Sarcomere length of free and restrained bovine muscles at low temperature as related to tenderness

Abstract

Tenderness of semitendinosus and psoas major bovine muscles was markedly affected by: ( I ) allowing the muscle to undergo rigor mortis and the associated contraction, following pre-rigor excision, or by ( 2 ) pre-rigor excision followed by restraint in a stretched state while the muscle undergoes rigor mortis. The extent of stretch or contraction induced by pre-rigor treatment was reflected by the sarcomere length. The average sarcomere length of the semitendinosus and psoas major muscles differed widely when samples were removed post-rigor from the carcass. The data indicate that the state of contraction (measured by sarcomere length), when altered in different portions of the same muscle by treatment, or when varying naturally in different muscles, was associated with tenderness. IntroductionNumerous studies have been conducted during the past few years to determine the specific contribution of various factors to the tenderness of bovine muscle.l-12 One of the factors reported has been the difference in contraction state of myofibrils in bovine m~sc1es.l~ This worker postulated that the variations in sarcomere lengths among muscles, were due, in part, to the strains induced in the muscles when the carcass was vertically suspended, and also that since long sarcomeres occurred in muscles previously reported14 to be generally tender, the state of contraction was considered a factor contributing to tenderness, where the effect of connective tissue was small.Herring & Briskey5 noted that portions of bovine semitendinosus muscle, excised pre-rigor and stretched during cooking, were tender, while similar portions from the same muscle, excised and cooked in the free unrestrained state, shortened markedly and were tough.The present study was conducted in order to expand on the above general problem of tenderness and specifically to investigate further the report of Locker'3 which implicated muscular contraction in the problem of tenderness. Studies were made on different portions of the same muscle which were allowed to undergo rigor mortis under different experimental conditions in order to determine the relationships among contraction state, sarcomere length and tenderness.

Subcellular events associated with the development and release of isometric tension in post-mortem bovine, rabbit and porcine skeletal muscle

“…Moreover, psoas muscle, which is a very tender muscle, had con siderably longer sarcomere lengths than semiteiidinosus, which is nearly always less tender than the psoas. If the muscle was restrained to pre vent post-mortem shortening, a wide variation in sarcomere lengths was found, even though the muscle had been given & uniform treatment» These results of Herring e^ (1965) may be easily explained by Marsh and Leet's (1966) finding that, in muscle held at fixed length, different rates of cooling in different parts of the muscle cause the more rapidly cooled areas to shorten considerably, whereas other areas in the same muscle lengthen a compensatory amount. Fibers on the exterior of the re strained muscles in Herring's study probably underwent extensive shorten ing since they were cooled rapidly.…”

“…Shortening to less than 40% of rest length apparently causes disruption of Z-lines and other structural elements which hold the sarcomeres in proper juxtaposition; this results in increased tenderness. Marsh and Leet's (1966) findings also offer a simple explanation for the results of Herring ^ (1965). These investigators found that o o muscle excised pre-rigor and stored at either 1 or 5 had sarcomere lengths 50% shorter than muscle excised post-rigor, and furthermore that muscle excised post-rigor was always more tender than muscle excised pre-rigor.…”

“…Fibers on the interior of the muscle would not shorten to the same extent since they were not cooled as quickly post-mortem. This would cause the large variation in sarcomere lengths observed in these muscles by Herring et (1965).…”

Palatability and Selected Related Characteristics of Three Types of Roasted Porcine Muscle

“…It has been suggested that the tenderness of meat removed from the carcass in a pre-rigor condition is highly dependent upon the extent of the cold shortening that occurs after excision (Herring et al, 1965a;Marsh and Leet, 1966). Some muscles, including the LD, which is firmly anchored to the skeleton at one end only, are capable of shortening in the carcass under vertical suspension such as found in normal processing procedures because of tension release (Herring et al, 1965b;Marsh and Leet, 1966 and that sarcomere length is only an indication of molecular changes occurring in the actin and myosin of the muscle fiber (Herring et al, 1965a).…”

“…Some muscles, including the LD, which is firmly anchored to the skeleton at one end only, are capable of shortening in the carcass under vertical suspension such as found in normal processing procedures because of tension release (Herring et al, 1965b;Marsh and Leet, 1966 and that sarcomere length is only an indication of molecular changes occurring in the actin and myosin of the muscle fiber (Herring et al, 1965a). …”