Characterisation of the sensory profile of Cyclopia intermedia and optimisation of fermentation parameters for improved product quality

["Honeybush tea -- Sensory evaluation", "Cyclopia intermedia -- Sensory evaluation", "Fermentation", "Dissertations -- Food science", "Theses -- Food science", "UCTD"]

Bergh, Alexandra Jane ; Joubert, Elizabeth

Stellenbosch University

Others  :  https://scholar.sun.ac.za:443/bitstream/10019.1/95908/3/bergh_characterisation_2014.pdf

瑞士|英语

来源: Stellenbosch University

【 摘 要 】

ENGLISH ABSTRACT: In light of the limited and inconsistent supply of good quality honeybush tea, a species-specific sensory profile and the physicochemical characteristics of Cyclopia intermedia (honeybush) tea were determined to ultimately establish the optimum fermentation parameters for this herbal tea on laboratory-scale and to validate these findings on commercial-scale. The characteristic sensory profile of C. intermedia can be described as sweet tasting and slightly astringent with a combination of 'fynbos-floral, 'fynbos-sweet, 'fruity (specifically 'apricot jam, 'cooked apple, 'raisin and 'lemon/lemon grass), 'woody, 'caramel/ vanilla and 'honey-like aromas. The flavour can be described as distinctly 'fynbos-floral, 'fynbos-sweet and 'woody, including hints of 'lemon/lemon grass and 'hay/dried grass. The results of the sensory study were used to create a C. intermedia sensory wheel and lexicon, and an elementary grading system that categorised samples into 'good, 'average and 'poor sensory quality was proposed. Physicochemical parameters, i.e. soluble solids (SS) content, absorbance as a measure of colour, and turbidity, were evaluated as possible rapid predictors of sensory quality. High SS content, absorbance and turbidity correlated strongly with 'poor sensory quality. A linear relationship existed between the physicochemical parameters.The effect of fermentation temperature (70, 80 and 90°C) and time (12, 16, 24, 36, 48 and 60 h) on the sensory and physicochemical characteristics of C. intermedia was determined on laboratory-scale. Increasing fermentation time increased the intensity of positive sensory attributes, while decreasing the intensity of negative sensory attributes. The SS content, colour and turbidity of infusions decreased with increasing fermentation time, while the SS content and turbidity of infusions increased with increasing fermentation temperature. Fermentation at 90°C for 36 h on laboratory-scale produced C. intermedia with the best sensory properties, while preserving the SS content and colour of infusions. Fermentation at 70°C and 80°C required longer fermentation times for development of positive sensory attributes. Fermentation at 90°C was subsequently validated on commercial-scale. Laboratory-scale fermentation of the same batches of plant material was also carried out concurrently to allow direct comparison of the scale of fermentation on tea quality. Commercial-scale fermentation, despite increased variability as a result of increased batch volumes and heating difficulties, produced C. intermedia of 'good sensory quality after 24 and 36 h of fermentation. Increasing fermentation time had little effect on the SS content and colour of infusions of tea produced on commercial-scale, but turbidity increased significantly after 36 h. Thus, to produce C. intermedia with consistently good quality on commercial-scale, fermentation at 90°C for 24 to 36 h is recommended. Increasing fermentation time past 48 h should be avoided to prevent turbidity and the development of sensory attributes characteristic of over-fermented tea. However, due to the large variability of commercial-scale honeybush tea production, it is recommended that each batch be monitored between 24 and 36 h to determine when optimum fermentation has been obtained.