Optimization of Ultrasound-Assisted Cold-Brew Method for Developing Roselle (Hibiscus sabdariffa L.)-Based Tisane with High Antioxidant Activity

Edible flowers, including roselle, contain a varied composition of phenolic compounds that may inhibit the oxidative stress mechanism. Roselle-based tisane with appealing sensory properties is commonly consumed worldwide. However, conventional hot-brew method ruin stability thermolabile during preparation. Hence, this study aimed to develop new alternative brewing linked cold-brew method, which involves lower temperature and applying ultrasound maximize extraction avoid degradation The factors, particle size (10, 20, 30 mesh), (4, 15, 26 °C), time min), amplitude (20, 60, 100% maximum amplitude) have been optimized simultaneously using Box–Behnken design in conjunction response surface methodology. Seven major were identified by HPLC-DAD classified into hydroxycinnamic acid derivatives (HCA) flavonoids. optimum condition reach highest level studied was set brew roselle ± 3.25 mesh at 1.32 °C for 18 2.00 min 78 5.64% amplitude. This successfully extracted almost all HCA flavonoid first cycle less than 10% CV provided higher antioxidant activity terms DPPH (IC50 9.77 0.01 µg mL−1), ABTS 8.05 0.02 FRAP 10.34 0.03 mL−1) prepared method. Additionally, resulting product stable up five days storage.