The thermal denaturation of collagen the perimysium of intramuscular connective tissue isolated from bovine Semitendinosus (ST) and Perctoralis profundus (PP) muscles was investigated using a range of heating rates in differential scanning calorimetry (DSC) and analyzed by application of the Kissinger-Akahira-Sunose (KAS) and Lumry-Eyring models. Thermograms showed a broadening of endotherms and a shift towards higher temperatures as the thermal scanning rate increased. These features are consistent with the two-step process of a reversible transition between native and unfolded collagen molecules followed by an irreversible transition between unfolded and denatured states. There were small differences between muscles in the onset temperatures of the thermal transitions at heating rates of 0.5 K min^-1, while both the KAS and Lumry-Eyring models yielded similar values for the effective activation energy of the whole two-step process, the Lumry-Eyring model allowed a greater insight into differences in the reversible and irreversible steps between the perimysium both muscles. Reversible unwinding of the triple-helical collagen molecules in the perimysium from ST muscle required more energy than in PP muscle. It is speculated that the presence of large amounts of elastin in the perimysium of ST muscles may influence this due to a protein crowding mechanism, or by affecting the covalent cross-linking of the collagen.

Pigskin Treatment Using Different Food-Grade-Acids: Effects on The Physicochemical Characteristics of The By-Products

Animal tissue by-products, rich in collagen, represent a valuable source of biomaterials. Understanding their physicochemical and thermal behavior is essential for expanding their applications. In this study, pigskin gelatin was extracted through acid hydrolysis using a combination of acetic acid (AH) and either lactic, citric, or ascorbic acid (75:25, v:v, [0.5 M]), followed by thermal denaturation. We evaluated the physicochemical properties of the gelatin solutions (pH, hydroxyproline content, and extraction yield), as well as the macroscopic gel characteristics. Gelatin films were then prepared and analyzed for moisture content, color, and thermal properties. One-way ANOVA was applied to compare treatments, and Pearson’s correlation was used to assess the relationship between the solution pH and physicochemical parameters. Significant differences in the final pH of the solutions were observed among the acid mixture treatments, though the hydroxyproline content and extraction yield were not significantly affected. All gelatin solutions formed stable gels, and the resulting films exhibited similar moisture content. Thermal analysis revealed treatment-dependent variations. Specifically, a significant negative correlation (p < 0.005) was found between the gelatin solution pH and the melting temperature. These results suggest that the use of organic acid mixtures can effectively modulate gelatin properties, offering a versatile approach for tailoring biomaterials for both food and non-food applications.