Effects of Hot-Pressure Extraction Time on Composition and Gelatin Properties of Chicken Bone Extracts

Hot-pressure extraction was utilized in this study to extract proteins from chicken bones at 130 °C. The obtained extracts were further used to prepare gelatin gels. Results demonstrated that the extraction time can significantly affect the composition of the chicken bone extracts (P < 0.05). High-performance liquid chromatography (HPLC) analysis indicated that the protein fraction of molecular weight (MW) >30 KDa was only visible in the extracts collected between 40 and 60 min. The highest contents of hydroxyproline, imino acids, and hydrophobic amino acids were all achieved in the chicken bone extracts after 120 min of extraction, being 3.9, 7.7, and 16.0 mg/g, respectively. The prepared gelatin properties were evaluated in terms of viscosity, storage and loss modulus, stability, gel strength, and their microstructures. Results indicated that gelatins made from chicken bone extracts of 20, 40, and 60 min extraction had better properties compared to that of 90 and 120 min. Significant correlations were identified between gelatin's composition and properties (P < 0.05). The abundance of proteins with MW of <10 KDa and 10 to 30 KDa was found to be the predominant factor that can affect the gelatin's properties. This study illustrated a promising and natural way to obtain edible gelatins from chicken bones.