Optimisation of the Extraction Process and Quality Attributes of a Roselle (Hibiscus sabdariffa L.) Leaf Tisane Beverage

This study investigated the optimisation of roselle (Hibiscus sabdariffa L.) leaf tisane formulation using response surface methodology (RSM), targeting total phenolic content (TPC), ferric reducing antioxidant power (FRAP), and DPPH radical scavenging activity as quality indicators. A face-centred central composite design was employed to evaluate dose effects (0.5–2.5 g) and infusion time (5–15 min). Multi-response optimisation using the desirability function identified 1.81 g dose and 5 min infusion as the optimum condition, yielding predicted values of 24.46 mg GAE/100 mL (TPC), 61.07 µmol Fe2+/100 mL (FRAP), and 80.47% (DPPH), with a composite desirability score of 0.64. Validation experiments confirmed strong predictive accuracy, with deviations of 0.80% (FRAP) and 3.92% (DPPH), and a modest deviation of 13.2% (TPC), acceptable within complex food matrices. The findings demonstrate that short infusion times are sufficient to extract key bioactives, ensuring consumer convenience and energy efficiency, while valorising roselle leaves as an underutilised by-product into a sustainable functional beverage. Future studies should address sensory acceptance, stability, and bioavailability to support industrial applications further.