WINETECH Technical Yearbook 2019

strategies in a Shiraz winemaking trial. Standard oenological parameters, volatile composition and sensory attributes were investigated. Wines produced with non- Saccharomyces yeasts had lower alcohol and glycerol levels than the reference wines produced with only Saccharomyces cerevisiae , and the duration of malolactic fermentation was also shorter. Non- Saccharomyces wines also differed chemically and sensorially from wines produced with only S. cerevisiae. The Candida zemplinina and one of the Lachancea thermotolerans isolates slightly inhibited LAB growth in wines that underwent simultaneous MLF. Generally, MLF strategy had a greater impact on wine sensory attributes than yeast treatment. Both yeast selection and MLF strategy had a significant effect on berry aroma of wines,

but MLF strategy also had a significant effect on acid balance and the perceived astringency. By selecting and applying the correct yeast combination and MLF strategy winemakers can ensure rapid completion of MLF and improved wine complexity. ACKNOWLEDGEMENTS The authors thank the Agricultural Research Counc i l , Wi netech and the Nat i ona l Research Foundation of South Africa (THRIP programme; grant numbers UID 71526 and 90103) for funding, and Justin Hoff, Chrizaan du Plessis, Philda Adonis, Sonia Podgorski and Robyn-Lee Louw are thanked for technical assistance. The opinions, findings and conclusions expressed in this publication are those of the authors. The National Research Foundation accepts no liability in this regard.

Swiegers, J.H., Bartowsky, E.J., Henschke, P.A. & Pretorius, I.S., 2005. Yeast and bacterial modulation of wine aroma and flavor. Australian Journal of Grape and Wine Research 11, 139-173. Alexandre, H., Costello, P.J., Remize, F., Guzzo, J. & Guilloux-Benatier, M., 2004. Saccharomyces cerevisiae-Oenococcus oeni interactions in wine: Current knowledge and perspectives. International Journal of Food Microbiology 93, 141-154. Du Plessis, H.W., Du Toit, M., Hoff, J.W., Hart, R.S., Ndimba, B.K. & Jolly, N.P., 2017. Characterisation of non- Saccharomyces yeasts using different methodologies and evaluation of their compatibility with malolactic fermentation. South African Journal of Enology and Viticulture 38, 46-63.

REFERENCES May r, C .M. , Geue , J . P. , Ho l t , H . E . , Pearson, W.P., Jeffery, D.W. & Francis, I.L., 2014. Characterization of the key aroma compounds in Shiraz wine by quantitation, aroma reconstitution, and omission studies. Journal of Agricultural and Food Chemistry 62, 4528-4536. 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. Bartowsky, E.J., Costello, P.J. & Chambers, P.J., 2015. Emerging trends in the application of malolactic fermentation. Australian Journal of Grape and Wine Research 21, 663-669.

– For more information, contact Heinrich du Plessis at dplessishe@arc.agric.za.