Physicochemical, rheological, and functional evaluation of gelatins obtained from animal bones through acid-thermal hydrolysis for applications in biomaterials engineering

• Organic acids strongly control gelatin yield and quality from animal bone residues • Citric acid maximizes gelatin yield, especially from pig bones • Acetic acid improves gel clarity, strength, and texture properties • Bone source determines gelatin performance: pig ≥ beef > chicken • Results guide sustainable use of animal by-products in food applications The valorization of bone waste from the beef, pork, and chicken industries is an important strategy for utilizing byproducts rich in biopolymers, such as gelatin. This study examined how the organic acids citric, acetic, and lactic influence the yield and the physicochemical, rheological, and functional qualities of gelatin extracted from bone waste of pigs, chickens, and beef. The methodology involved stages of cleaning and thermal degreasing, demineralization with 5% acetic acid, and acid-thermal extraction using solutions of 3% (w/v) citric, acetic, or lactic acid at a solid–liquid ratio of 1:3, at 80–90°C for 4 hours. Variables such as yield, clarity, colorimetric parameters (CIE Lab* and h°), and rheological and functional properties were analyzed. The results showed that citric acid increased extraction yield, especially for pig gelatin, while acetic acid produced gels with greater clarity and brightness and improved rheological properties. Functionally, citric acid supported foam stability, and acetic and lactic acids improved emulsifying stability, notably in bovine gelatin. Additionally, the source of bone significantly affected overall quality, following the order pig ≥ beef > chicken. Acetic acid optimized the overall quality of the gelatin, and citric acid increased the yield, making pig gelatin the most promising for food applications.