Treatment and Post-Mortem Aging Effects on the Z-line of Myofibrils from Chicken Pectoral Muscle

SUMMARY: Changes in the morphology of myofibrils prepared from chicken pectoral muscle during post-mortem storage at 5°C were examined by light and electron microscopy. When the 24-hr stored samples were blendorized, electron micrographs showed two types of destruction in the Z-lines of sarcomeres and myofibrillar fragments: (1) The degradation and/or disappearance of Z-lines. (2) The breakdown of the junction of Z-line and I-filaments. A change in the state of the Z-line and the junction of the Z-line and I-filaments appeared to be indispensable for the fragmentation of the myofibrils. It was also shown through phase contrast microscopic observations that sarcoplasmic proteins, participating in the glycolytic cycle, may play a role in the fragmentation of the myofibrils. Evidence has not been obtained, to date, on the participation of proteolytic enzymes in the fragmentation phenomenon.     

Relationship Between Fragmentation of Myofibrils and Liberation of Phospholipids from Z-Disks Induced by Calcium Ions at 0.1 mM: Mechanism of Tenderization of Pork and Beef during Postmortem Aging

ABSTRACT We studied the myofibril fragmentation using porcine and bovine myofibrils to determine the mechanism by which myofibrils are fragmented during postmortem aging of meat. Both myofibril fragmentation and liberation of phospholipids from Z-disks were maximally induced by calcium ions at 0.1 m M . These phenomena showed identical dependencies on pH and temperature in the presence of calcium ions at 0.1 m M . All phospholipids in Z-disks, except for lysophosphatidylethanolamine, had affinity for calcium ions. Therefore, we concluded that liberation of calcium-phospholipid compounds from Z-disks causes weakening of the Z-disk structure, resulting in the myofibril fragmentation during postmortem aging of meat.     

EFFECTS OF PHYSICAL PROPERTIES AND ORAL PERCEPTION ON TRANSIT SPEED AND PASSING TIME OF SEMILIQUID FOODS FROM THE MID-PHARYNX TO THE HYPOPHARYNX

The results of two sensory analyses, using healthy young individuals as assessors and semiliquid foods with markedly different physical properties as samples, were compared. One analysis required the assessors to perceive the food texture by oral perception alone and to use it as a basis for predicting the ease of swallowing of the bolus samples (i. e., the mobility of the samples through the pharynx) without actually swallowing the samples. The other analysis required the assessors to evaluate the mobility of the bolus samples through the pharynx, by actually swallowing them. Comparison of the results implied that human beings predict how easy it is to swallow a bolus (i. e., the mobility of the bolus through the pharynx) by perceiving in the oral cavity the texture of the food. Examinations were also made on the relationship between the evaluation of mobility of the bolus through the pharynx obtained by sensory analyses, and the transit speed and passing time of the bolus samples obtained by videomanofluorography. It was recognized that the front end speed was fast for semiliquid food samples that were soft and easy to swallow (and therefore easy to move through the pharynx), whereas the front end speed was slow for semiliquid food samples that were hard and difficult to swallow (and therefore perceived as being difficult to move through the pharynx.) These findings suggest that human beings' perception of the ease of swallowing of semiliquid food is closely related to the front end speed of the bolus. No significant difference was found among samples, either in the tail end speed of the bolus samples, or in the passing time from the front end to the tail end of the bolus samples. These results imply that, through some kind of swallowing efforts, healthy individuals are controlling the passing time through the pharynx of boluses with markedly diflerent physical properties, so that the time remains constant.