Doctoral Degrees (Institute for Wine Biotechnology)

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Browsing Doctoral Degrees (Institute for Wine Biotechnology) by browse.metadata.advisor "Næs, T."

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    Rapid sensory profiling methods for wine : workflow optimisation for research and industry applications
    (Stellenbosch : Stellenbosch University, 2019-04) Brand, Jeanne; Nieuwoudt, Helene; Vivier, Melane A.; Valentin, Dominique; Næs, T.; Stellenbosch University. Faculty of Agrisciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology.
    ENGLISH ABSTRACT: Descriptive sensory analysis techniques are widely used and trusted methodologies. Due to time and cost constraints, the demand for cost-effective methods for profiling is growing rapidly in food and beverage industries including the wine industry. A number of rapid methods have been tested and validated for various food products. However, further work is needed to identify and address limitations of specific rapid methods, especially reference-based methods, when evaluating complex matrices such as wine. The majority of studies employed novice consumers or trained consumers as judges. The wine industry has an advantage over most food industries with: (1) product experts who can serve as judges and (2) having an extensive lexicon in the form of aroma wheels available that can be used as check-all-that-apply (CATA) questions. The objective of this study was to identify cost-effective, rapid sensory methods that can be used for wine profiling by researchers and the wine industry alike. Furthermore, the study aimed to optimise the identified methods and to propose workflows that include sensory methods and statistical procedures suited for wine sensory analysis applications. Four rapid methods were compared to descriptive analysis (DA). The methods tested were CATA, rate-all-that-apply (RATA), Napping, and sorting. Results obtained for the rapid sensory method and DA were similar. It can therefore be concluded that rapid methods are suitable for the sensory evaluation of wine. Industry professionals can therefore be used as sensory judges, and can use a pre-determined lists of attributes as verbalisation tools. CATA and sorting provided the highest quality profiles with the best discrimination between products. Sorting highlights similarities and differences whereas CATA provides more detailed descriptions. In addition, these two methods were found to be easier than rate-all-that-apply (RATA) and Napping to use. Pivot profile (PP), a reference-based method, was validated against a CATA variant, namely frequency of attribute citation (FC). It was concluded that PP should be used with caution because the choice of pivot on the sensory space could have an influence. This method could, however, be useful when direct comparisons between samples are required, such as benchmarking. In addition to sensory method development, a number of statistical procedures were also proposed to assist with the interpretation of rapid method data. A workflow to calculate drivers of quality and a strategy to calculate confidence ellipses for PP data were developed. This study highlights the importance of selecting a fit-for-purpose method. The objective of the experiment being conducted, along with practical restrictions should be taken into account when deciding which method to use.