Optimisation of α-pinene from Eucalyptus deglupta through hybrid drying of ultrasound assisted osmotic dehydration (UOAD) and hot-air drying

Eucalyptus Deglupta is one of the promising medicinal plants from Mytracea family consisting of bioactive compounds that are to be used in medications. α-pinene presents Eucalyptus Deglupta is a medicinal bioactive compound with health benefits. This research aims to optimise the hybrid drying conditions in order to increase the yield of α-pinene, total phenolic content and antioxidant activity of Eucalyptus Deglupta. The optimization was conducted via Response Surface Methodology (RMS) with design central composite design (CCD) design to study the interactions between the parameters to attain a maximum yield of α-pinene. Four parameters are optimized, namely concentration of sucrose, temperature, duration of drying and intensity of ultrasound to give a series of 27 combinations of the pre-drying conditions. Complete drying was followed by hot- air drying performed at 60℃. The optimal pre-drying condition was identified. The concentration of sucrose , temperature , duration of drying and intensity of ultrasound were 50%, 37.59℃, 100 minutes and 330 W, respectively with a yield of antioxidant at 56.12%, total phenolic content (TPC) at 0.483 mgGAE/0.1 g of dried leaf and α-pinene at 5.737 ppm. The best-fitted mathematical drying kinetic model was Henderson Pabis model with the highest coefficient of determination value of 0.9989 and the lowest root mean squared value of 0.0475.