An experimental system for extraction of pectin from orange peel waste based on the o-core transformer structure

• A system based on the o-core transformer structure was designed and built.
• Extraction efficiency was improved by the use of an induced electric field.
• The pectin yield was enhanced by the increase of excitation voltage.
• Electric field frequency at 20–200 kHz had a negative impact on pectin yield.
• The adoption of magneto-electric mutual conversion avoided the use of electrodes.

An experimental system based on the o-core transformer structure was established and used to extract pectin from orange peel waste. Unlike other electric-field-assisted techniques, it avoids the use of powered electrodes. The acidic solvent acts as the secondary coil connected to a purpose-made glass chamber which forms a closed loop. Then the induced electric field in the system appears to be under the influence of alternating magnetic flux based on Faraday's law of induction. We found that an increase in the excitation voltage causes enhancement of the pectin yield. Increasing frequency from 20 to 200 kHz had a negative impact on pectin yield partially due to the increased impedance of the primary coil. The ionic conduction was enhanced at the same excitation voltage since there are more free ions in the mixture at lower pH. This means that a lower impedance in the mixture is conducive to extraction. This multidisciplinary technique combines the transformer concept with the electric-field-assisted process, thus providing a reference for the application into agricultural by-products treatment.