DEGRADATION OF INTRAMUSCULAR COLLAGEN DURING POSTMORTEM AGING (SOLUBILITY, SHRINKAGE, ISOLATION)
Abstract
Postmortem changes in structural and thermal stability and composition of intramuscular collagen were studied. Beef infraspinatus muscle samples were obtained from electrically stimulated and nonstimulated carcasses at 0, 1, 2, 4, 6, 8, 12 and 24 hr after slaughter. Epimysial connective tissue and separable intramuscular fat were removed from the samples before freezing in liquid N. Frozen samples were stored at -40(DEGREES)C. To isolate the intramuscular connective tissue (IMCT), the samples were warmed to ca. -3(DEGREES)C, then powdered in a Waring blender with dry ice. IMCT was recovered by screening the powdered muscle through a number 16 sieve (1.18 mm). Extraction yields and moisture, fat, protein and carbohydrate contents of isolated IMCT were determined. Collagen subunit composition of pepsin-solubilized connective tissue was determined using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). Thermal stability of the IMCT was determined by measuring the collagen thermal shrinkage temperature (T(,s)) using a differential scanning calorimeter. Structural stability of the IMCT was determined by measuring the amount of collagen solubilized in 1/4 strength Ringer's solution at 77(DEGREES)C. The yield of IMCT isolated from the infraspinatus samples and the carbohydrate content of that material did not change significantly (P > .05) during the 24 hr aging period. The collagen content and total protein content of the isolated IMCT increased (P < .05) through 8 hr. Moisture and fat contents of the isolated material decreased numerically but not significantly (P > .05) during the 24 hr aging period. SDS-PAGE of pepsin solubilized IMCT collagen components showed a nonsignificant increase (P > .05) in total collagen solubilized and in alpha components with time postmortem. Examination of individual alpha components revealed that, while all others were increasing, type III collagen components decreased in the isolated IMCT soon after slaughter. Total beta components and gamma component showed decreases which approached significance at the .05 level at 12 hr. Collagen T(,s) decreased (P < .01) and collagen solubility increased (P < .05) during the aging period with most of the changes occurring in the first 8 hr. Carcass electrical stimulation resulted in immediate reductions in thermal and structural stability of intramuscular collagen.
Degree
Ph.D.
Subject Area
Food science
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