of primeur red wines.
• The CY3079 yeast can increase the hazelnut and brioche notes of Chardonnay.

The choice between ambient ('wild') yeasts and cultivated strains is one of the most controversial subjects in winemaking. The case for inoculation is risk control. One of the main risks of uninoculated fermentation is high levels of acetic acid or ethyl acetate forming early in the ferment, produced by Hansenula and Kloeckera spp., which may dominate ferments early when no SO2 is present, and uninoculated fermentation is not advisable in years with significant disease pressure. Naturally existing yeasts also carry the risk of unwanted strains such as Brettanomyces, wild Saccharomyces yeasts can be ineffective and unpredictable, and many modern winemaking operations choose pre-selected yeast strains to ensure a smoother, more controlled fermentation. On the other side, defenders of wild fermentation argue that a single cultured strain leads to somewhat artificial flavours or a lack of diversity between wines; some winemakers instead experiment with blends of cultured yeasts. Effective rehydration of active dry wine yeast is paramount in obtaining a healthy and viable inoculum, and the generic procedure is to pre-heat water to 38-40°C, sprinkle the yeast slowly and evenly over 5-10 times its weight in water, avoid clumps, and then cool the culture slowly to within 5-10°C of the juice or must, in steps of 5-10°C over a period of 10-20 minutes.

• The manufacturer's instructions should be followed first; Lallemand's LALVIN datasheets specify rehydration in 10 times the yeast's weight in water at 35 °C to 40 °C, a 20 minute wait, and a total rehydration time not exceeding 45 minutes.
• For highly clarified juices, high °Brix/°Baume musts or musts with inhibitory residual SO2, a higher inoculum may be used at up to twice the normal rate.
• Lallemand recommends one of its GO-FERM yeast protectors during rehydration for musts with high alcohol potential (above 13% v/v), low turbidity (below 80 NTU) or other challenging conditions.
• When water alone is used for rehydration, the yeast should be inoculated immediately once the cooling steps are complete, to avoid inactivation of the cells.

Four LALVIN strains from Lallemand illustrate the range. EC1118 was isolated from nature in the French region of high-quality sparkling wine; it has an optimum fermentation temperature range of 10 to 30 °C, alcohol tolerance up to 18% v/v, a short lag phase and a high fermentation rate, and Lallemand highly recommends it for sparkling secondary fermentation and recommends it for white, rosé and red wine production. 71B was isolated by INRAe (National Agricultural Research Institute) in Narbonne, France; Lallemand bills it as the yeast for primeur and fruity young wines, and it has an optimum range of 15 to 30 °C and alcohol tolerance up to 14% v/v. RC212, also called Bourgorouge, was selected from nature by the BIVB for its ability to ferment a traditional heavier style Burgundian Pinot Noir; Lallemand calls it the 'reference' strain for the production of quality Pinot Noir worldwide, and it has an optimum range of 18-30°C and alcohol tolerance up to 16% v/v. QA23 was selected in Portugal's Vinhos Verdes region by the University of Tras os Montes e Alto Douro (UTAD) in co-operation with the Viticultural Commission of the Region Vinhos Verdes; it has an optimum range of 14 to 28 °C and alcohol tolerance up to 16% v/v.

• Lallemand credits EC1118 with an elegant and low impact sensory profile, allowing its use for sparkling, white and red wines.
• RC212 enhances the polyphenolic content of grape types such as Pinot Noir, Grenache, Gamay and Zinfandel.
• Lallemand calls QA23 a very reliable, clean fermenter that tends to ferment well with a low VA production even in clarified juice low in nutrients.

Nitrogen is a critical practical consideration when choosing a strain: it is important to know the YAN concentration in the must prior to fermentation and to understand the nitrogen demand of the chosen yeast. The other parameters vary widely from strain to strain. Alcohol tolerance runs from up to 14% v/v for 71B, to up to 16% v/v for QA23 and RC212, to up to 18% v/v for EC1118, while LEVEL2 LAKTIA, a Lachancea thermotolerans culture, has an alcohol tolerance below 10% v/v and is used in sequential inoculation with a Saccharomyces cerevisiae yeast. 71B has a very low nutritional requirement, QA23 a very low nutritional requirement at any temperature from 18 to 28 °C, EC1118 a low relative nutritional requirement and RC212 an average nutritional requirement. For acidity, LEVEL2 LAKTIA helps re-equilibrate the acidity of wines, especially those from hot climates, thanks to a significant by-production of lactic acid; the second inoculation with Saccharomyces cerevisiae follows after 24 to 72 hours, and delaying it leads to increased lactic acid production. LEVEL BIODIVA, a Torulaspora delbrueckii culture, is selected to enhance aromatic and mouthfeel complexity, with the Saccharomyces cerevisiae inoculation following a density drop of 10 to 15 points (1.5 to 4°Brix).

• LEVEL BIODIVA's low volatile acid production and tolerance to osmotic shock make it particularly well-adapted for fermenting late harvest and ice wines.
• LEVEL2 LAKTIA has high nitrogen requirements and high glycerol production.
• Both LEVEL cultures call for a free SO2 level lower than 15 mg/L in white wines before inoculation, and a 25 g/hL dose rehydrated in water between 20 °C and 30 °C.

Primary sources (the Australian Wine Research Institute, and Lallemand Oenology's own technical datasheets for its own strains): https://www.awri.com.au/industry_support/winemaking_resources/wine_fermentation/yeast-rehydration/, https://www.awri.com.au/industry_support/winemaking_resources/winemaking-practices/winemaking-treatment-yeast-choice/, https://products.lallemandwine.com/storage/files/wine-yeasts/139-technical-datasheet-cp-1711100448.pdf, https://products.lallemandwine.com/storage/files/wine-yeasts/191-technical-datasheet-cp-1711125142.pdf, https://products.lallemandwine.com/storage/files/wine-yeasts/145-technical-datasheet-cp-1711101134.pdf, https://products.lallemandwine.com/storage/files/wine-yeasts/148-technical-datasheet-cp-1711101955.pdf, https://products.lallemandwine.com/storage/files/wine-yeasts/170-technical-datasheet-us-1733841051.pdf, https://products.lallemandwine.com/storage/files/wine-yeasts/224-technical-datasheet-us-1733842997.pdf. Secondary: https://www.decanter.com/learn/wine-yeast-45474/. Last verified 2026-10-04