Growth and volatile phenol production by Brettanomyces bruxellensis in different grapevine varieties during fermentation and in finished wine

Abstract

Three red grapevine varieties, Touriga Nacional, Syrah and Cabernet Sauvignon, were evaluated for their susceptibility to spoilage by two strains of Brettanomyces bruxellensis during grape juice fermentation and in finished wine. B. bruxellensis ISA 2211 survived well during both alcoholic and malolactic fermentations. The 4-ethylphenol concentration at the end of malolactic fermentation was 176 µg L−1 for T. Nacional, 190 µg L−1 for C. Sauvignon and 149 µg L−1 for Syrah. These levels were slightly increased during 3 months of incubation, even though no culturable cells of B. bruxellensis could be detected after malolactic fermentation. However, a viable but non-culturable (VBNC) population of 3–4 log cells mL−1 was observed in all grape varieties when analyzed by flow cytometry. On the other hand, commercial varietal wines, inoculated with of B. bruxellensis ISA 1791, could attain levels of 6–8 log CFU mL−1 and 4-ethylphenol reached 1750, 1512 and 2707 µg L−1 in T. Nacional, C. Sauvignon and Syrah, respectively. Overall, the production of 4-ethylphenol was mostly dependent on the existence of growing B. bruxellensis populations, regardless of the grape variety. In finished wines, 4-ethylphenol was always produced in concentrations far above its preference threshold, indicating that T. Nacional, Syrah and C. Sauvignon are equally susceptible to the “horse sweat” taint.