WINETECH Technical Yearbook 2021

fermentation. Journal of Agricultural and Food Chemistry 61(15): 3703-3713. https:// doi.org/10.1021/jf3048753. Clark, A.C. & Deed, R.C., 2018. The chemical reaction of glutathione and trans -2-hexenal in grape juice media to form wine aroma precursors: The impact of pH, temperature, and sulfur dioxide. Journal of Agricultural and Food Chemistry 66(5): 1214-1221. https://doi.org/10.1021/acs.jafc.7b04991. OIV, 2015. Treatment of must wi th glutathione. Resolution OIV-OENO 445- 2015. Lyu, X., Del Prado, D.R., Araujo, L.D., Quek, S.-Y. & Kilmartin, P.A., 2021. Effect of glutathione addition at harvest on Sauvignon blanc wines. Australian Journal of Grape and Wine Research 27(4): 1-11. https://doi. org/10.1111/ajgw.12495.

Du Toit, W.J., Marais, J., Pretorius, I.S. & Du Toit, M., 2017. Oxygen in must and wine: A review. South African Journal of Enology and Viticulture 27(1): 76-94. https://doi. org/10.21548/27-1-1610. Tirelli, A., Fracassetti, D. & De Noni, I., 2010. Determination of reduced cysteine in oenological cel l wal l fract ions of Saccharomyces cerevisiae. Journal of Agricultural and Food Chemistry 58(8): 4565-4570. https://doi .org/10.1021/ jf904047u. Araujo, L.D., Vannevel, S., Buica, A., Callerot, S., Fedrizzi, B., Kilmartin, P.A. & Du Toit, W.J., 2017. Indications of the prominent role of elemental sulfur in the formation of the varietal thiol 3-mercaptohexanol in Sauvignon blanc wine. Food Research International 98: 79-86. https://doi . org/10.1016/j.foodres.2016.12.023. Harsch, M.J., Benkwitz, F., Frost, A., Colonna- Ceccaldi, B., Gardner, R.C. & Salmon, J.M., 2013. New precursor of 3-mercaptohexan- 1-ol in grape juice: Thiol-forming potential and kinetics during early stages of must

aroma compounds when added before pressing. More research is needed to investigate the exact benefits of these products. Especially when added just before fermentation as recommended by the suppliers, as opposed to adding the product prior to pressing where a large percentage of the product can potentially be removed with the grape skins. SUMMARY Glutathione, sulphur dioxide, ascorbic acid and commercial inactivated dry yeast products were added either in isolation or in combination, after which the volatile thiol content (among others) of the resulting wines were analysed. The addition of certain antioxidants led to significant and pronounced increases in 3MH and 3MHA, while others had no effect when compared to a control treatment. REFERENCES Herbst-Johnstone, M. , Nicolau, L. & Kilmartin, P.A., 2011. Stability of varietal

thiols in commercial Sauvignon blanc wines. American Journal of Enology and Viticulture 62(4): 495-502. https://doi.org/10.5344/ ajev.2011.11023. Penninckx, M., 2000. A short review on the role of glutathione in the response of yeasts to nutritional, environmental, and oxidative stresses. Enzyme and Microbial Technology 26(9-10): 737-742. https://doi.org/10.1016/ S0141-0229(00)00165-4. Salgues, M., Cheynier, V., Gunata, Z. & Wylde, R., 1986. Oxidation of grape juice 2-S-glutathionyl caffeoyl tartaric acid by Botrytis cinerea laccase and characterization of a new substance: 2,5-di-S-glutathionyl caffeoyl tartaric acid. Journal of Food Science 51(5): 1191-1194. https://doi. org/10.1111/j.1365-2621.1986.tb13081.x. Singleton, V.L. , Salgues, M. , Zaya, J. & Trousdale, E. , 1985. Caftaric acid disappearance and conversion to products of enzymic oxidation in grape must and wine. American Journal of Enology and Viticulture 36(1): 50-56.

For more information, contact Carien Coetzee at carien@basicwine.co.za.

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