WINETECH Technical Yearbook 2021

the aromatic profile compared to non- copper-treated wines. Besides a decrease in levels of varietal thiol 3MH in copper- treated wines, the increase in aromas of “peach” and “banana candy” was noticed. The copper addition altered the aromatic profile of Chenin blanc wine used in this experiment. However, we should not forget that “boiled egg” off-odour derived from excess H 2 S is far more detrimental to the perceived wine quality than a slightly altered aromatic profile of a wine. SUMMARY In Part 1 of this article series, we have shown the results of the short-term impact (after 24 hours and six weeks) of copper fining on a reductive Chenin blanc white wine that was naturally high in varietal thiols. In this second part, we report the long-term effects observed after one year

of storage. Using chemical and sensorial wine analysis, researchers from the South African Grape and Wine Research Institute (SAGWRI) (Stellenbosch University) carried out this novel project in collaboration with the researchers from the Australian Wine Research Institute (AWRI) in Adelaide. Contributing researchers: Marlize Bekker and Allie Kulcsar. REFERENCES Coetzee, C. & Du Toit, W.J., 2012. A compre - hensive review on Sauvignon blanc aroma with a focus on certain positive volatile thiols. Food Research International 45(1): 287-298. Wilson, C., 2017. Chemical evaluation and sensory relevance of thiols in South African Chenin blanc wines. Kreitman, G.Y., Elias, R.J., Jeffery, D.W. & Sacks, G.L., 2019. Loss and formation of

malodorous volatile sulfhydryl compounds during wine storage. Critical Reviews in Food Science and Nutrition 59: 1728-1752. Siebert, T.E., Solomon, M.R., Pollnitz, A.P. & Jeffery, D.W., 2010. Selective determination of volatile sulfur compounds in wine by gas chromatography with sulfur chemilumines- cence detection. Journal of Agricultural and Food Chemistry 58(17): 9454-9462. Clark, A.C., Grant-Preece, P., Cleghorn, N. & Scollary, G.R., 2015. Copper(II) addition to white wines containing hydrogen sulfide: Residual copper concentration and activity. Australian Journal of Grape and Wine Re­ search 21(1): 30-39. Ugliano, M., Kwiatkowski, M., Vidal, S. et al. , 2011. Evolution of 3-mercaptohexanol, hy- drogen sulfide, and methyl mercaptan during bottle storage of Sauvignon blanc wines. Effect of glutathione, copper, oxygen expo - sure, and closure-derived oxygen. Journal

of Agricultural and Food Chemistry 59(6): 2564-2572. Nikolantonaki, M. & Waterhouse, A.L., 2012. A method to quantify quinone reaction rates with wine relevant nucleophiles: A key to the understanding of oxidative loss of varietal thiols. Journal of Agricultural and Food Chemistry 60(34): 8484-8491. King, E.S., Osidacz, P., Curtin, C., Bastian, S.E.P. & Francis, I.L., 2011. Assessing desir - able levels of sensory properties in Sauvignon blanc wines – consumer preferences and contribution of key aroma compounds. Aus­ tralian Journal of Grape and Wine Research 17, 169-180.

For more information, contact Matija Leskovi ć at matija@sun.ac.za.

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