Supercritical fluid extraction of torch ginger: Encapsulation, metabolite profiling, and antioxidant activity

Objectives: The objective of this study was first to perform the supercritical fluid extraction (SFE) and encapsulationof torch ginger (Etlingera elatior) inflorescences into a functional powder. Second objective was to evaluate the powder's characteristics, metabolite profiles, and antioxidant activity. Methods: Torch ginger inflorescences were extracted via SFE technique, and the obtained extract was encapsulated by a spray-drying process with maltodextrin as an encapsulating agent. Subsequently, the powder was evaluated for its physical characteristics, determination of metabolite profiles by using a Fourier Transform Infrared Spectrophotometer (FTIR) and Gas Chromatography-Mass Spectrometry (GC–MS), and antioxidant activity. Results: Spray drying encapsulation process managed to yield around 59.8% of torch ginger extract powder (TGEP) by using 10% of extract, which the obtained yield was twice higher than in another study. TGEP showed inconsistent agglomeration behaviour in particle size examination with distinct sizes concentrating at 2.2 μm and 17.4 μm, respectively. Brunauer-Emmett-Teller (BET) analysis of TGEP unveiled a considerably high surface area (1.13 m²/g), pore volume (0.218 cm³/g), and pore size (384.6 nm). The metabolites profile of TGEP was studied and characterized using two spectroscopic analyses. Analysis by the FTIR showed the presence of O–H, C–H, C = C, C = O, CO-O-CO, C-N, and C-O functional groups in the sample. Subsequently, the result of the GC–MS characterization revealed about 59 metabolites that predominantly fatty acids (30.5%), terpenes and derivatives (20.3%), fatty acid esters (16.9%), and alcohols (8.47%) were present in TGEP. The powder also demonstrated a high antioxidant activity based on the evaluation of its total phenolic content (23.3 ± 0.662 mg GAE/g TGEP), EC₅₀ as determined from 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity assay (1.31 ± 0.002 mg/mL), and ferric reducing antioxidant power (2919.5 ± 19.9 μM TE/g TGEP), which were better than previous studies. Conclusion: Therefore, this study unveiled TGEP as a functional powder with a high content of bioactive compounds with excellent bioactivity.