Comparative Ultrastructure of Pectoralis Fibers from Electrically Stimulated and Muscle-Tensioned Broiler Carcasses

Transmission electron microscopy was used to study the ultrastructural changes induced by high voltage post-mortem electrical stimulation (ES) (440 V, 1 A, 5 pulses of 2 s on and 1 s off) and muscle tensioning (MT) (during chilling) in broiler chicken Pectoralis harvested at 1 h post-mortem. Control fibers lacked I-bands and H-zones. Electrical stimulation reduced sarcomere shortening and inhibited Z-line dissolution. Muscle tensioning pulled M-lines apart and allowed the disappearance of Z-line protein during aging. Combining ES and MT inhibited Z-line dissolution and caused wrinkling associated with passive contraction. All ES + MT fields had intact M-lines. The results suggested that there were similarities and differences in the ultrastructural effects of ES in broiler Pectoralis and red meat muscles.