Moderator : Gabriel Lepousez
3. Pascal Poupault - Expert panel, textual method and chemical markers to characterize the aromatic components of Chenin Blanc in the Loire Valley
To assess viticultural and oenological practices, a method was implemented to characterise wine profile in a relevant and objective way. It consists of association between chemical markers and aroma described to obtain a consensus on sensory profile description. Chemical markers (a thiol, C13-norisoprenoid, three esters or fermentation acetate) of Chenin were identified from sampling of wines made in Loire Valley. Theses markers are characteristic of Chenin wines, and of its different profiles (all the AOP of Loire Valley).
A jury is trained to recognise these markers and aromas derived from theses markers. This training leads to a package of descriptors used by the jury to describe aromas. The categorisation of these descriptors leads to a wanted consensus to characterise aromas families required to describe sensory profile of the wines.
The result is the acquisition of a jury trained to recognise different aroma families. These families are linked, in an objective and consensual way, to aromatic components constitutive of the sensory profiles of Chenin wines: vegetal, floral and fruity characters. Sensory impact of viticultural and oenological practices can be evaluated thanks to applied research programs, initiated by inter-professional association of Loire Valley winemakers (Interloire) and FranceAgriMer.
This work also build a tool to discuss tastes of Chenin wine and aim an international language for this multi-faceted variety.
Session VI - Taste, tastes of Chenin blanc wines
4. Dr. Astrid Buica with Dr. Jeanne Brand, Ms. Mpho Mafata et Ms. Valeria Panzeri as co-auhors - Towards demonstrating the concept of `old vine character´ for South African Chenin Blanc wines
In an effort to preserve and promote the value of South African “old vines”, research initiatives have been put into action at Stellenbosch University.
One of them has as focus elucidating the views industry experts have with regards to old vine wines. Even though South African vineyards are still young compared to European standards, there is a belief that vines aged 35+ years produce grapes and wines with specific characteristics.
In this study, the first aim was to address the existence of the concept of “old vine character” using a multifaceted approach. Wines were made from grapes from various age vineyards (5-45 years) but with the same winemaking practices. Industry experts were asked to evaluate the wines in a series of exercises that challenged their knowledge and preconceptions. The exercises varied from non-verbal (rating the wines presented on a scale from “none” to “typical of old vine character”), to a free word association (what comes to mind if we say “old vine character”?), followed by a directed sorting (plus descriptors) of the wines into “young vine” and “old vine” groups. The increase in task complexity and verbalisation allowed us to work towards demonstrating the existence of a rather unified “old vine character” concept and that this concept is defined by the industry experts’ previous knowledge (top-down process) and by the wines presented to them (bottom-up process).
These results are part of an extensive work also looking into chemical markers of the “old vine character”, based on the findings of the sensory work.
5. Dr. Astrid Buica with Dr. Jeanne Brand as co-author - The role of thiols in South African Chenin Blanc wines
The classes of compounds contributing to the aroma of Chenin Blanc wines have been described in various studies. The complexity of the analytical methods matched the difficulty of determining certain compounds.
Amongst these, thiols play a significant role in South African Chenin Blanc wines, as demonstrated in recent years in sensory and chemistry studies. In addition to showing how some vineyard and winemaking parameters affect the levels of thiols in wines, the work also demonstrates the role the matrix plays in the sensory perception of these impact compounds.
The result indicate that, depending on the presence of other volatile and non-volatile substances and on the level of thiols, the perception of aroma is affected by thiol x thiol, thiol x aroma compounds (for example terpenes and esters), and thiol x non-volatile matrix interaction effects.
These effects influence the nature and the intensity of attributes, with demonstrable synergistic and masking phenomena in a series of increasing complexity matrices from model wine to dearomatised neutral Chenin Blanc to a variety of commercial wines.