Ohmic-assisted hydrodistillation of citronella oil from Taiwanese citronella grass: Impacts on the essential oil and extraction medium

Abstract

Abstract Citronella oil was extracted from Cymbopogon nardus by ohmic-assisted hydrodistillation (OAHD) and hydrodistillation (HD) and its specifications were studied by DPPH assay and chromatography-mass spectrometry. The changes in extraction media were also studied by inductively coupled plasma-mass spectrometry. HD and OAHD yielded the same amount of essential oil (1.5% w/w), with similar physical properties. Conversely, OAHD yielded a higher value essential oil, considering the stronger antioxidant activity (IC50 of 326 vs. 428 μg/mL) and the enhanced concentration of valuable compounds such as citronellal (77.5 ± 0.2 vs. 74.8 ± 0.2) and d -limonene (3.3 ± 0.2 vs. 1.8 ± 0.0). OAHD also saved 46% and 79% of the process time and energy, respectively. However, electrode corrosion was observed in OAHD and metal ions were transferred from titanium electrodes into the extraction medium (Ti concentration: 0.05 mg/L). Precautions to minimize electrode corrosion should be considered for industrial adaptation of OAHD. Industrial relevance Ohmic-assisted hydrodistillation is a promising extraction technique to enhance the product quality and to reduce the production time and consumed energy. This innovative technique has the potential of increasing the production capacity and decreasing the production cost for essential oil and distillatory industries. However, this study revealed the occurrence of electrochemical reactions between electrodes and extraction media which resulted in metal ion migration and residue pollution. Therefore, selecting appropriate materials as the OAHD electrodes, optimizing the process parameters and careful handling of the production waste should be considered for industrial application of this emerging method.