Search

The continuous-flow pasteurization apparatus was presented, and the electric field within orange juice was produced via an oscillating magnetic field at 50 kHz, causing the volumetric heating of the juice with initial conductivity of 6.85 mS/cm and 8.76 mS/cm. The process principle, especially numerical relationships between excitation voltage, magnetic field, induced electric field (IEF), induced current density, and temperature profile were elaborated. When applying a rectangular wave of the voltage at 50–1000 V, the waveforms of the magnetic field and IEF in the juice were sine-like and sawtooth waves, respectively. Through electromagnetic simulation, the model was established, which indicated the indirect heating of orange juice via oscillating magnetic field was feasible. As the magnetic field increased, the outlet temperature and induced current density in the juice was improved. Notably, the 4–5 logs CFU/ml inactivation effects on aerobic bacteria, yeast and mold in orange juice could be achieved at 65 °C for 60 s after the treatment. • Engineering characteristics of induced electric field technology was elaborated. • Electromagnetic simulation model was conduced to verify its thermal effect. • Waveform of magnetic field and induced electric field was investigated. • Difference between experimental and predicted temperature was not significant. • Inactivation effects on aerobic bacteria, yeast and mold was achieved. [ABSTRACT FROM AUTHOR]

A disposable continuous-flow system was established by treating apple juice with induced electric field (IEF). Under synchronous alternating magnetic flux, rather than electrodes, the electrical treatment was implemented in multi-series coils consisting of the flowing sample. An activation effect at 50 °C and inactivation effect at 70 °C were observed under IEF. High excitation voltage (900 V) caused a significant decrease in the residual activities (RA). As the flow rate decreased from 87.5 to 17.5 mL/min, RA of PPO and POD were changed without applying IEF indicated shear effect of the pump had an impact on the RAs. At 17.5 mL/min, PPO was inactivated after IEF treatment for 7.6 min. In compared with the control (0 V), the fluid impedance was increased at 70 °C and 80 °C under IEF, whereas it was decreased at 30 °C and 40 °C. IEF had no adverse influence on the color and volatile compounds of apple juice in this system. [ABSTRACT FROM AUTHOR]

An experimental impregnation system based on the inductive methodology was established and used to investigate the effect of electric fields on the calcium content of fresh-cut apples. An induced electric field was generated when the Ca 2+ solution acted as the secondary coil of the transformer system under the action of an alternating magnetic flux. The calcium content in fresh-cut apples was found to increase with the enhancement of the excitation voltage. Additionally, samples immersed in a CaCl 2 solution exhibited a calcium content higher than those suspended in the calcium lactate solution. The latter presented a higher load power factor, the impedance in the CaCl 2 solution being lower. Frequency at 20–60 kHz had a negative impact on the calcium content of fresh-cut apples due to the weakening of the electropermeabilization effect. This method utilized the conversion of electric energy into magnetic energy, and the electric field induced needing no insertion of powered electrodes into the solution under treatment. This might provide a reference for rapid impregnation of agricultural materials. [ABSTRACT FROM AUTHOR]

This study was aimed to establish a detecting system based on transformer method to evaluate moisture content and conductivity of egg albumen and yolks during storage. Results showed that the decrease in impedance of albumen and yolk resulted in the increase in the secondary terminal voltage during the eggs’ storage. Terminal voltage positively correlated with electric conductivity, regardless of frequency. The highest linear coefficient of determination (0.9955) between moisture content of yolk and terminal voltage at 50 Hz was observed. Exponential correlations emerged between the eggs’ conductivity and terminal voltage, with highest coefficient of determination ( R 2 = 0.8311 for albumen, R 2 = 0.9772 for yolk) at 200 Hz and 400 Hz, respectively. The correlations obtained in frequencies ranging from 50 to 400 Hz at 10 V laid the foundation for a method of evaluating moisture content and conductivity in albumen and yolks. Results facilitate an alternative application of the technique for rapid evaluation of the quality indices of liquid food products. [ABSTRACT FROM AUTHOR]

Kiwifruit juice is a popular liquid food with a large consumption. It usually needs high temperature sterilization before packaging and selling. Alternating magnetic field can produce alternating induced electric field, then a thermal effect is triggered. This study aims to explore the inner heating of kiwifruit juice via induced electric field and its impact on the physicochemical properties. Meanwhile, ultra-high temperature instantaneous sterilization (121°C, 5 s), and conventional heat treatment (93°C, 2 min) were conducted as controls, then effects were compared between these treatments. The results showed that the bacterial, mold and yeast colonies were completely eliminated, polyphenol oxidase activity decreased by 94.8%, and peroxidase activity decreased by 92.7%, at 1800 V and 6 mL/min. The induced electric field treatment and ultra-high temperature instantaneous sterilization had no significant effect on pH and titratable acid (P ≥ 0.05). Conventional heat treatment increased soluble solid content by 5.3%. The induced electric field treatment resulted in the closest color and browning index to the fresh juice owing to moderate thermal effect. It also demonstrated minimal loss on total phenols and flavonoids contents after induced electric field treatment (7.1% and 2.7%, respectively). The heating effect caused by induced electric field has great application potential for the treatment of fruit juice. • Induced electric field was utilized for direct heating of kiwifruit juice. • Contact-less thermal effect and temperature rise on kiwifruit juice was evaluated. • The microbe and enzyme could be inactivated within 7.7 s via continuous-flow treatment. • The minimal loss of total phenols and flavonoid was achieved via induced electric field. [ABSTRACT FROM AUTHOR]

The novel, previous unreported induction heating technique developed here uses the inverse process of the existing induction heating techniques. The theoretical basis for developing this technique is to determine whether the induced current passing through a winding food coil would induce a magnetic flux or cause an increase in primary current. Therefore, to develop this technique and implement it in the food industry, it is necessary to understand its technical details and engineering characteristics. This study presents the design and development process of the technique, as well as the calculation formulas, including load voltage, induced electric field, induced current density, heating power and energy utilization rate during the heating process. The results reveal that although the application of this innovative inner heating technique has been achieved, the energy efficiency of the current system is low. The thermal effect and non-thermal effect of the induced electric field decreased the total bacterial counts in the samples of grapefruit juice and raw milk. Image 10083 • Innovative induction heating is a sister technology to ohmic heating in the food industry. • Liquid food can act as the secondary winding of a transformer for inner heating. • A thermal effect on liquid foods by an alternating magnetic field was observed. • The development and design process of this novel technique are presented. • Continuous-flow pasteurization of liquid food was achieved by an induced electric field. [ABSTRACT FROM AUTHOR]