Scientific principles for the sensory evaluation of wines can be difficult to implement in traditional sparkling wine (TSW), due to the wines’ complexity and effervescent nature.
The distinguishing feature about TSWs is the second alcoholic fermentation which creates its iconic effervescence. When it comes to sensory evaluations, the effervescence can be a bit of a challenge. Wines need to be tasted soon after pouring to preserve the bubbles, for sensory science this means that not that many wines can be tasted at once. Descriptive sensory analysis has been effectively used for the sensory evaluation of TSWs, but it can be costly. Sorting has previously been used on beer, which has a similar effervescence to TSW, but has only recently been used on MCC (South African TSW). Most of the flavour and aroma in TSWs comes from the second fermentation and yeast autolysis during ageing on the lees. Attributes related to yeast autolysis (creamy, toffee, oak, etcetera) are often high on the checklist for evaluating TSWs (Alexandre & Guilloux-Benatier, 2006).
Overview of the TSW winemaking process
TSW is produced from Chardonnay and Pinot noir in France, California, and Australia. The Spanish, Italians and Germans use native grape cultivars to produce their sparkling wines. South African winemakers use the same cultivars as in France and may occasionally use Chenin blanc and Pinot meunier. The traditional method of sparkling winemaking is referred to as méthode traditionnelle and méthode classique in French regions aside from Champagne, méthode champenoise in the Champagne region of France, metodo classico in Italy, and Méthode Cap Classique in South Africa.
Figure 1 illustrates the TSW winemaking process. Grapes are harvested early at a low berry sugar content between 17 and 20°B, whole-bunch pressed at low pressure (≤ 1.5 bars), the juice fermented at 12 to 15°C. A liqueur de tirage is added to sweetened base wines (20 to 24 g/ℓ sugar) and immediately bottled for the second fermentation. TSWs have to be riddled and disgorged off the lees in the same bottle that they are sold in. The minimum time of ageing of TSWs vary depending on national legislature, but is generally nine-months on lees. The dosage is added to dry TSW in order to give the wine more flavour and sweeten it to the winemakers’ preference. Brut sparkling wines (dry wines) require no dosage post disgorging (Zoecklein, 2002).
FIGURE 1. A flow diagram of the stages of the traditional sparkling winemaking process. The ageing period on the lees is dictated by national legislature. A dosage containing sugar and wine is added lastly, for taste.
Sensory evaluation of TSW
The TSW sensory experience is very different from table wines, due to the bubbles. Hood-White and Heymann (2015) used sensory descriptive analysis (DA) to assess the perceived intensity of aroma and effervescence. They found an optimal time of five minutes or less between pouring and tasting preserves the sensory experience of TSWs, in terms of aroma and mouthfeel.
DA is the most widely used sensory tool for wine analysis (TSW and table wines) and is very useful in terms of the amount of quantitative and qualitative data that may be generated. It gives both descriptors and their intensity. On the downside, it can be costly, time consuming, labour-intensive, require training and only a few wines may be assessed at a time (Hidalgo et al., 2004).
Directed and free-sorting methods, having previously been successfully done on beer, have only recently been performed in TSW. Sorting requires no training and allows for the rapid assessment of wines (Chollet et al., 2011). In a sorting exercise, a panel is given instructions to group wines according to a certain criteria, thus wines have to be assessed simultaneously. Directed sorting, where a panel is given a list of attributes, reduces panel fatigue and increases the number of wines assessed (Chollet et al., 2014).
The difficulty with sensory evaluation of TSW is the different vocabulary that judges use to communicate the attributes they perceive. In cases such as this, a free-sorting allows for the unrestricted generation of attributes from judges which can be narrowed down by a panel vocal discussion to reach consensus on similar attributes and grouping of attributes (Chollet et al., 2014).
Sensory characteristics of TSW
TSW flavour and aroma comes from the grapes, fermentation and ageing on lees. Grape-derived aroma attributes such as floral, fruity and herbaceous, are more present in younger TSWs (≤ nine months on lees). Aroma and taste attributes derived from ageing on lees include toasted bread, vanilla, caramel, woody, oak, liquorice and yeast autolytic character (Riu-Aumatell et al., 2013).
Yeast autolysis releases yeast cell products like polysaccharides, glycoproteins, lipids and nucleic acids (Martinez-Rodriguez et al., 2002). These products have a distinct sensorial character referred to as the “autolytic character” which has previously been associated with attributes such as toasty, bread, butter and butterscotch. The proteins released during yeast autolysis have previously been connected to the perception of ʻbodyʼ in TSW (Martinez-Rodriguez et al., 2002). Autolytic character is present in both young and old TSWs, but at different intensities.
Young TSW have aroma attributes such as fruitiness (exotic and citrus fruits), yeasty, floral, vegetal, yeasty, mould, reductive and oxidised notes (Pérez-Magarino et al., 2013). TSW aged older than nine months have attributes such as toasty, buttery, caramel and butterscotch (Francioli et al., 2003).
The classical DA method is still effective for evaluating TSW. The potential of sorting for TSW evaluation is promising as it is cost-effective and can be optimised to include descriptive information (directed sorting).
Results on a sorting exercise recently performed on MCC is available in Part 2 of this series (Do chilled grapes make better MCC?).
The authors would like to thank Winetech, THRIP and ARC-PDP for funding. The authors would also like to thank winemakers/cellarmasters/producers Craig Paulsen, Hannes Meyer, Pieter Ferreira and Charles Fox for assistance in the production of Cap Classique. Special thanks also to Dr Boredi Silas Chidi for his assistance throughout the project, as well as Prof Andrea Versari for his assistance with the proposal.
Alexandre, H. & Guilloux-Benatier, M., 2006. Yeast autolysis in sparkling wine – a review. Australian Journal of Grape and Wine Research 12, 119 – 127.
Chollet, S., Lelièvre, M., Abdi, H. & Valentin, D., 2011. Sort and beer: Everything you wanted to know about the sorting task, but did not dare to ask. Food Quality and Preference 22, 507 – 520.
Chollet, S., Valentin, D. & Abdi, H., 2014. Free sorting task. In: Novel techniques in sensory characterization and consumer profiling. Tomasso, P.V. & Ares, G. (Eds.), 207 – 227.
Francioli, S., Torrens, J., Riu-Aumatell, M., López-Tamames, E. & Buxaderas, S., 2003. Volatile compounds by SPME-GC as age markers of sparkling wines. American Journal of Enology and Viticulture 54(3), 158 – 162.
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Martínez-Rodríguez, A.J., Carrascosa, A.V., Martín-Àlvarez, P.J., Moreno-Arribas, M.V. & Polo, M.C., 2002. Influence of the yeast strain on the changes of the amino acids, peptides and proteins during sparkling wine production by the traditional method. Journal of Industrial Microbiology and Biotechnology 29, 314 – 322.
Pérez-Magarino, S., Ortega-Heras, M., Martínez-Lapuente, L., Guadalupe, Z. & Ayestarán, B., 2013. Multivariate analysis for the differentiation of sparkling wines elaborated from autochthonous Spanish grape varieties: Volatile compounds, amino acids and biogenic amines. European Food Research and Technology 236, 827 – 841.
Riu-Aumatell, M., Torrens, J., Buxaderas, S. & López-Tamames, E., 2013. Cava (Spanish sparkling wine) aroma: Composition and determination methods. Recent advances in pharmaceutical sciences, 3rd Ed., 45 – 60.
Zoecklein, B., 2002. A review of Méthode Champenoise production. Virginia Cooperative Extension.
– For more information, contact Francois van Jaarsveld at email@example.com.