Investigation of gelation properties and efficiencies of proteins obtained from animal-based wastes

Gelatin is a natural protein with many uses, produced from animal sources such as fish, pork, bovine and chicken. It is obtained by the controlled hydrolysis of collagen from these sources. Gelatin is a pure protein with various functional and technological properties such as gelling, thickening, film forming and emulsifying. Skin and bones after slaughter in slaughterhouses and mechanically deboned meat (MDM) residues sent to rendering are rich sources of collagen. The aim of this thesis study was to obtain collagen and gelatin from bovine skin and bone, sheep skin and bone, chicken skin, chicken shanks and MDM residues by pretreatment (acid treatment), demineralization and thermal extraction processes and to compare their physicochemical, functional and textural properties. In the study, protein content and conformation, water and oil binding capacity, emulsion properties, color and transparency, gel strength and TPA parameters of collagen/gelatin fractions extracted from different animal sources were evaluated. According to the findings, the amount of gelatin in the skin and bone samples indicated remarkable differences. According to the findings, chicken shanks had the highest (~31 mg/ml) protein content, while bovine bone had the lowest (~25 mg/ml) protein content among bone/MDM samples. In skin samples, chicken skin had the highest (~60 mg/ml) protein content, while the lowest (~30 mg/ml) protein content was found in bovine skin. In addition, the highest collagen and gelatin yields were obtained in chicken shanks sample with 3,54% and 3,97%, respectively. Among the skin samples, the highest collagen and gelatin yields were obtained in chicken skin samples with 5,92% and 8,60%, respectively. Although the protein profiles of bone and skin samples included γ, β, α ve sub-α chain protein units, differences in protein conformation were observed. The highest transparency was observed in bovine skin (~100%), while gelatin fractions with the highest water and fat binding capacities were obtained in the shanks sample (~185%), sheep skin sample (~384%), respectively. When the gelatins obtained were evaluated in terms of gel strenght, chicken skin (~109 g) was low, sheep bone (~204 g) and chicken shanks (~182 g) medium, chicken MKS mixture (~336 g), sheep skin (~230 g) and bovine skin (~476 g) were found to have high gel strength. The presented study revealed that it is possible to obtain protein with different properties and which can be used in industry from animal waste.