The effect of chemical modifications on rheological properties of collagen from of baltic cod (Gadus morhua) skin stabilized by interaction with κ-carrageenan

The κ-carrageenan-collagen complex was precipitated by κ-carrageenan from solution of collagen sourced from Baltic cod (Gadus morhua) skin in 0.5M acetic acid. The influence of glutaraldehyde or EDC [1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride] concentration on rheological properties of κ-carrageen-collagen complex was examined. At 5 to 30mM glutaraldehyde content in 0.5 κ-carrageenan-collagen dispersion a rapid increase in its viscosity was observed, which remained unchanged over 120 min. Further increase in glutaraldehyde concentration to 30mM caused enhanced viscosity and shorten time of complex stability, which not exceed 45 min. The level of dispersion viscosity caused by glutaraldehyde cross-linking ranged from 70 to 420 mPa.s. For comparison, at EDC concentrations from 30 up to 180mM the viscosity of suspension changed after 200 min from 130-280 mPa.s. Glutaraldehyde not influenced on mechanical resistance of the membranes as well as elongation at the break. However, EDC cross-linking significantly increased the flexibility of the membranes and decreased the stress needed at break. It was observed that at 30 mM concentration of EDC the tensile strength of the membranes was reduced from about 21 MPa to 11 MPa, and the elongation at the break was enhanced from about 0.4 to 20%. At 60mM concentration of EDC the stress at break was reduced to 1.4 MPa, whereas the elongation at break was about 17%. Cross-linking of the membranes decreases their hydrophilic properties.