Effect of collagen on technological quality of meat

Kolagen stanowi 20 - 30 % białek w organizmie ssaków oraz ptaków i jest podstawowym składnikiem śródmięśniowej tkanki łącznej. Głównym magazynem kolagenu w mięśniach jest omięsna zewnętrzna (epimysium) i wewnętrzna (perimysium) oraz śródmięsna (endomysium). Wśród ponad 20 typów genetycznych kolagenu w mięśniach szkieletowych znaczną część stanowi kolagen typu I i III. Morfologia, skład i ilość tkanki łącznej w mięśniach zależy w głównej mierze od ich typu oraz gatunku, rasy i wieku zwierzęcia. Różnice w metodach oznaczania kolagenu sprawiają, że zawartość tego białka w poszczególnych mięśniach może być zróżnicowana. Duża zawartość tego niepełnowartościowego białka w tkance łącznej mięśni ma znaczący wpływ na kruchość mięsa, obniżając jego jakość. Zwiększające się wraz z wiekiem zwierzęcia usieciowanie kolagenu w mięśniach o wysokiej aktywności za życia sprawia, że mięso staje się twarde. Mniejszą zawartość kolagenu stwierdzono w mięśniach o dłuższych sarkomerach oraz w mięsie ze zwierząt późno dojrzewających i wykastrowanych.Collagen constitutes 20 - 30 % of proteins in the organism of mammals and birds, and it is a major component of the intramuscular connective tissue. In the muscles, collagen is mainly stored in epimysium, perimysium, and endomysium. There are more than 20 genetic types of collagen in the skeletal muscles and, among them, collagen type I and type III are a significant portion. The morphology, composition, and quantity of the connective tissue in the muscles depend predominantly on their type, as well as on the species, breed, and age of the animal. Owing to differences in the methods of determining collagen, the content of this protein can differ in individual muscles. A high content of this incomplete protein in the connective tissue of the muscles has a significant impact on the tenderness of meat and decreases its quality. The cross-linking of collagen in the muscles that are highly active in live animals increases with age of animals and causes the meat to become hard. A lower content of collagen was found in the muscles with longer sarcomeres and in the meat from late maturing and castrated animals

Heme iron in meat as the main source of iron in the human diet

Iron is a trace element involved in many cardinal metabolic processes of almost all living organisms. It is well known that iron participates in oxygen transport as well as it is a cofactor in many fundamental enzymatic and nonenzymatic processes. Accordingly, disturbances of iron homeostasis can cause serious clinical consequences. In humans, dietary iron can enter the body in two main forms: heme and nonheme. The former is a component of many hemoproteins (including myoglobin, hemoglobin, cytochromes b and c) and is easily absorbed in the duodenal enterocytes. Red meat is an excellent source of heme iron, while the less bioavailable nonheme form is found in large amounts in milk products and vegetables. For this reason, consumers of meat have a better iron status than vegetarians and vegans. The aim of this paper was to discuss the role of heme iron in the human diet. Heme iron found in muscle protein should be supplied to humans to prevent iron deficiency, which can lead to anemia. It is easily absorbed by the human body and its main source is red meat. In addition, heme iron, which is mainly found in myoglobin in meat, contributes to the desirable bright red color and to the most undesirable brown color of meat. Both heme and nonheme iron are catalysts of lipid oxidation in meat. This process lowers the nutritive value through oxidation of polyunsaturated fatty acids, which produces an undesirable flavor and aroma. The present review is focused on the role of heme iron, which is mainly found in meat and is the principal source of iron in the human diet