Meat tenderness studies : 1. Electrical stimulation-delayed chilling of beef carcasses. 2. Protein quality of pressurized meat

Graduation date: 1981A 2x2 factorial experimental design with 2 replications was\ud used to study the effects of a combination of electrical stimulation\ud and delayed chilling of pre-rigor muscle on meat characteristics.\ud Twenty Standard and Good grade beef cattle were slaughtered and 5\ud carcasses were assigned to each of the 4 treatments. Meat characteristics\ud were evaluated subjectively (sensory panel evaluation) and\ud objectively (W-B shear device). Other relative parameters were also\ud measured. Electrically stimulated carcasses cooled faster in the\ud first hr postmortem; thereafter the order of further cooling was reversed.\ud The 24 hr postmortem weight loss in the electrically stimulated\ud with delayed chilling did not differ (P > . 05) from those receiving\ud electrical stimulation plus immediate chilling nor those not\ud stimulated but chilled immediately. For delayed chill carcasses,\ud 24 hr postmortem weight loss was lower (P < . 05) in electrically\ud stimulated than in non-stimulated groups. Electrical stimulation\ud reduced (P < . 05) cooking losses. A further reduction (P < . 05) in\ud cooking losses was achieved by the electrical stimulation-delayed\ud chilling treatment. The difference in sarcomere lengths among the 4\ud treatments was not significant (P > . 05). At the microstructural\ud level, an open triad and T- system were observed immediately following\ud electrical stimulation. As early as 24 hr postmortem, considerable\ud Z-line degradation was observed in the electrically stimulated and\ud delayed chilled samples.\ud 2. PROTEIN QUALITY OF PRESSURIZED MEAT\ud The effect of hydrostatic pressurization of pre-rigor beef\ud round muscle (semitendinosus) on protein quality was biologically and\ud chemically determined. For biological evaluation rats (Long-Evans\ud strain) were used. Chemical evaluation was carried out by amino\ud acid analysis. The biological and chemical protein efficiency ratios\ud (PER) of pressurized meat were 2.47 and 2. 7 respectively, compared\ud to 2.60 and 2.84 for the control meat. Pressurization did not\ud affect the apparent biological value (BV) or net protein utilization\ud (NPU) of meat but significantly (P <. 05) improved protein digestibility.\ud Total essential and non-essential amino acid contents of pressurized\ud samples were not different from that of the control. At the range\ud tested, the protein quality of meat was not adversely affected by\ud pressure treatment