WINETECH Technical Yearbook 2019

had amongst the lowest sensory scores of all the wines. SMALL-SCALE PINOTAGE VINIFICATIONS The Pinotage fermentations were all completed within five days. In contrast to the Chenin blanc fermentations, all the T. delbrueckii single inoculated treatments fermented dry (under 4 g /L residual sugar). However, the contribution by the S. cerevisiae natural population cannot be discounted as the red wine production process is more susceptible to contamination by resident S. cerevisiae cellar populations. In the Pinotage wines, there was also no indication that the T. delbrueckii contributed to higher total SO 2 levels. Overall, the sensory results showed no notable differences between the wines. This therefore reinforces the observation that T. delbrueckii may have been out-dominated by the growth of the natural S. cerevisiae background resident population and so no T. delbrueckii imprint is evident. CONCLUSIONS The various co-inoculation treatments all led to dry wines, and in the Chenin blanc, a T. delbrueckii chemical and sensory imprint was evident. A similar imprint was

not observed in the Pinotage wines. From the results obtained, two South African T. delbrueckii isolates showed potential as single inoculant yeasts for commercial Chenin blanc production. SUMMARY T. delbrueckii and S. cerevisiae yeast were used for the production of Chenin blanc and Pinotage wines at 15 and 24ºC, respectively. The T. delbrueckii yeasts were used either as single inoculants, or as co-inoculants with the commercial S. cerevisiae yeast. The S. cerevisiae yeast was added at zero, 24 or 48 hours after the T. delbrueckii strain. Results for the Chenin blanc trial showed that two of the South African T. delbrueckii yeasts had a positive effect on the wine’s chemical and sensory profile. These wines were of a higher quality than those of the S. cerevisiae reference treatment. Results of the Pinotage vinifications were less conclusive and no distinctive T. delbrueckii effect could be found in the chemical and sensory data. ACKNOWLEDGEMENTS The authors wish to thank the ARC Infruitec- Nietvoorbij and Winetech for financial support and the Microbiology team for technical assistance.

Jolly, N.P., Augustyn, O.P.H. & Pretorius, I.S., 2003B. The effect of non- Saccharomyces yeasts on fermentation and wine quality. South African Journal of Enology and Viticulture 24, 55-62. Lerm, E., Engelbrecht, L. & Du Toit, M., 2010. Malolactic fermentation: The ABC’s of MLF. South African Journal of Enology and Viticulture 31, 186-212. Bely, M., Stoeckle, P., Masneuf-Pomarède, I. & Dubourdieu, D., 2008. Impact of mixed Torulaspora delbrueckii-Saccharomyces c e r e v i s i a e c u l t u r e o n h i g h - s u g a r fermentation. International Journal of Food Microbiology 122, 312-320. Minnaar, P.P., Ntushelo, N., Ngqumba, Z., Van Breda, V. & Jolly, N.P., 2015. The effect of Saccharomyces cerevisiae and Torulaspora delbrueckii yeasts on the anthocyanins and flavanols of Cabernet franc and Pinotage wines. South African Journal of Enology and Viticulture 36, 50-58. Ngqumba, Z., Ntushelo, N., Jolly, N.P., Ximba, B.J. & Minnaar, P.P., 2017. Effect of Torulaspora delbrueckii yeast treatment on flavanols and phenolic acids of Chenin blanc wines. South African Journal of Enology and Viticulture 38, 192-200.

REFERENCES Jolly, N.P., Varela, C. & Pretorius, I.S., 2014. Not your ordinary yeast: Non- Saccharomyces yeasts in wine production uncovered. FEMS Yeast Research 14, 215-237. Van Breda, V., Jolly, N. & Van Wyk, J., 2013. Characterisation of commercial and natural Torulaspora delbrueckii wine yeast strains. International Journal of Food Microbiology 163, 80-88. Van Breda, V., Jolly, N.P., Booyse, M. & Van Wyk, J., 2018. Torulaspora delbrueckii yeast strains for the production of small-scale Chenin blanc and Pinotage wines. South African Journal of Enology and Viticulture 39, 47-57. Jolly, N.P., Augustyn, O.P.H. & Pretorius, I . S . , 2003A. The occur rence of non- Saccharomyces cerevisiae yeast strains over three vintages in four vineyards and grape musts from four production regions of the Western Cape, South Africa. South African Journal of Enology and Viticulture 24, 35-42. Ciani, M. & Maccarelli, F., 1998. Oenological properties of non- Saccharomyces yeasts associated with winemaking. World Journal of Microbiology and Biotechnology 14, 199-203.

– For more information, contact Neil Jolly at jollyn@arc.agric.za.