Industrial symbiosis: characterization of hydrogels formed with collagen and glycosaminoglycan (GAG) derived from chicken by-products and their use in the development of functional fruity gels
Project no. 24142 · Status: Kapanmış (Yayın bekleniyor) · 2022
Summary
<p>In this thesis study, in line with the principle of sustainability, poultry processing by-products were valorized to obtain high value-added bioactive compounds, namely collagen and chondroitin sulfate. In the subsequent stage, an innovative hydrogel system was designed to explore the synergistic interaction of the obtained collagen and chondroitin sulfate with hyaluronic acid. In this context, the effects of varying polymer ratios and genipin concentrations—hence different crosslinking densities—on the morphology, mechanical properties, and stability of the resulting gel matrix were comprehensively analyzed. The hydrogel produced under optimized conditions was utilized in fruit-based gel formulations to develop a potential functional food product with an innovative approach. Among poultry by-products, the sternum, trachea, gizzard membrane, and thoracic vertebrae were evaluated as raw materials for the extraction of collagen and chondroitin sulfate. Following enzymatic hydrolysis using lactic acid and pepsin, the collagen contents of the extracts were determined as 71.23 ± 0.61% for sternum, 41.52 ± 3.07% for trachea, and 20.72 ± 0.87% for thoracic vertebrae. No collagen could be obtained from the gizzard membrane. SDS-PAGE and FTIR analyses revealed that the collagen extracted from the sternum was predominantly Type II, whereas that from the trachea was Type I. Both collagen samples exhibited maximum solubility at pH 6. A total of eighteen amino acids, including all essential ones except tryptophan, were identified in the collagen samples. Surface morphology analysis showed the characteristic porous and fibrous structure of collagen. Chondroitin sulfate (CS) was obtained via enzymatic hydrolysis using phosphate buffer and papain. The CS contents were determined as 74.94 ± 3.23% for the sternum and 63.55 ± 5.15% for the trachea, while no CS was obtained from the thoracic vertebrae or gizzard membrane. FTIR analysis revealed that chondroitin-4-sulfate was the dominant CS type in both extracts. Aggregated structures, formed due to the presence of core proteins associated with chondroitin sulfate, were prominently observed in the extracts.For hydrogel production, collagen and chondroitin sulfate extracted from chicken sternum, along with commercial hyaluronic acid (HA), were used. The hydrogels were prepared using a collagen solution at pH 7.4 and a CS/HA mixture at pH 3. The effects of three different polymer ratios (1:3, 1:5, and 1:8) and genipin concentrations (0.25 mM, 0.5 mM, and 0.75 mM) on the structural and rheological properties of the hydrogels were investigated. Compared to the control samples (0 mM GP), more than a fourfold increase in G' values was observed in genipin crosslinked hydrogels. All hydrogels exhibited more pronounced shear-thinning and strain-stiffening behavior in the LAOS region. As the collagen ratio and genipin concentration increased, the elasticity and resistance to deformation of the hydrogels also improved. Fruit gels prepared with a 1:8 polymer ratio and 0.75 mM GP concentration were found to be free from cytotoxic effects and microbiologically safe. Additionally, the gels were observed to significantly preserve their structural integrity during the digestion process and to exhibit promising textural properties for food applications.</p>