THE EFFECTS OF DELAYED CHILLING AND ALTERED CARCASS SUSPENSION UPON BEEF MUSCLE: II. HISTOLOGICAL AND CHEMICAL PROPERTIES

A total of 60 bovine carcasses from “exotic”— crossbred heifers, 12 to 16 months of age with carcass weights of approximately 260 kg were utilized in two separate but related experiments to evaluate the effects of delayed chilling at 2 temperatures (13 and 22°C) for 12 or 24 h and altered carcass suspension on certain histological and chemical properties of beef muscle. Hip-free suspension (suspension by the os coxae from hooks inserted through the obturator foramen with the limbs hanging free) produced substantially greater alteration of the histological properties of the muscles evaluated than did delayed chilling. Such alterations resulted in longer semimembranosus (SM) and longissimus dorsi (LD) sarcomeres, shorter psoas major (PM) sarcomeres, smaller SM and LD muscle fiber diameters, larger PM muscle fiber diameters, fewer SM and LD wavy fibers, more PM wavy fibers, and shorter SM muscle fiber fragment lengths (P<0.05). Neither hip-free suspension nor delayed chilling produced consistent differences (P<0.05) in either the intramuscular collagen content, the heat solubility of the intramuscular collagen, or the histological properties of the intramuscular collagen fibers.