South Africa Wine Technical Yearbook 2025

TABLE 1. Volatile phenol descriptions and thresholds. Molecule Default

fermenting musts. They showed that isolates from the vineyard and winery represented dominant and common biotypes, which indicated that vineyards are a contamination source of B. bruxellensis in the winery environment. Lately, Pigao and other authors (2021) also isolated Brettanomyces bruxellensis from 12 of 149 grape clusters (two years sampling) in a vineyard in Oregon. Currently, bioprotection solutions with non- Saccharomyces yeasts in the pre-fermentative steps exist, but they are not really effective against Brettanomyces . 3. A new non- Saccharomyces selection: LEVEL 2 SALVA™ Suhomyces pyralidae (formerly Candida pyralidae ) IWBT Y1140 was isolated from South African Cabernet Sauvignon grape juice (Mehlomakulu et al. , 2014). by the South African Grape and Wine Research Institute (University of Stellenbosch). It was shown to control and inhibit B. bruxellensis strains found in the wine environment. It is now available to wine producers under the name LEVEL 2 SALVA™. This specific inhibiting activity is explained by the production of a Brettanomyces Inhibition Factor,

Concentration/ perception in wine

4-ethylphenol 4-ethylguaiacol 4-vinylphenol 4-vinylguaiacol

Barnyard, stable

500 µg/L 100 µg/L

Clove

Band-aid Band-aid

1 500 µg/L

400 µg/L

Brettanomyces bruxellensis can be found at different stages of the winemaking process. It can also be present in vineyards, even on specific blocks within a vineyard. Previous studies have established the presence of Brettanomyces bruxellensis in several vineyards at various stages of grape development following veraison. (Renouf et al. , 2007). 1. Classical control against Brettanomyces The most common tool to avoid Brettanomyces bruxellensis contamination is SO 2 addition. However, according to Avramova and other authors (2018), adaptation phenomena led to a Brettanomyces bruxellensis subpopulation that is resistant to SO 2 . With the tendency to decrease inputs, including sulphites, it is important to find alternative solutions to prevent and inhibit B. bruxellensis development during wine production and storage, in

addition to considering this potential SO 2 resistance. 2. The interest of controlling Brettanomyces in the pre fermentative steps As Brettanomyces is also found before the onset of fermentation, a preventive approach is needed to inhibit and control it by using bioprotection. They are found on grapes, even before the vinification process, as demonstrated by Renouf and Lonvaud-Funel (2007), who detected it in samples taken in four vineyards from the Bordeaux area at different development stages of the grape between veraison and harvest. Oro and other authors (2019) proved the strict relationship between Brettanomyces bruxellensis strains from the vineyard and from the winery with molecular analysis (26S-D1/D2 region of rDNA sequencing) of 62 samples from grapes, winery environments and

FIGURE 1. Viability during red grape juice (pH 3,5) fermentation at 20°C. 1.A shows the evolution of population in mono-culture of Brettanomyces bruxellensis , LEVEL 2 SALVA™ and Saccharomyces cerevisiae. 1.B shows the evolution of population in co-culture.

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TECHNICAL YEARBOOK 2025