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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. [ABSTRACT FROM AUTHOR]

A method for determining the total solids and fat content of liquid whole egg products based on the principle of transformer was developed. The electrical parameters (terminal voltage and λ value) in the secondary circuit, where the sample acted as the coil, were investigated under the action of alternating magnetic flux in the frequency range from 60 to 400 Hz. Findings indicated that subtle changes of quality indices could be detected by electrical parameters based on the transformer properties that relate to the amount of free ions in the samples. As the inductive voltage was fixed, terminal voltage was negatively correlated with quality indices of total solids and fat content. Therefore the decrement of impedance in the secondary circuit caused the increment of inductive current according to Ohm's law. Linear prediction models for the aforementioned quality indices based on these electrical parameters were also established. Judging from coefficients of determination ( R 2 ) and the root mean square error of prediction (RMSEP) of these models, the λ value was found to be a better predictor for quality indices of liquid whole egg products than terminal voltage. It is believed that this method has the potential to evaluate the quality of liquid food materials over a wider frequency and temperature range. [ABSTRACT FROM AUTHOR]

The study proposes a method for measuring the electrical properties of orange juice by using two magnetic fluxes with the same frequency (or synchronous magnetic fluxes) at 400–700 Hz. The juice was passed through two spiral glass tubes, which formed the secondary coils of the transformer with different connection modes. Five measurement points ( a , b , o , − a , and − b ) were arranged at different terminals of the two coils to evaluate output voltages ( U − aa , U oa , U − bb , and U ob ) under the fluxes. Control parameters included the excitation voltage ( U P ), frequency, and phase difference. Results indicated that the output voltage of the juice increased linearly with increasing excitation voltage at all points. In-phase output voltages were higher than reverse-phase output voltages. The value for λ − aa ( U − aa / U P ) remained stable as the excitation voltage increased. In addition, different physicochemical properties of orange juice caused a change in the output voltages, which was consistent with Ohm's law . Soluble solids content and U − bb were linearly correlated, showing R 2 values at 0.875 and a root-mean-square error of 0.702 Brix° at 20 V and 700 Hz. The method showed potential for the rapid determination of the quality of liquid foods by using magnetic flux-induced electrical parameters. [ABSTRACT FROM AUTHOR]