Water distribution and mobility in meat during the conversion of muscle to meat and ageing and the impacts on fresh meat quality attributes--a review.

Toughness development in beef sternomandibularis muscle during cooking has been measured by a tenderometer, cleaving samples at right angles to the fibre direction. Since the muscles had been set in rigor mortis in an unshortened state, such toughening was not related to that induced by pre-rigor contraction.



Two distinctly separate phases of toughening develop with increasing cooking temperature. A three- to fourfold toughening occurs in the first cooking phase between 40 and 50 oC, followed by a further doubling in the second phase between 65 and 75 oC. The first phase is associated with loss of myosin solubility, presumed to indicate denaturation in the contractile system. The second is closely associated with collagen shrinkage. This apparently induces shortening along the meat fibre, forcing out meat juice.

Temperature-dependent cooking toughness in beef

Publisher Summary This chapter discusses that the unique features of connective and skeletal tissues are their diversity and morphological character. Morphologically, connective tissue consists of fibrous proteins, ground substance, and cells. Before 1970, all vertebrate collagens were regarded as a simple class of molecules composed of two α1chains and one α2 chain, with only minor heterogeneity in composition between species. Collagen, a glycoprotein, is the longest of all protein molecules and is composed of tropocollagen monomers which are 300 nm long and 1.5 nm in diameter. The chapter discusses that twenty or twenty-one different amino acids are known to be present in different collagen types. The synthesis of a protein in living cells involves placing the amino acids in the proper sequence, determined by the genetic code, and linking them together by α peptide linkages. The macromolecular components of collagen are synthesized in large part at a ribosomal-messenger RNA complex within the cytoplasm of a family of mesenchymal cells, which include fibroblasts, chondroblasts, and osteoblasts. Proteins have no parallel in their structural and textural versatilities. The chapter discusses that although nature has designed proteins to perform specific roles in situ, they can display multifunctional properties by appropriate manipulations and processing treatments in different food systems. Animal skins contain the bulk deposit of collagen, thus, byproducts of the tannery can be utilized in the commercial production of edible fibrous collagen.

Chemical, Biochemical, Functional, and Nutritional Characteristics of Collagen in Food Systems

Tenderization of buffalo meat using plant proteases from Cucumis trigonus Roxb (Kachri) and Zingiber officinale roscoe (Ginger rhizome)

SUMMARY— During the aging of fiber pieces prepared from bovine sternomandibularis muscles, a loss of adhesion occurs between adjacent myofibrils. This is evidenced by increased readiness of fiber pieces to distintegrate into individual myofibrils during a period of standard disruption. Alterations also appear within the myofibrils themselves in the regions of the Z lines, sometimes leading to the apparent dissolution of this structure. Ethylenediamine tetraacetate present in the suspensions during storage not only prevents these changes, but also preserves the refractory character of the fiber pieces. Meat aging is considered therefore to be due to disruption and possible dissolution of Z-line material, leading to a weakening of inter-myofibrillar linkages probably located at the junctions of adjacent Z lines, and to loss of tensile strength of the myofibrils themselves.

Studies in Meat Tenderness. 7. Changes in the Fine Structure of Meat During Aging

SUMMARY— Changes during aging in the extractability of the myofibrillar proteins of meat from beef and rabbit carcasses have been examined, using a buffer which dissociates the actomyosin complex of the muscle cell. Approximately 52% of the myofibrillar proteins of unaged meat is extracted in 40 min at 2°C whereas from aged meat as much as 78% is extracted.



The rate and extent of these changes are determined largely by the ultimate pH value of the meat. Similar increases in protein extraction, displaying the same pH dependence, occur during the aging of well-washed myofibrillar preparations.



The increase in the percentage of myofibrillar protein extracted during aging results from either a progressive weakening of the fibrous protein linkages with the insoluble stroma of the meat cell, or from a disintegration of the insoluble stroma itself.

C. L. Davey

Papers

Studies in Meat Tenderness.