Characterization of Chenin Blanc wines produced by natural fermentation and skin contact : focus on application of rapid sensory profiling methods

[摘要] ENGLISH ABSTRACT: Producers of South African (SA) dry and semi-dry Chenin blanc table wines are currentlyexperimenting with winemaking techniques to modulate the flavours of the predominantly fruitystyles of this genre. An important stage during wine style development is sensory profilingpaired with consumer acceptance testing, before wine is produced on industrial scale. Withthose aforementioned goals in mind, this study was conducted in partnership with twocommercial SA wine cellars.The main focus of the study was an investigation into the treatment effects of two winemakingtechniques, respectively grape skin contact and natural fermentation, on the sensory profiles ofexperimentally produced Chenin blanc wines. Results obtained with descriptive sensoryanalysis (DA) of the wines were compared to those obtained by two rapid sensory profilingmethods, namely projective mapping (PM) and frequency of attribute citation (FC). A consumerpreference study was also done on the wines. In order to understand the treatment effectsbetter, the dominant non-Saccharomyces yeasts that were present during the naturalfermentations were identified using polymerase chain reaction (PCR), while the major volatilechemical compounds were identified with chromatography and mass spectrometry.The sensory and chemical profiles of the naturally fermented wines were significantly differentfrom those of the inoculated wines. PCR analysis identified some of the yeasts present duringalcoholic fermentation. In comparison to the inoculated fermented wines, the naturallyfermented wines were generally perceived to have more intense and riper tropical fruity aromas,with enhanced sweetness and reduced intensities of sourness, bitterness and astringency.The wines fermented on the skins (FoS) had lower ester and volatile thiol concentrations thanthe control wines (with no skin contact) and limited skin contact wines. Sensory attributes linkedto the FoS wines included aromas of dried fruit, dried grass and a vegetative character, with anincreased sour and bitter taste and astringent mouthfeel. In contrast, the wines that wereproduced with limited skin contact (12 hours) retained their tropical fruity aromas better than theFoS wines. Limited skin contact seemed to have had a less harsh effect on the taste andmouthfeel than the FoS wines. A consumer study was done to establish a Generation Yconsumer group's (18-35 years) preference for the different treated wines. Overall, the naturallyfermented wines, which were described as having a strong tropical fruit character, werepreferred. The FoS wines were generally disliked by the consumers.Results obtained from the three sensory analysis methods, respectively DA, PM and FC, weresimilar, thereby confirming the suitability of the rapid methods PM and FC, to extract qualitativeinformation from the sensory profiling of white wine.The results of this study made a significant contribution towards validation of rapid sensorymethods for wine evaluation, which are particularly valuable in the context of sustainability andtechnology transfer to research and industry alike. The knowledge gained on the chemicalprofiles of SA Chenin blanc is novel and this is one of the first reports on the volatile thiolcontent of SA Chenin blanc wine.

[发布机构] Stellenbosch University