Development and validation of prediction models and rapid sensory methodologies to understand intrinsic bitterness of Cyclopia genistoides

[摘要] ENGLISH ABSTRACT: Cyclopia species, endemic to South Africa, is used for the production of honeybush tea. This herbal tea has grown from a product consumed only locally to one currently marketed worldwide. Cyclopia species ishigh in polyphenols, well-known for its health related properties, but these compounds could contribute tobitterness, which may elicit negative consumer response. One of the species, C. genistoides, is high inpolyphenols but also associated with bitterness, contrary to the characteristic sweet taste and honey-like flavourassociated with honeybush.The polyphenolic content of four Cyclopia species were quantified with high-performance liquidchromatography diode-array detection while descriptive sensory analysis (DSA) was used to determine thetaste intensities of these samples. The link between phenolic content and bitterness was investigated. Basedin the phenolic content of C. genistoides and C. longifolia, partial least squares (PLS) regression analysisidentified four compounds, mangiferin, isomangiferin, iriflophenone-3-C-glucoside-4-O-glucoside andiriflophenone-3-C-glucoside, as candidate predictors of bitterness. This model will find application asscreening tool in cultivar development research programs.Production of honeybush lags behind demand, forcing the industry to use blends of Cyclopia species,including C. genistoides, to supply in the increased demand. The distinct differences in the sensory profilesassociated with different Cyclopia species require that special care is given to blending to ensure a consistent,high quality product. DSA was used to evaluate the effect of blending of C. genistoides with other Cyclopiaspecies on bitterness. Blending of C. genistoides with C. subternata, C. intermedia or C. maculata in a ratioof 2:3 were effective in reducing bitterness to below perceptible levels. The sensory profile of C. genistoides-C. subternata blends were further quantified using DSA and was described as 'fynbos floral, 'apricot,'woody, 'fruity sweet and 'fynbos sweet aroma and a sweet taste. Based on these results, inclusion of C.genistoides at 40% when blending different Cyclopia species, is recommended. Blending at this standardisedratio will result in a well-rounded product with bitterness below perceptible levels.The herbal tea industry expressed the need for time- and cost-effective methods for sensory screeningof infusions to improve quality and product consistency. The validity of three rapid profiling methods {sorting,projective mapping and polarised sensory positioning (PSP)} for the sensory characterisation of honeybushinfusions were investigated using a trained panel. The efficacy of partial (aroma or palate attributes) or global(all attributes) evaluation was compared within each rapid method. Product configurations similar to that ofDSA demonstrated the validity of all three methods for broad sensory profiling of Cyclopia species. Sortingon palate attributes resulted in additional differentiation between samples with only subtle differences. Sortingdemonstrated to be the most effective method for the broad sensory profiling of honeybush infusions and couldfind application in the honeybush industry as screening tool. PSP on the other hand could find application inquality control programs where poles that represent specific quality attributes, should be included.Implementation of valid, scientific methods, such as sorting and PSP, will aid the honeybush industry in theireffort to supply a product with consistent quality and high consumer appeal.

[发布机构] Stellenbosch University