This study investigated the valorization of chicken feet, an underutilized poultry by-product, through enzymatic hydrolysis to obtain a protein hydrolysate with improved functional properties. Enzymatic treatment was carried out using Enzy-Mix U100 and collagenase from Streptomyces lavendulae, with cheese whey applied as a process medium. The resulting protein hydrolysate contained 59.1% protein and was characterized by high levels of glycine (31.64 g/100 g protein), hydroxyproline (10.91 g/100 g protein), and alanine (10.58 g/100 g protein). The hydrolysate exhibited strong techno-functional performance, with a water-binding capacity of 580%, an emulsifying activity index of 166 m²/g, and an emulsion stability index of 31 min. Microstructural analysis revealed irregular porous particles typical of freeze-dried protein hydrolysates, reflecting structural modification of collagen during enzymatic treatment. Mineral analysis showed notable levels of sodium (463.1 mg/100 g) and magnesium (351.8 mg/100 g). Microbiological evaluation demonstrated high sanitary quality, with a total viable count of 100 CFU/g and absence of coliforms, Escherichia coli, yeasts, and molds in 1 g of product. The technological process reduced the characteristic odor of chicken feet while maintaining a light color and good dispersibility. These findings confirm the potential of enzymatic hydrolysis as a sustainable strategy for converting poultry by-products into safe, value-added functional protein ingredients for food applications.

The protein fraction of slaughterhouse blood remains underutilized primarily due to challenges associated with its instability during processing and storage. This study aimed to develop stable bovine blood plasma gels using selected lactic acid bacteria and flaxseed oil cake flour. Various lactic acid bacteria strains were incorporated at concentrations of 5–20% (w/w), and gel properties such as pH, gelation time, yield stress, and freeze–thaw syneresis were evaluated. Optimal gelation was achieved at 20% inoculum, producing fibrin networks with yield stresses (372 Pa) comparable to recalcified controls (410 Pa), but accompanied by high serum loss and undesired acidic aromas at higher bacterial densities. Incorporating 5% hydrated flaxseed oil cake flour successfully reduced syneresis below 10%, improved water-holding capacity (135%), and prevented development of off-flavors, demonstrating beneficial interactions between flaxseed polysaccharides and blood plasma proteins. Thus, combining a 20% mixed lactic starter with 5% flaxseed cake flour yielded a stable plasma gel suitable for meat product applications, balancing rapid gel formation, high moisture retention, desirable rheological properties, and neutral sensory characteristics.

This study investigated the technological feasibility of using a pre-structured bovine blood plasma–flaxseed composition as a functional partial substitute for beef in emulsion-type sausages. Five formulations containing 0–30% replacement were evaluated to determine effects on structural, nutritional, and microbiological properties. Incorporation of the structured composition modified the functional balance of the protein system: water-holding capacity remained stable (p > 0.05), while fat-holding and emulsifying capacities improved at higher inclusion levels (p < 0.05), indicating enhanced interfacial stabilization of the fat phase. Progressive softening of texture was observed, with significant reductions in hardness and chewiness at 30% replacement (p < 0.05). Cooking loss increased at elevated substitution levels but remained within acceptable technological limits. During refrigerated storage, microbial counts remained below safety thresholds. A 15–25% replacement level provided the most balanced performance, maintaining sensory acceptability while improving lipid stabilization. The results demonstrate that structured plasma-based systems can function as effective protein–emulsion modifiers in meat formulations, supporting sustainable valorization of slaughter by-products.

Chicken skin and related poultry by-products are rich in collagen and lipids but remain underutilized, creating opportunities for their conversion into value-added functional ingredients. This study developed chicken-skin-based protein–fat emulsions and evaluated the effect of changing the fat-to-hydrolysate ratio on their physicochemical, techno-functional, compositional, rheological, oxidative, and microbiological properties. Four formulations containing 13.5–15.0% chicken fat and 6.8–5.3% chicken skin protein hydrolysate were prepared, while chicken skin and water were maintained at 36.4 and 43.3%, respectively. Three independent production batches were prepared for each formulation. The emulsions showed similar pH (4.82–4.99) and water activity (0.979–0.996) (p > 0.05). Water-holding capacity decreased from 78.74% to 73.60%, whereas fat-holding capacity increased from 41.00% to 62.40% (p < 0.05). Variant 3 showed the highest emulsion stability (22%) and an emulsifying capacity of 56%, while Variant 4 had the highest apparent viscosity (577 mPa·s) but the lowest yield stress (2.011 Pa). The emulsions exhibited a collagen-rich amino acid profile, and oleic, palmitic, and linoleic acids predominated in the lipid fraction. During refrigerated storage, TBARS increased from 0.34–0.37 to 2.19–2.51 mg MDA/kg, while total viable counts reached 3.83–4.03 log CFU/g by day 14. Among the tested formulations, Variant 3 showed a favorable combination of stability and emulsifying and rheological properties. These results identify chicken-skin-based protein–fat emulsions as candidate functional ingredients for further evaluation in food formulations.