WINETECH Technical Yearbook 2019

them for SB wines, which saw a substantial increase in the green colour ( a* ) with temperature vs time. TAKE-HOME MESSAGE For the first time, a parallel study was done for Sauvignon blanc and Chenin blanc, with a focus on whether these two cultivars go through similar changes during storage. The changes reported in this study were over a nine month period of storage in conditions that varied from controlled to normal room temperature fluctuations that can be expected when a wine is on a shelf or at home. The results of the chemical evaluation of aroma and antioxidant-related parameters showed that the duration of storage has a great influence on a wine’s profile. The storage at higher temperatures creates less change in the wine when stored for shorter periods. The evolution of the chemical composition of the wines was

clear for most of the parameters considered (thiols and antioxidants), with time being the most relevant factor. Taking into account that six different Sauvignon blanc and Chenin blanc wines were used for the testing, we demonstrated that the evolution of the wines during storage was generally not dependent on the characteristics of the initial wine. In other words, regardless of the composition of the wine at time 0, the chemical changes were similar for most wines. Part 2 of the article will focus on the aroma changes that occurred during the testing period. SUMMARY Wine composition is susceptible to change due to oxidation that may occur during storage and transportation, especially at high temperatures. In a recent study at the

Department of Viticulture and Oenology of Stellenbosch University, we investigated changes in South African Sauvignon blanc and Chenin blanc wine sensory profile, volatile composition and antioxidant- related parameters, resulting from storage of unwooded wi nes under d i fferent temperatures (room temperature, 15°C and 25°C) and durations (0, 3 and 9 months). Statistical data analysis was used to assess the correlations in the sensory and chemical evolution of the wines relative to the control (time 0). REFERENCES Mafata, M., Stander, M., Thomachot, B. & Buica, A., 2018. Measuring thiols in single cultivar South African red wines using 4,4-dithiodipyridine (DTDP) derivatization and u l t rape r fo rman c e conve r gen c e chromatography-tandem mass spectrometry. Foods 7(9): 138. DOI: 10.3390/foods7090138.

Coetzee, C., Schulze, A., Mokwena, L., Du Toit, W.J. & Buica, A., 2018. Investigation of thiol levels in young commercial South African Sauvignon blanc and Chenin blanc wines using propiolate derivatization and GC-MS/MS. South African Journal of Enology and Viticulture 39(2): 180-184. Makhotkina, O., Pineau, B. & Kilmartin, P.A., 2012. Effect of storage temperature on the chemical composition and sensory profile of Sauvignon blanc wines. Australian Journal of Grape and Wine Research 18(1): 91-99. DOI: 10.1111/j.1755-0238.2011.00175.x. Pérez-Coello, M.S., González-Viñas, M.A., Garcia-Romero, E., Diaz-Maroto, M.C. & Cabezudo, M.D., 2003. Influence of storage temperature on the volatile compounds of young white wines. Food Control 14(5): 301- 306. DOI: 10.1016/S0956-7135(02)00094-4.

– For more information, contact Astrid Buica at abuica@sun.ac.za.