Alain Samson

Sensory representation of typicality of Cabernet franc wines related to phenolic composition: Impact of ripening stage and maceration time

Phenolics are responsible for important sensory properties of red wines, including colour, astringency, and possibly bitterness. From a technical viewpoint, the harvest date and the maceration duration are critical decisions for producing red wine with a distinctive style. But little is known about the evolution of phenolics and of their extractability during ripening to predict the composition of the wine and related sensory properties. The aim of this study was to understand the relationship between the sensory profile of the wines and (i) the ripening stage of the berries (harvest date) and (ii) the extraction time (maceration duration). Phenolic acids, flavonols, anthocyanins and proanthocyanidins of Vitis Vinifera var. Cabernet franc were measured in grapes and in wines from two stages of maturity and with two maceration durations. Phenolic composition was analysed by high performance liquid chromatography, after fractionation and thiolysis for proanthocyanidins. The distinctive style of wines was investigated by descriptive analysis (trained panel), Just About Right profiles and typicality assessment (wine expert panel). Relationships between phenolics and sensory attributes were established by multidimensional analysis, and phenolics were classified according to sensory data by ANOVA and PLS regressions. Astringency, bitterness, colour intensity and alcohol significantly increased with ripening and astringency and colour intensity increased with maceration time. Grape anthocyanins increased and thiolysis yield significantly decreased with ripening. In wine, proanthocyanidins increased, and mean degree of polymerisation and thiolysis yield decreased with longer extraction time. The high impact of harvest date on the sensory profiles could be due to changes in anthocyanin and sugar contents, but also to an evolution of proanthocyanidins. Moreover, proanthocyanidin composition was affected by maceration time as suggested by the decrease of thiolysis yield. Our results suggest that the wine sensory quality established by the expert panel, is linked as expected to grape quality at harvest, reflected by sugar and anthocyanin contents, but also by thiolysis yield, which requires elucidation.

Models based on ultraviolet spectroscopy, polyphenols, oligosaccharides and polysaccharides for prediction of wine astringency

Astringency elicited by tannins is usually assessed by tasting. Alternative methods involving tannin precipitation have been proposed, but they remain time-consuming. Our goal was to propose a faster method and investigate the links between wine composition and astringency. Red wines covering a wide range of astringency intensities, assessed by sensory analysis, were selected. Prediction models based on multiple linear regression (MLR) were built using UV spectrophotometry (190-400 nm) and chemical analysis (enological analysis, polyphenols, oligosaccharides and polysaccharides). Astringency intensity was strongly correlated (R(2) = 0.825) with tannin precipitation by bovine serum albumin (BSA). Wine absorbances at 230 nm (A230) proved more suitable for astringency prediction (R(2) = 0.705) than A280 (R(2) = 0.56) or tannin concentration estimated by phloroglucinolysis (R(2) = 0.59). Three variable models built with A230, oligosaccharides and polysaccharides presented high R(2) and low errors of cross-validation. These models confirmed that polysaccharides decrease astringency perception and indicated a positive relationship between oligosaccharides and astringency.

Use of Production Practices and Sensory Attributes to Characterize Loire Valley Red Wines

Quality wines are typically the product of soil, climate, and wine production practices. Sensory attributes are increasingly used to distinguish among protected designation of origin (PDO) wines. Since 2010, the International Organization of Vine and Wine has taken all such parameters into account in an official definition of terroir. However, links between production practices and sensory attributes in geographically circumscribed PDO areas had not been investigated until now. Production practices and sensory attributes of distinct PDO wines within the same area were assessed. The production practices of producers of 33 commercial PDO wines from the Loire Valley, France, were surveyed, including vineyard training systems, viticulture, harvest timing, winemaking, and aging practices. Descriptive sensory analysis was conducted to characterize the significant sensory attributes of these same wines. PDO wines were separated from one another by classical statistical analyses. About 25% of the analyzed production practices and less than 50% of the analyzed sensory attributes could differentiate PDO wines produced in the same area: percentage of Cabernet franc, time of leaf removal, harvest date, yield, duration of fermentation, duration of aging and use of oak, color intensity, viscosity, cloudiness, blackcurrant, prune, spicy, moldy, animal, bitterness, and astringency. Relationships between some production practices and sensory attributes were identified. Results demonstrate that, under similar climatic conditions and soil characteristics, production practices and sensory attributes can distinguish PDO wines in well-defined geographic areas.

Effect of storage in glass and polyethylene terephthalate bottles on the sensory characteristics of rosé wine

Background and Aims We studied the ageing of rose wine in polyethylene terephthalate (PET) bottles compared to that in the reference glass bottle, as the PET bottle needs less energy for manufacture, transport and recycling, which is of benefit for minimising environmental concerns. Our study focused on the evolution of the sensory characteristics of rose wine. Methods and Results Sensory characteristics were monitored over a period that corresponded to the duration of marketing of this type of wine. Several types of PET bottle – recycled, not recycled, with or without oxygen scavengers – were compared with the glass bottle. The wines were subjected to sensory analysis using the methodology of conventional descriptive profile by an expert panel. The impact of PET bottles on the colour and sensory characteristics of rose wine was significant, which was due mainly to oxygen transfer through the PET bottle. The impact was much less for the taste characteristics. Conclusions Packaging rose wine in PET bottles has a significant impact on the evolution of rose wine. Significance of the Study These results can guide professionals in the choice of packaging according to the wine.