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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]