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Influence of Various Adrenergic Accelerators and Blocking Agents upon Glycolysis and Some Related Properties of Sheep Muscle

Meat Industry Research Institute of New Zealand and the Ruakura Agricultural Research Centre,^,4 Hamilton, New Zealand

Abstract

FOUR experiments are reported in which ante-mortem injection of epinephrine, propranolol and reserpine, and CO₂ anesthesia were investigated for their effects upon glycolysis, tenderness and some related properties of sheep muscle. In order to determine the effectiveness of the various treatments, one side of each carcass was early frozen (–30 C at once) and the other was conditioned (15 C for 24 hr.) before freezing.

Epinephrine did not significantly alter glycolysis or the other muscle properties, although panel tenderness scores for treated muscles were somewhat tougher than controls (approached significance). The stress of handling and slaughtering appeared to produce sufficient stimulation so that injection of added epinephrine did not measurably alter glycolysis. This was supported by the fact that the adrenergic blockers, propranolol and reserpine, resulted in significantly slower glycolytic rates and higher 24 hr. pH values than controls (P<.05).

Propranolol did not significantly influence tenderness or cold shortening. Reserpine, however, materially improved the tenderness of early frozen carcasses. Since cold shortening was not impaired in the reserpine-treated muscles, it is suggested that their greater tender ness may be due to higher pH values. CO2 anesthesia accelerated glycolysis and improved the tenderness of early frozen muscle, which suggests it may be used to reduce the length of the conditioning period before freezing.

Overall results substantiated previous studies showing that early freezing has a deleterious effect upon tenderness, which could be overcome by conditioning. It was also observed that the LD muscle was significantly more tender and juicy than the SM muscle (P<.01).

¹ The senior author was on sabbatic leave from the Department of Food Science and Human Nutrition, Michigan State University, East Lansing. He gratefully acknowledges the financial assistance provided by a Senior Research Fellowship through the Fulbright-Hays Program.

² Meat Industry Research Institute of New Zealand (Inc.), P. O. Box 617, Hamilton, New Zealand.

³ Ruakura Agricultural Research Centre, Private Bag, Hamilton, New Zealand.

⁴ The authors acknowledge the assistance of Dr. A. H. Kirton, Mr. Colin Burns and others of the abattoir at the Ruakura Agricultural Research Centre for providing the animals and slaughtering them. Acknowledgement is also made to Dr. W. G. Whittlestone, Dr. R. A. S. Welch and Dr. R. Kilgour of the Ruakura Agricultural Research Centre, and to Dr. C. L. Davey of the Meat Industry Research Institute of N. Z. (Inc.) for their interest and suggestions during the course of the work reported herein.