Identification of broad-based sensory attributes driving consumer preference of ready-to-drink rooibos iced tea with increased aspalathin content

Abstract

Traditional rooibos iced teas prepared using fermented rooibos extract contain a low concentration of the unique antioxidant, aspalathin, which also has anti-diabetic properties. In order to increase the aspalathin content an array of rooibos iced tea formulations containing aspalathin-enriched green rooibos extract or the same extract solubilised in nanomicelles in the presence of ascorbic acid (solubilisate), as well as a mixture of the solubilisate and fermented extract, were formulated with or without lemon flavour. Since sensory attributes are important from a consumer viewpoint, the broad-based sensory attributes of these formulations were compared with those of traditional fermented rooibos iced tea. The iced tea formulations containing green rooibos extract exhibited a “plant-like” character, which was reduced with the addition of a commercial lemon flavour. The formulations containing the solubilisate had a prominent “hay-like” flavour, which was reduced by the addition of both lemon flavour and fermented rooibos extract. The formulations containing fermented rooibos extract exhibited a prominent “rooibos-woody” flavour characteristic of fermented rooibos tea. The perceived intensity of this characteristic attribute decreased with addition of commercial lemon flavour and solubilisate. All the iced teas exhibited a measure of astringency, but the astringency of iced teas containing fermented extract was the greatest and was reduced by addition of lemon flavour. In order to gauge consumer acceptance, the four lemon flavoured variants of rooibos iced tea were evaluated by a consumer panel. Consumers preferred the iced teas with fermented rooibos extract and disliked those with green rooibos extract. Preference mapping showed that the presence of the “rooibos-woody” flavour and the absence of a “plant-like” flavour most likely drive the preference of rooibos iced teas amongst South African consumers. The presence of a slight “hay-like” character did not reduce the preference of rooibos iced teas. Despite the functional benefits associated with a higher aspalathin content of green rooibos iced tea compared to the traditional fermented rooibos iced tea, consumers disliked the product, because of its overt “plant-like” note. However, a green rooibos extract solubilised in nanomicelles in combination with the fermented extract can be used to produce an iced tea with enhanced aspalathin content that is still acceptable to consumers from a taste point of view.