This work describes the effect of isostatic pressure 500 MPa on tryptic and chymotryptic hydrolysis of α- and β-casein, bovine serum albumin (BSA), β-lactoglobulin (β-Lg) and α -lactalbumin (α-La). Digestion was also conducted at atmospheric pressure. The extent of hydrolysis and peptide profiles were analysed by gel-permeation and reverse-phase high-performance liquid chromatographies. The residual immunochemical reactivities of the protein hydrolysates were assessed by the Streptavidin ImmunoCAP system (Phadia) for determination of specific immunoglobulin type E (IgE) antibodies. We have found very significant changes of the peptide profiles and a progressive reduction in residual-intact proteins after applying high pressure during tryptic proteolysis of β-Lg and BSA and chymotryptic proteolysis of β-Lg, α-La and BSA. A statistically significant decrease of the residual immunochemical reactivities of β-Lg tryptic and α-La chymotryptic hydrolysates prepared under high pressure, in comparison with the control samples hydrolysed at atmospheric pressure, was also observed.

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The effects of the polyvinyl alcohol (PVA) concentration on mechanical properties of hydrogels based on blends of native or denatured collagen / PVA were examined. Blends of PVA with collagen were obtained by mixing the solutions in different ratios, using glycerol as a plasticizer. The solutions were cast on polystyrene plates and the solvent was allowed to evaporate at room temperature. Uniaxial tensile tests were performed in order to obtain the initial modulus of elasticity (up to deformation 0.1), the ultimate tensile stress and the deformation at failure of the material in the water-saturated hydrogel form. It was found that the material was elastic and the addition of PVA helped to enhance both the ultimate tensile stress and modulus of elasticity of the films. Samples prepared from denaturated collagen showed the higher ultimate tensile stress and the deformation at failure in comparison with those prepared from native collagen. The results suggest that we could expect successful application of the collagen/PVA biomaterial for tissue engineering.

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