Impact of harvest season on sensory and phenolic profiles of selected clones of Cyclopia subternata (honeybush)

Title : Impact of harvest season on sensory and phenolic profiles of selected clones of Cyclopia subternata (honeybush)

Abstract:

Cyclopia subternata (honeybush) is a commercially important South African fynbos plant used as a herbal tea. Some genotypes produce a bitter-tasting tea, contrary to the “sweet, honey-like” beverage, typically associated by consumers with honeybush tea. Furthermore, this species is a rich source of bioactive xanthones, benzophenones and flavanones. The objective of this study was to determine the impact of harvest season on the sensory and phenolic profiles of selected clones of C. subternata. Sensory and phenolic profiles are second tier criteria for selection of honeybush plant material for breeding purposes. Six clones were selected, based on biomass yield and the rooting and survival of cuttings. The plant material was processed, including “fermented”, and a hot water infusion of the “tea bag fraction” subjected to sensory analysis entailing descriptive sensory analysis. Standardised protocols were followed for processing and sensory analysis. The data were analysed using univariate and multivariate statistical procedures. The phenolic content of the leaves (unprocessed) was determined by HPLC-DAD and analysed using the univariate ANOVA. The results showed that harvesting season significantly affected the phenolic content of honeybush. Harvesting in summer and winter resulted in infusions with the highest intensities of positive aroma attributes; however, no clear trend for harvest season could be established for taste modalities. The highest phenolic content was recorded in summer and autumn, whereas the opposite was evident in winter. Significant differences in terms of sensory attributes and phenolic content were observed between clones, with some clones less affected by harvesting season. The differences in harvest season and clones may guide selection of clones for breeding programmes aiming at improving herbal tea quality and/ or nutraceutical value.

Biography:

Gugu S. Mabizela was born in Newcastle (Madadeni), a small town in KwaZulu-Natal where she matriculated in 2006. After completing her undergraduate studies at the Tshwane University of Technology (TUT), she joined the Agricultural Research Council (ARC) as a PDP student in 2012. She received her M.Tech in Horticulture from TUT in May 2015 and is currently registered as a PhD student in the Horticulture Department of the Science Faculty at TUT. The title of her PhD study is “Metabolic profiling of Cyclopia subternata and C. genistoides in response to drought stress and seasonal variation” and aims to complete it in 2019. During her Master’s studies, Ms Mabizela published an article in the South African Journal of Botany on the effect of growth media, plant growth regulators and clone on rooting potential of Cyclopia subternata stem cuttings at different planting dates. Ms Mabizela received a fellowship to attend and present at the International Conference on Women in Science, Technology, Engineering and Mathematics (STEM) in Sandton during November 2015 and presented at eight other conferences in South Africa. In 2016 she gave a poster presentation at the 20th Eucarpia General Congress at ETH in Zurich. In 2018 Ms Gugu Mabizela received full sponsorships from DowDuPont to cover all her expenses to attend the SA Plant Breeders Association Conference. She also had the privilege to present in the DowDuPont Plant Sciences Symposium, together with Dr Geoff Graham (DuPont Pioneer Research Vice President for Global Plant Breeding, DuPont Pioneer, and Des Moines, Iowa, USA) and three other sponsored students. At the end of her studies, Ms Mabizela would like to make a significant impact in the agriculture research community by applying her acquired skills and experience in this field. Ms Mabizela is currently residing in Stellenbosch, Western Cape where she is undertaking her research with the ARC Infruitec-Nietvoorbij.