Effect of the microwave and thermosonic vacuum concentration methods on quality parameters of hibiscus (hibiscus sabdariffa L.) extract and mathematical modeling of concentration

Abstract This study investigates the modeling of the concentration of hibiscus extracts and the effect of the concentration process on some quality properties of hibiscus extracts. Absolute pressure was applied as 250 mbar in all concentration processes. Thermal vacuum concentration process was applied at 75 °C and 80 °C, thermosonic vacuum concentration process was applied at 75 °C and 0.02 W/mL AED, and microwave vacuum concentration treatment was applied at 180 and 300 W. The shortest processing time was achieved with the microwave vacuum concentration process at 300 W. Among the 13 models used, Midilli was the most successful model (R 2 ≥ 0.9951, χ2 ≤ 1.0185 and RMSE ≤ 1.0092)) in describing the concentration data. No significant change was determined in the physicochemical properties of the concentrated samples. However, a significant increase was determined in the turbidity values of the concentrated hibiscus samples, while a significant decrease was noted in the anthocyanin content and composition and antioxidant activity values of the concentrated samples compared to the initial sample.