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Histochemical and Palatability Properties of M. Longissimus from Stress-Resistant and Stress-Susceptible Porcine Animals

Iowa State University³, Ames 50010

Abstract

Three groups of porcine animals (fat, stress-resistant; muscular, stress-resistant; and muscular, stress-susceptible) were used to determine certain chemical, histochemical and organoleptic properties of the M. longissimus. Blood pH after physical stress was significantly lower in the muscular stress-susceptible group than in the other two groups. No significant differences for moisture, fat, protein, ATP, CP and total creatine could be detected among groups. Four enzyme specific stains, phosphorylase, NADH-TR and acid and base stabile ATPase, were used for histochemical determination of red, white and intermediate muscle fiber types. Red fiber percentages were accurately determined either by ATPase stains examined together or by phosphorylase and NADH-TR stains examined together, whereas intermediate and white fiber percentages varied considerably between the two reciprocal staining methods. The fat stress-resistant group had significantly fewer red fibers (base-stabile ATPase) and more intermediate fibers (acid-stabile ATPase) than the two muscular groups. No significant group differences were found for bundle area, red fiber area, white fiber area, or individual fiber sizes. Furthermore, no significant differences were noted for organoleptic attributes and W-B shear values among groups. Although there were definite phenotypic and genotypic differences, such as fatness, muscularity, nervousness and other stress symptoms, it does not seem from this study that these characteristics are related to fiber type or palatability.

² John Morrell and Co., Elmhurst, Illinois.

³ Departments of Animal Science and Food Technology.

The assistance of Dr. M. H. Stromer, Mrs. B. E. Miner and Mrs. S. A. Josephson is gratefully acknowledged.