A strategy for improving the uniformity of radio frequency tempering for frozen beef with cuboid and step shapes

Abstract

Radio frequency (RF) tempering is considered as a fast and volumetric heating technology and has been proved to be effective in meat tempering. However, the thermal runaway heating problem usually causes uneven heating at the sample edges. In this study, a newstrategy whereby the frozen meat was surrounded by selected medium was developed and evaluated in order to improve the tempering uniformity. The RF tempering uniformity improvement effects of crushed ice, ethanol solution and glycerol solution were tested with frozen minced beef with two shapes: a cuboid and a step-shape, which were reported to experience the worst tempering uniformity in RF field. The temperature/time history, temperature distribution, cook loss, total volatile basic nitrogen (TVBN) and color indexes were determined and compared after RF tempering, RF tempering with glycerol solution surrounding, and refrigeration tempering treatments. Glycerol solution (70%) was verified to be the most effective surrounding medium, which improved the tempering uniformity significantly, and also was non-toxic, non-flammable and free from odor. The temperature variation within the volume of a step-shaped beef sample was −3.7∼-5.3 °C. The beef quality attributes of RF tempering with glycerol solution surrounding the sample were the highest, and were found to be similar to those after refrigeration tempering. The RF tempering rate with immersion in glycerol solution was 40 times higher than the traditional refrigeration tempering method. Results in this study indicate that 70% glycerol solution could be an effective surrounding medium for frozen meat products in RF tempering uniformity improvement.