THE EFFECT OF LOW-INTENSITY ULTRASOUND TREATMENT ON SHEAR PROPERTIES,COLOR STABILITY AND SHELF-LIFE OF VACUUM-PACKAGED BEEF SEMITENDINOSUSAND BICEPS FEMORIS MUSCLES

A series of experiments were conducted to assess the impact of low-int ensity ultrasound treatment on shear properties, color and shelflife o f packaged beef muscles. For the first experiment, 15 beef semitendino sus muscles were sliced (6.4 x 2.5 x 10.2 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 degrees C for 4 days; controls were not sonica ted. Muscles were then removed from vacuum bags, weighed, cooked to 70 degrees C internal temperature in a convection oven and evaluated for cooking and shearing properties. For the second experiment, 14 beef s emitendinosus muscles were sliced (2.5 x 5.1 x 10.2 cm), vacuum packag ed and allocated to either a simultaneous ultrasound/water-bath-heatin g treatment or water-bath-heating treatment only. Muscles were removed from the water-bath when the water temperature reached 70 degrees C, removed from the vacuum bags, cooked further to an internal temperatur e of 70 degrees C in a convection oven and evaluated for instrumental shear. For the third experiment, 30 beef biceps femoris pieces (1.3 x 7.6 x 10.2 cm) were mixed together to more evenly distribute native mi croflora, vacuum packaged and allocated to either ultrasound (1.55 W/c m(2), 3 degrees C, 30 min) treatment or control (no ultrasound treatme nt). Vacuum-packaged muscles were stored in a retail display case (3 d egrees C) and evaluated at 0, 5, 10, 20 and 30 days for microbial coun t and instrumental color (CIE La*b*). Ultrasound had no effect (p > 0 .05) on storage purge loss, cooking loss, or textural properties (Expe riments I and 2). Microbial levels were initially reduced (p < 0.05) b y the ultrasound treatment (0 days), but differences in microbial numb ers between ultrasound-treated samples and controls disappeared (p > 0 .05) during storage (Experiment 3). (C) 1996 Elsevier Science Ltd.