Study of Radio Frequency Thawing for Cylindrical Pork Sirloin

Abstract

Purpose: Radio frequency (RF) heating is a promising thawing method, but it frequently causes undesirable problems such as non-uniform heating. This can occur because of the food shape, component distribution, and initial temperature differences between food parts. In this study, RF heating was applied to the thawing of cylindrically shaped pork sirloin by changing the shape of electrodes and the surrounding temperature. Methods: Curved electrodes were utilized to increase the thawing uniformity of cylindrically shaped frozen meat. Pork sirloin in the shape of a half-circle column was frozen in a deep freezer at -70℃ and then thawed by RF heating with flat and curved electrodes. In order to prevent fast defrosting of the food surface by heat transfer from air to the food, the temperature of the thawing chamber was varied by -5, -10, and -20℃. The temperature values of the frozen pork sirloin during RF thawing were measured using fiber-optic thermo sensors. Results: After multiple applications of curved electrodes resembling the food shape, and a cooled chamber at -20℃ the half-cylindrically shaped meat was thawed without surface burning, and the temperature values of each point were similarly increased. However, with the parallel electrode, the frozen meat was partially burned by RF heating and the temperature values of center were overheated. The uniform heating rate and heat transfer prevention from air to the food were crucial factors for RF thawing. In this study, these crucial factors were accomplished by using a curved electrode and lowering the chamber temperature. Conclusions: The curved shape of the electrode and the equipotential surface calculated from the modeling of the parallel capacitor showed the effect of uniform heating of cylindrically shaped frozen food. Moreover, the low chamber temperature was effective on the prevention of the surface burning during RF thawing

Effects of radio frequency, air and water tempering, and different end‐point tempering temperatures on pork quality

“…Results indicated that radio frequency tempering led to a relatively uniform temperature distribution in lean meat, but resulted in a vastly large temperature difference in fat and lean meat blend. Kim et al () found that the edges and corners of cylindrical pork samples were over 20°C when to the center reached −4°C in a flat‐electrode radio frequency heating system. Curving the top flat electrode to fit the cylindrical pork sample could significantly improve the temperature uniformity.…”

Radio frequency thawing chamber for rapidly thawing applications

“…A model of frozen pork, whose relative permittivity is ε ′=20.4, 5 and dielectric loss factors set to ε ″=8, 9,10 has a length and width fixed at 150 and 100 mm, respectively. The thickness' variation range is 20 to 100 mm (corresponding to a mass variation range of approximately 220 to 1200 g) is employed in the simulation.…”

“…The operation frequency belongs to the ISM band, which can be used without application. 5,6 Moreover, the device which works in this frequency has an acceptable skin depth for frozen meat, so that the frozen meat can be heated rapidly and uniformly. Measurement results revealed that the thawing time was reduced from a maximum of about 8 hours to about 4 minutes compared with other three methods.…”

“…A novel RF thawing chamber has been designed, which overall size is 300 × 300 × 230 mm with a resonant frequency of 433 MHz. The operation frequency belongs to the ISM band, which can be used without application 5,6 . Moreover, the device which works in this frequency has an acceptable skin depth for frozen meat, so that the frozen meat can be heated rapidly and uniformly.…”

Effects of Radio Frequency Tempering on the Temperature Distribution and Physiochemical Properties of Salmon (Salmo salar)

“…Llave et al [ 22 ] discovered the RF tempering rate of tuna fish was three times higher than that with air tempering and that the best uniformity occurred with a top electrode projection similar in size to the sample. Kim et al [ 23 ] investigated RF tempering of pork with a curved-shape top electrode and found that temperature uniformity was improved by using a top electrode with a projection area smaller than that of the sample. Koray Palazoğlu et al [ 24 ] compared RF (27.12 MHz) and microwave (915 MHz) tempering of frozen blocks of shrimp (1.75 kg) and observed that localized overheating occurred in samples subjected to microwave tempering.…”