Molecular Properties of Post‐Mortem Muscle. 4. Effect of Temperature on Adenosine Triphosphate Degradation, Isometric Tension Parameters, and Shear Resistance of Bovine Muscle

Abstract

SUMMARY– Investigations were conducted on the effect of three storage temperatures, 2°, 16°, and 37°, on the changes and relationships of certain chemical and physical properties of post‐mortem bovine semitendinosus and psoas muscle. Post‐mortem muscle shortening was measured with the isometer. Isometric tension development was maximal at 2°, minimal at 16°, and at 37° tension was approximately one‐half that developed at 2°. The large tension development at 2° very likely originates from the same events as those in “cold shortening.” Differences in isometric tension parameters were noted between muscles in that psoas muscle developed tension and lost the ability to maintain tension more quickly than did the semitendinosus. Loss of ability to maintain tension was observed only at 2°, and this could correspond to a “resolution” of rigor mortis. Adenosine triphosphate (ATP) degradation was measured by two methods, ammonia production and bioluminescent enzymic method; the bioluminescent method proved to be the more satisfactory. A common relationship was observed between pH and ATP for both muscles and the three temperatures studied. No direct relationship was found between ATP degradation and shear resistance with the possible exception of muscle stored at 37°. Isometric tension parameters and shear resistance were related somewhat at 2° in semitendinosus muscle, but no relationship existed at 16° and 37°. Although considerable tension developed in psoas and semitendinosus muscle at 37°, shear resistance values decreased continuously, indicating that factors other than shortening are more important at high temperature and that these factors are temperature‐dependent. The role of ATP degradation in tension development was difficult to interpret, since at 2°, only a small change occurred in ATP level during large tension development, and the level of ATP at 2° did not differ from ATP level in muscle stored at 16° which developed little tension. Differences in post‐mortem muscle shortening at 2 and 37 are discussed.

Molecular Properties of Post‐Mortem Muscle. 6. Effect of Temperature on Protein Solubility of Rabbit and Bovine Muscle

“…Similarly, since post-mortem shortening of bovine muscle is greatest at 2" and least at 16" (Busch et al, 1967) and since myofibrillar protein solubility of bovine muscle at these two post-mortem storage temperatures is almost identical, it would appear that there also is no direct relationship between sarcomere length and myofibrillar protein solubility. Again, this conclusion is substantiated by the similar myofibrillar protein solubility of the psoas (average sarcomere length of 3.8 p) and the semitendinosus (average sarcomere length of 2.4 p) (Herring et al, 1965).…”

“…Bovine muscle stored at 37" is considerably more tender at 12 hr post-mortem than muscle stored at either 2" or 16" for a similar period (Busch et al, 1967), but this increased tenderness is not accompanied by an increase in myofibrillar protein solubility at 37"; indeed solubility in 1.1 M KI actually decreases at 37".…”

“…Work in our laboratory has demonstrated that post-mortem muscle loses the ability to maintain isometric tension after 24-# hr post-mortem (Busch et al, 1967;Jungk et al, 1967). This loss of tension development could result from either "depolymerization" of F-actin or a weakening of the actin-myosin interaction.…”

“…Temperature has been shown to have a significant effect on shortening and isometric tension development of post-mortem muscle (Busch et al, 1967;Galloway et al, 1967;Locker et al, 1963) and on in vitro contractile properties of actomyosin (Levy et al, 1962 ;Maruyama et al, 1964). Busch et al (1967) and Marsh et al (1966) demonstrated that temperature also markedly affects postmortem tenderness changes in beef.…”

Molecular Properties of Post‐Mortem Muscle. 7. Changes in Nonprotein Nitrogen and Free Amino Acids of Bovine Muscle

“…Despite the impressive amount of research concerning proteolysis, little relationship has been found between extent of proteolysis and tenderness in either beef (Husaini et al, 1950a,b;Wierbicki et al, 1956;Locker, 1960;Davey et al, 1966) or poultry (Miller et al, 1965), although Khan et al (1964) suggested that proteolysis affects tenderness. Storage at 2" and 16" has a profound effect on postmortem muscle shortening (Locker et al, 1963 ;Busch et al, 1967) and post-mortem tenderization (Busch et al, 1967). However, post-mortem storage at these two temperatures apparently does not affect the rate of ATP degradation and pH decline (Cassens et al, 1966 ;Busch et al, 1967)) protein solubility (Chaudhry et al, 1969)) or ATPase activity of myofibrils prepared from post-mortem muscle (Go11 et al, 1967;Robson et al, 1967).…”