The effect of low-intensity ultrasound treatment on shear properties, color stability and shelf-life of vacuum-packaged beef semitendinosus and biceps femoris muscles.

A series of experiments were conducted to assess the impact of low-intensity ultrasound treatment on shear properties, color and shelflife of packaged beef muscles. For the first experiment, 15 beef semitendinosus muscles were sliced (6.4 × 2.5 × 70.2 cm) weighed, vacuum packaged, subjected to a 1.55 W/cm(2) intensity ultrasonic field for 8, 16 or 24 min then stored at 3 °C for 4 days; controls were not sonicated. Muscles were then removed from vacuum bags, weighed, cooked to 70 °C internal temperature in a convection oven and evaluated for cooking and shearing properties. For the second experiment, 14 beef semitendinosus muscles were sliced (2.5 × 5.1 × 10.2 cm), vacuum packaged and allocated to either a simultaneous ultrasound/water-bath-heating treatment or water-bath-heating treatment only. Muscles were removed from the water-bath when the water temperature reached 70 °C, removed from the vacuum bags, cooked further to an internal temperature of 70 °C in a convection oven and evaluated for instrumental shear. For the third experiment, 30 beef biceps femoris pieces (1.3 × 7.6 × 10.2 cm) were mixed together to more evenly distribute native microflora, vacuum packaged and allocated to either ultrasound (1.55 W/cm(2), 3 °C, 30 min) treatment or control (no ultrasound treatment). Vacuum-packaged muscles were stored in a retail display case (3 °C) and evaluated at 0, 5, 10, 20 and 30 days for microbial count and instrumental color (CIE L (∗)a (∗)b (∗)). Ultrasound had no effect (p > 0.05) on storage purge loss, cooking loss, or textural properties (Experiments 1 and 2). Microbial levels were initially reduced (p < 0.05) by the ultrasound treatment (0 days), but differences in microbial numbers between ultrasound-treated samples and controls disappeared (p > 0.05) during storage (Experiment 3).