Thermal transition of collagen in ovine connective tissues

Relationship between meat quality and intramuscular collagen characteristics of muscles from calf-fed, yearling-fed and mature crossbred beef cattle

Intramuscular Ehrlich Chromogen (EC) and pyridinoline (Pyr) concentrations in the gluteus medius (GM) and semitendinosus (ST) from crossbred Angus calf- (n = 14) and yearling-fed (n = 14) steer and mature cow (MC, n = 12) carcasses were related to collagen and intramuscular connective tissue (IMCT) thermal stability and peak Warner-Bratzler shear force (WBSF). In both muscles, Pyr density was greater in MC, while EC concentrations were comparable in calf- and yearling-fed steer muscles and lowest in MC muscles. Thermal denaturation temperature and enthalpy of IMCT were highest in both muscles when from MC, although only total collagen was correlated with WBSF in calf fed-yearling fed steer data. Results confirmed that EC concentration contributed to collagen thermal stability in steer muscles, but decreased it in MC muscles, while Pyr was consistently associated with collagen thermal stability.

The comparative research of structural and textural characteristics of six kinds of collagen-based sauce braised meat products

Collagen-based sauce braised meat products with a unique flavor, chewiness, and springiness are very popular in China. In order to understand how the structure, thermal properties, and chemical components of collagen-based tissues influence the texture characteristics of collagen-based meat products during stewing, three kinds of tendon tissues (chicken feet tendon [CFT], sheep tendon [ST], and bovine tendon [BT]) and three kinds of skin tissues (chicken feet skin [CFS], sheep skin [SS], and porcine skin [PS]) were selected to heat for 45 min at 95 °C, and texture, thermal properties, micromorphology, ultrastructure, glycosaminoglycan (GAG) content, and collagen content were evaluated among the six kinds of collagen-based tissues. Results showed that BT had the highest hardness, chewiness values, total collagen content, and the thickest fibers diameters, followed by ST, CFT, PS, and SS, whereas CFS had lowest values among six kinds of tissues. The thermal stability and GAG levels in tendon samples were higher than those in skin samples. Thicker diameters, higher thermal stability, GAG, and total collagen content could be responsible for the higher hardness and chewiness of tendon samples compared with skin tissues. These findings provide the understanding of relationship between meat quality of collagen-based meat products and their morphological and chemical properties. PRACTICAL APPLICATION: This research confirms that the difference in texture of different kinds of collagen-based tissues was related to the difference in structure and chemical properties. The result can be used to optimize the processing conditions of collagen-based sauce braised meat products in food industry.

Thermal stability of connective tissue from porcine muscles

Connective tissue of three porcine muscles (M. infraspinatus, IS; M. longissimus dorsi, LD; M. semimembranosus, SM) from 27 animals [populations A (n=13, reared in Ireland) and B (n=14, reared in Finland)] was studied by measuring the collagen content, collagen solubility and thermal shrinkage temperature of the connective tissue. Colour and pH were also determined. Collagen solubility was highest in IS (p<0.05) and lowest in SM (p<0.05) although no difference between LD and SM was found in population B. The onset and peak temperatures of thermal shrinkage (T(o) and T(p)) were highest in IS (p<0.05). The lowest T(o) and T(p) were found in SM from population B whereas no differences were seen between LD and SM muscles in population A. It was concluded that the thermal stability of the connective tissue in the three porcine muscles differ. IS, as a dark muscle has high thermal shrinkage temperatures and high collagen solubilities in comparison to the lighter LD and SM muscles which have lower thermal shrinkage temperatures and collagen solubilities. Collagen contents were highest in IS and lowest in LD.

Effect of thermal denaturation on water-collagen interactions: NMR relaxation and differential scanning calorimetry analysis

The dependence of the proton spin-lattice relaxation rate, and of the enthalpy and temperature of denaturation on water content, were studied by nmr and differential scanning calorimetry (DSC) in native and denatured collagen. Collagen was first heated at four different temperatures ranging from 40 to 70 degrees C. The percentage of denatured collagen induced by these preheating treatments was determined from DSC measurements. The DSC results are discussed in terms of heat-induced structural changes. A two-exponential behavior for the spin-lattice relaxation was observed with the appearance of denatured collagen. This was attributed to the presence of a noncollagen protein fraction. The variations in the different longitudinal relaxation rates as a function of the moisture content and of the denatured collagen percentage are described within the multiphase water proton exchange model. This study highlights the complementarity of the information obtained from the two analytical tools used.

Collagen crosslinks and their relationship to the thermal properties of calf tendons

The hydrothermal isometric tension and thermal transition temperature of collagen were determined in tendons from three different calf muscles. The levels of the nonreducible collagen crosslink, pyridinoline, and the collagen-associated Ehrlich chromogen were also measured in the three tendons. The reducible collagen crosslinks, hydroxylysinonorleucine, dihydroxylysinonorleucine, and histidinohydroxymerodesmosine were measured in two tendons. The thermal properties and levels of crosslinks were found to vary considerably between the different tendons, and also at different sites in two of the tendons. A strong correlation was observed between the thermal transition temperatures and the hydrothermal isometric tensions of the nine tendon sites examined. Both thermal properties correlated with the concentration of both pyridinoline and Ehrlich chromogen. The analogous behavior of the collagen-associated Ehrlich chromogen and the pyridinoline crosslink supports the role of the Ehrlich chromogen as a nonreducible crosslink.