The Solubility of Intramuscular Collagen in Meat Animals of Various Ages

The mechanism for the promotion of tenderness in meat during the post-mortem process: a review

The post-mortem changes in the chemical composition and structure of striated muscle have been reviewed on the basis of various concepts that emerged from the studies of different investigators to explain the course of tenderization of meat during aging. These concepts include the changes in the sarcoplasmic proteins, myofibrillar proteins (such as complete dissociation of actomyosin, partial dissociation of actomyosin, cleavage of disulfide linkages, depolymerization of F-actin filaments, cleavage of myosin filaments, disorganization of Z-bands and the troponin-tropomyosin complex), sarcolemma, connective tissue elements (collagen fibrils, ground substance), and the protein-ion relationship of the muscle cells (more strictly, syncytia). The experimental evidence for and against each of the views is discussed critically in the light of certain fundamentals of biophysical chemistry and biochemistry. Finally, an alternative hypothesis has been presented based on the differential effect of the post-mortem formation of lactic acid (H+ ion concentration) on the intra- and extracellular components of muscle and the possible role of lysosomal cathepsins. Consequently, a series of biophysical, biochemical, and ultrastructural changes seem to account for the mechanism by which meat becomes tender during the aging process.

The effect of sex, dietary energy, meat protein, ascorbic acid and iron on broiler skin collagen

Two studies were conducted to determine if variation of sex, dietary energy, meat protein, ascorbic acid or iron had any effect on collagen metabolism in broilers. In the first experiment day-old broiler type chicks were fed diets which contained 3190 or 3410 kcal. M.E./kg. of diet, 0 or 15% meat and bone meal and 0 or 1 g./kg. ascorbic acid. In the second experiment the day-old broiler chicks were fed diets which had 3190 or 3410 kcal. M.E./kg. of diet and 60 or 260 p.p.m. of iron. At 56 days of age the broilers were weighed, a representative number of birds killed from each group and skin samples collected. The skin samples were analyzed for the degree of collagen cross-linking and the total and insoluble collagen contents. An alteration of energy, meat protein, ascorbic acid or iron in the diet had no effect on collagen formation in the skin of broilers reared in cool environmental temperatures. Female broilers had a significantly higher percentage of insoluble collagen in the skin tissue but the level of total collagen and insoluble collagen was higher in the male birds.