WINETECH Technical Yearbook 2021

Santorini wines were once more placed in the first category, while Smart-Dyson, Lyre, and T-frame wines were in the ‘medium’ and ‘full’ side of the spectrum. However, Ballerina wines were perceived as ‘unbalanced’ and ‘bitter’. Grape berries exposed to sunlight are generally higher in sugars and phenolic compared to shaded (Morrison & Noble, 1990). The systems with open canopies and canopies which allow sunlight exposure (T-frame and Lyre) are expected to produce wines higher in sugars, therefore produce full body wines. The importance of balance in wine complements the aroma; highly acidic wines tend to be thin and watery with a dry perception (Conde et al ., 2007). CHEMICAL ANALYSES Vine training systems as tools to modify microclimate-related factors can affect wine matrix and contribute to differences in phenolic compounds that are responsible for taste and mouthfeel of wines. It was important to examine the wines using an approach that is more appropriate by including what targeted analysis could have omitted. Instead of looking for certain compounds linked in the literature with differences in bunch microclimate and light exposure, we took a different approach: we fingerprinted the wines using an untargeted

method aimed to non-volatiles, namely liquid chromatography coupled with high resolution mass spectrometry (LC-HRMS) (Panzeri et al ., 2020). Indeed, the fingerprints for the wines indicated that the samples could be separated according to trellising systems. Information-rich techniques such as LC- HRMS could be the answer to complex scenarios. The results indeed indicated that wine samples differed according to treatment, in a similar grouping pattern as the taste and mouthfeel results. Even though it is not clear which chemical compounds were responsible for the groupings, we hypothesised that sample composition prompted the similarities and differences in profiles (especially the phenolics, which are one of the main groups of compounds detected by LC-HRMS). TAKE-HOME MESSAGE Chenin blanc wines made from six different trellising systems were evaluated chemically and sensorially. Besides yield, the synthesis and evolution of chemical compounds may be altered by vine architecture, and this was the core subject of the current study. In contrast to aroma (results presented in the previous article), the taste and mouthfeel of the wines varied consistently between the trellising systems and the results were supported by the

chemical analysis performed. Taste and mouthfeel were more prominently affected as the systems have an impact on phenolic compounds responsible for mouthfeel and on other compounds such as sugar levels at harvest correlated to alcohol levels in resulting wines. The differences in taste and mouthfeel further played a role in the wines’ quality scores. Santorini system wines were associated with negative attributes: ‘acidity’, ‘light body’, ‘watery’, and ‘short after taste’ and scored the lowest. In brief, with trellising systems there is ‘no one size fits all’. Under the same conditions in the same vineyard, there were differences in relevant aspects related to wine taste, mouthfeel and quality, but not aroma. These results should be carefully considered before extrapolating them to wines from a vineyard with a different terroir and more specifically to wines from a different cultivar. Particularly in the light of climate change, drought, and consumers requiring lower alcohol wines, choosing a trellis should be based on the objectives of the winemaker, but should not underrate the significance of consumer preference and economic factors. SUMMARY The grapevine’s response to a treatment or to a set of imposed conditions is the result of a series of interactions between genetic

characteristics, environmental conditions and viticultural practices. As such, grape composition can be influenced by vineyard practices. Maybe even more relevant to the producer is how changes in the berry composition translate into the chemical and sensory properties of the final wines. ACKNOWLEDGEMENT The Central Analytical Facility at Stellen - bosch University for the LC-HRMS work. REFERENCES Morrison, J. & Noble, A., 1990. The effects of leaf and cluster shading on the composition of Cabernet Sauvignon grapes and on fruit and wine sensory properties. American Journal of Enology and Viticulture 41: 193-200. Conde, C., Silva, P., Fontes, N., Dias, A.C.P., Tavares, R.M., Sousa, M.J., Agasse, A., Delrot, S. & Gerós, H., 2007. Biochemical changes throughout grape berry development and fruit and wine quality. Food : 1-22. Panzeri, V., Iipinge, H.N. & Buica, A., 2020. Evaluation of South African Chenin blanc wines made from six different trellising systems using a chemical and sensorial approach. South African Journal of Enology and Viticulture 41: 133-150. For more information, contact Astrid Buica at astrid.buica@gmail.com.

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