Effect of radiofrequency assisted freezing on meat microstructure and quality

The potential exploitation of radiofrequency (RF) to assist food freezing was studied. To this aim, freezing of pork meat was performed in a RF pilot equipment modified to allow food immersion in a liquid nitrogen spray. During freezing, pulsed RF treatments were applied (RF assisted cryogenic freezing). Freezing under cryogenic fluid flow (cryogenic freezing) and air freezing were also performed as controls. Results showed that RF assisted freezing is possible by using low voltage pulses (2 kV). The thawing losses of RF cryogenic frozen meat were much lower than that observed during thawing of air and cryogenic frozen meat, which showed similar drip loss. The analyses carried out on the microstructure of meat showed that the tissue exhibited a better cellular structure when RF was applied. Much less intercellular voids and cell disruption were observed. As compared to the control sample, RF frozen meat presented smaller ice crystals, which were mainly located at intracellular level. This was attributed to the ability of RF to depress the freezing point thus producing more nucleation sites.