EFFECTS OF ULTRASOUND AND CONVECTION COOKING TO DIFFERENT END-POINT TEMPERATURES ON COOKING CHARACTERISTICS, SHEAR FORCE AND SENSORY PROPERTIES, COMPOSITION, AND MICROSCOPIC MORPHOLOGY OF BEEF LONGISSIMUS AND PECTORALIS-MUSCLES

Longissimus and pectoralis muscles were removed from 10 steer carcasse s at 4 d postmortem, aged for 14 d at 2 degrees C, then assigned to ei ther ultrasound or convection cooking to either 62 degrees C or 70 deg rees C internal end point temperature. During cooking, time-temperatur e profiles and energy consumption were monitored. Ultrasound cooking r esulted in greater (P < .05) cooking speed, greater (P < .05) moisture retention and less (P < .05) cooking loss, greater (P < .05) efficien cy of energy consumption, a more uniform cooking environment, and less (P < .05) instrumental peak-force work to shear muscle samples than c onvection cooking. The ultrasound treatment also resulted in a reducti on (P < .05) in soluble collagen content and superior (P < .05) myofib rillar tenderness, as determined by a trained sensory panel, than conv ection cooking. Electron micrographs indicated that ultrasound-cooked muscles had longer sarcomeres, larger diameter fibers, and more myofib rillar disruption and shattering. Longissimus muscles cooked faster (P < .05) and more (P < .05) energetically efficient, had less (P < .05) total collagen, and were superior(P < .05) in instrumental evaluated texture and sensory tenderness than pectoralis muscles. Cooking to 70 degrees C caused greater (P < .05) moisture and cooking losses, requir ed more (P < .05) time and energy input to cook, and negatively (P < . 05) affected instrumental textural and sensory tenderness characterist ics. Electron micrographs indicated a shortening of sarcomeres, more d eterioration of the banding structure, reduction in fiber diameter, an d breakdown of endomysial and perimysial connective tissue at an inter nal temperature of 70 degrees C vs 62 degrees C. This research identif ies ultrasound cooking as a new, rapid, energy-efficient method that m ay improve some meat textural attributes.