Novel Electromagnetic Heat Hydrodistillation for Extraction of Essential Oil from Tangerine Peel

Abstract

A novel electromagnetic heat method is presented for green extraction of natural compounds from peel residue. In the processing cavity obtained through 3D printing, a core made of amorphous alloy was applied to strengthen the magnetic flux. During the process, an induced electric field was produced in the extract medium owing to an oscillating magnetic field at 50 kHz rather than a pair of electrodes; thus, electrochemical reactions could be avoided. A thermal effect and temperature rise were observed under the field, and essential oil was obtained via this electromagnetic heat hydrodistillation. In addition, the numerical relationships between magnetic field, induced electric field (IEF), induced current density, and temperature profile were elaborated; they were positively correlated with the extraction yield of essential oils. It was found that the waveforms of the magnetic field, induced electric field, and excitation voltage were not consistent. Using a higher magnetic field resulted in high current densities and terminal temperatures in the extracts, as well as higher essential oil yields. When the magnetic field strength was 1.39 T and the extraction time was 60 min, the maximum yield of essential oil reached 1.88%. Meanwhile, conventional hydrodistillation and ohmic heating hydrodistillation were conducted for the comparison; all treatments had no significant impact on the densities. In addition, the essential oil extracted by electromagnetic heat had the lowest acid value and highest saponification value. The proportion of monoterpenoids and oxygen-containing compounds of essential oil extracted by this proposed method was higher than the other two methods. In the end, the development of this electromagnetic heat originating from magnetic energy has the potential to recover high-value compounds from biomass waste.

Keywords: electromagnetic heat; essential oil extraction; oscillating magnetic field; physicochemical properties.

Figure 1

Principle of novel electromagnetic heat hydrodistillation on extract solution. (a) Extracts in a container subjected to the magnetic field; (b) winding coil on a magnetic core excited by the current; (c) extracts in a spiral winding subjected to the magnetic field.

Figure 2

Electromagnetic heat hydrodistillation apparatus for the essential oil extraction. 1. Power source, 2. Magnetic core, 3. Primary winding, 4. Secondary winding of pipeline (3D printing material: PC-ISO, Stratasys, Eden Prairie, MN, USA), 5. Sample bottle, 6. Pump, 7. Control panel, 8. Cooling system, 9. Oscilloscope, 10. Collecting bottle, 11. Magnetic stirrer, 12. Essential oil receiver, 13. Condenser tube.

Figure 3

Waveforms sampling. (a) Excitation voltage and induced voltage (or IEF loaded on extracts solution); (b) the produced oscillating magnetic field.

Figure 4

Influence of the magnetic field on the winding of extract solution at a solid–liquid ratio of 1:20. (a) Induced current density within the extract solution; (b) terminal temperature for retention time 60 min; (c) energy efficiency of the process. The different letters indicate significant differences at a 0.05 level.

Figure 5

Influence of the proposed electromagnetic heat on essential oil yield from tangerine peel. (a) Magnetic field strength; (b) solid–liquid ratio; (c) extraction time. The different letters indicate significant differences at a 0.05 level.

Figure 6

Scanning electron microscope (5000×) images of tangerine peel after different treatments. (a) Untreated; (b) conventional hydrodistillation; (c) ohmic heating hydrodistillation; (d) electromagnetic heat hydrodistillation.