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Crude calcium-activated factor (CAF) was prepared from pre-rigor pressurized (PRP) and corresponding control (CON) bovine muscles at 0, 1, and 3 days of postmortem times. Throughout these periods, PRP samples had consistently lower total CAF activity than CON. Yet, it seems probable that PRP caused a transient increase in Ca++ sufficient to activate CAF for a brief period of time because (1) early postmortem, PRP muscle had quantities of a 95,000-dalton component presumably produced by CAF; (2) Z-lines from at-death PRP muscles were highly degraded; (3) very early postmortem storage, the SDS-electrophoretic patterns of PRP myofibrils resembled that of CAF-treated myotibrils. CAF autolysis may account for the low CAF activity observed in PRP muscles at later postmortem storage times.

A 2x2 factorial experimental design with 2 replications was used to study the effects of a combination of electrical stimulation and delayed chilling of carcass on meat characteristics. Twenty Standard or Good grade beef cattle were slaughtered and 10 sides were assigned to each of the 4 treatments. Meat characteristics were evaluated subjectively (sensory panel evaluation) and objectively (W-B shear device). Electrically stimulated carcasses cooled faster in the first hour postmortem; thereafter the order of further cooling was reversed. The 24 hr postmortem weight loss in the electrically stimulated with delayed chilling did not differ (P > 0.05) from those receiving electrical stimulation plus immediate chilling nor those not stimulated but chilled immediately. For delayed chill carcasses, 24 hr postmortem weight loss was lower (P 0.05). At the microstructural level, an open triad and T-system were observed immediately following electrical stimulation. As early as 24 hr postmortem, considerable Z-line degradation was observed in the electrically stimulated and delayed chilled samples.

Sixty single-reared lambs sired by Hampshire rams were used to study the effects of monensin and ryegrass straw on feedlot performance. Two levels of monensin (0 and 27.5 ppm) and two levels of ryegrass straw (0 and 25%) were arranged in a 2 × 2 factorial treatment arrangement. Each of the four pelleted diets was fed ad libitum to 15 lambs. Monensin-fed lambs had lower (P 0.10), monensin-fed lambs also had improved feed efficiencies over lambs not fed monensin. Crude protein, ether extract and crude fiber digestibilities of the diets were increased by the addition of monensin. Lambs fed ryegrass straw had lower (P

The effect of hydrostatic pressurization of pre-rigor beef round muscle (semitendinosus) on protein quality was biologically and chemically determined. For biological evaluation rats (Long-Evans strain) were used. Chemical evaluation was carried out by amino acid analysis. The biological and chemical protein efficiency ratios (PER) of pressurized meat were 2.47 and 2.7, respectively, compared to 2.60 and 2.84 for the control meat. Pressurization did not affect the apparent biological value (BV) or net protein utilization (NPU) of meat but significantly (P < 0.05) improved protein digestibility. Total essential and nonessential amino acid contents of pressurized samples were not different from that of the control. At the range tested, the protein quality of meat was not adversely affected by pressure treatment.

The emulsifying capacities of pressure treated and control muscle homogenates, sarcoplasmic protein and myofibrillar proteins of ovine and bovine longissimus muscles were determined at 2, 6, 24 and 168 hr postmortem. The pH of the intact muscle, muscle homogenate and myofibrillar protein extract were taken at these times. Before onset of rigor mortis, the emulsifying capacity of muscle homogenate from the control samples was higher than the pressure treated samples. At 24 and 168 hr postmortem, the pressure treated and control samples were not significantly different (P>0.05) for emulsifying capacity. At 2 hr postmortem, the emulsifying capacity of myofibrillar protein extract from control samples was higher (P

Semimembranosus muscle was excised immediately following slaughter and pressurized at 103.5 MN−2 for 2 min at 35°C. Creatine phosphate (CP), adenosine-5′-triphosphate (ATP) and R-values (a measure of metabolic rate) were determined at 1, 2, 4, and 24 hr postmortem. Creatine phosphokinase activity (CPK) was measured at 1 and 24 hr postmortem. Pressurization accelerated catabolism of both CP and ATP which, in turn, resulted in a higher ATP turnover value than that of the control. R-values were significantly correlated (r=−0.95) with degradation of ATP and indicate onset of rigor mortis in treated muscle immediately after pressurization. CPK activity was significantly higher (P

Prerigor bovine semimembranosus muscle was pressure-treated at 103.5 MNm-2 (15.000 psi) for 2 min at 37°C. Glycogen levels of pressurized muscle were significantly (P < 0.01) lower than those of the control at 1, 2 and 4 hr postmortem. Glucose concentrations were significantly (P < 0.01) higher in the treated muscle than in the control at all sampling periods. Lactate content increased rapidly after pressurization (1 hr postmortem); however, there was no significant difference between control and treated muscles at 24 hr. Pressurized muscle showed a significant (P < 0.01) increase in LDH activity over that of the control muscle at 1 hr, but not at 24 hr postmortem. Thus pressurization of muscle accelerated the rate of glycolysis and enhanced LDH activity.

Changes in myofibrillar proteins of bovine longissimus and semitendinosus muscles were examined during 14 days of postmortem storage at 2°C by SDS-Polyacrylamide gel electrophoresis. Major changes in both muscles were: (1) appearance of a 95,000-dalton component; (2) gradual disappearance of troponin-T and gradual appearance of a 30,000-dalton component; (3) gradual increase in intensity of a protein around 55,000-daltons; and (4) gradual appearance of a 110,000-dalton component. With the exception of the 95,000-dalton component, the other changes have been reported previously by other authors. At the present time we have no knowledge of the origin of the 95,000-dalton component, but it is known that calcium-activated factor (CAF) is responsible for degradation of troponin-T. Appearance of the 95,000-dalton component during postmortem storage suggests involvement of CAF for increasing tenderness during postmortem storage.