Can trellis affect the taste and mouthfeel of wines?
Some of the most important classes of compounds affected by bunch microclimate are non-volatiles such as phenolics, sugars and organic acids. Some of these compounds go through chemical transformations during winemaking (e.g. sugars during fermentation), while the presence of others is dependent on the winemaking protocols (e.g. extraction of phenolics depending on the skin contact and pressing). The nature and concentration of the non-volatiles in the grape at harvest will influence the wine composition, but sometimes the differences at harvest are not proportional to the ones in the final product.
In the previous article, we have presented results related to the aroma aspects of Chenin blanc wines made from various trellising systems; this time, the focus will be on the taste and mouthfeel (sensory) and non-volatile compounds (chemistry).
Taste and mouthfeel
The same panels assessed the aroma, taste and mouthfeel of wines: in 2017 industry professionals and an analytical panel, while in 2018 only the analytical panel. In the case of taste and mouthfeel, the panellists evaluated ‘body’ (full, medium and light), ‘complexity’ (complex and watery), ‘balance’ (balanced and unbalanced), ‘aftertaste’ (long, medium and short), and ‘aftertaste driven by’ (flavour, acidity, alcohol and bitterness).
The wines from similar trellis systems were perceived similarly by the two panels (2017). For both sets of results, there was a gradual change from one extreme (‘light body’, ‘short aftertaste’ and ‘unbalanced’ for Santorini) to a middle ground (‘balanced’, ‘medium aftertaste’, and ‘medium body’ for Smart-Dyson and Ballerina), then to the other end of the scale (‘full body’, ‘long aftertaste’ and ‘aftertaste driven by alcohol’ for T-frame). Lyre and Stok-by-paaltjie wines were placed between the ‘medium’ and ‘full’ categories.
Smart-Dyson and Ballerina systems are variants of each other, which indicate that the canopy exposure and the resulting chemistry may be comparable to each other and different from others. A similar scenario could be considered for the horizontal open canopies of T-frame and Lyre. Moreover, the Santorini system treatment falls under shaded canopies, clearly separated further away from the open canopy wines, and described by characters such as ‘light body’, ‘watery’ and ‘aftertaste driven by acidity’.
In 2018, the results (this time only from the analytical panel) were somewhat different from 2017. There was again a transition from ‘light’ to ‘medium’ to ‘full’; 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.1 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.2
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).3 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.
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.
The Central Analytical Facility at Stellenbosch University for the LC-HRMS work.
- 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 firstname.lastname@example.org.