Effect of genotype and harvest season on quality characteristics of Cyclopia subternata: Phenolic content and sensory profile

Abstract

Cultivation of selected Cyclopia species, including C. subternata, is the only viable option to ensure that the current growth trajectory of the honeybush industry is maintained. Gaps in honeybush production knowledge still exist, including the optimum harvest season for production of good quality honeybush, as defined by the phenolic content of the leaves, which is related to bioactivity of extracts, as well as the sensory profile of the herbal tea. The aim of this study was to determine the optimal harvest season for achieving the maximum accumulation of phenolic compounds in the leaves of six genotypes (SGD2, SGD3, SGD6, STB1, SHL2, SKB3) under evaluation by the honeybush breeding programme of the Agricultural Research Council. The major phenolic compounds were quantified by HPLC-DAD. Plants were harvested in summer, autumn, winter and spring. The plant material was also processed to determine whether genotype and harvest season affect the sensory profile of honeybush tea as determined by descriptive sensory analysis. Both genotype and harvest season affected the phenolic content of the leaves and the sensory profile of the herbal tea. Overall, the summer harvest delivered the better product. SGD3 emerged as the genotype with the highest total phenolic content of the leaves (p < 0.05), predominantly due to higher accumulation of the benzophenone, 3-β-D-glucopyranosyl-4-O-β-D-glucopyranosyliriflophenone, and xanthones, mangiferin and isomangiferin. However, herbal tea from SGD3 also had a higher intensity of the negative aroma attribute, ‘hay/dried grass’, although not significantly different from SGD2, SHL2 and STB1 (p ≥ 0.05). Considering the positive aroma attributes, STB1 had either the lowest or lower intensities (p < 0.05) of ‘fynbos-floral’, ‘apricot jam’, ‘fruity-sweet’ and ‘fynbos-sweet’ than the other genotypes. By identifying summer as optimum harvest time, a foundation is laid for screening of more genotypes to expand the genetic pool and to determine the effect of cultivation practices on quality.