Sensory profile of rooibos originating from the Western and Northern Cape governed by production year and development of rooibos aroma wheel

- A large sample set of fermented rooibos samples were sourced from 2011 to 2013.
- Samples originated from the Western Cape and Northern Cape, South Africa.
- Rooibos aroma profile was affected by production year, but not area.
- Primary and secondary aroma profiles were identified.
- Rooibos aroma wheel incorporates attribute intensity and occurrence.

Aspalathus linearis is cultivated in the Western Cape and Northern Cape provinces of South Africa for the production of rooibos, a herbal tea with a global footprint. A total of 208 samples, spanning the two production areas, three production years and three quality grades, were collected to delineate the effect of production area and year on rooibos sensory properties, as well as to ensure large variation, required for revision of the rooibos sensory wheel. The samples were analysed using descriptive sensory analysis to provide comprehensive profiling of aroma, flavour, taste and mouthfeel attributes. The primary aroma characteristic profile of rooibos, previously described as “rooibos-woody”, “fynbos-floral” and “honey” was confirmed. Other aroma attributes that were perceived frequently and at high intensity in the sample set were “fruity-sweet”, “caramel” and “apricot”. Although not occurring as commonly as those of the primary aroma profile of rooibos, these attributes, manifested in samples from both production areas, forming a secondary aroma profile. In the present study the “hay/dried grass” aroma note appeared in 99% of the rooibos samples at low intensities and could therefore be considered to be part of the “characteristic” aroma profile of rooibos. No clear differences between production areas were evident, but production years could be distinguished based on differences in perceived aroma attribute intensities. The aroma wheel is more user-friendly as it will provide users, at a glance, with the relative importance of attributes (as determined by intensity and occurrence frequency). This is achieved by varying slice width according to the relative mean attribute intensity and the use of accompanying bar graphs indicating relative occurrence frequency of attributes. This quality control and “communication” tool can be used by industry to aid in the grading and marketing of rooibos tea.