Macroscopic and structural consequences of high-pressure treatment of ovalbumin solutions

The effects of high pressure on the solubility and on some structural features of ovalbumin were investigated on protein solutions at neutral pH, containing different protein concentrations and treated at 400-800 MPa for different times. Ovalbumin solutions were prepared in the presence and in the absence of common food ingredients, such as sucrose and NaCl, that could act as "protectants" against treatment-induced modification. Protein insolubilization occurred in the absence of protectants as a function of the protein concentration and the treatment intensity; it appeared to be a consequence of structural modifications involving in particular the tertiary structure of the protein, and it was completely prevented by blocking the free -SH groups in the protein. Several of the structural features of the protein were modified also when it was treated in the presence of protectants. Modifications depended on the treatment pressure and time and on the protectant used. All of the treated proteins showed an increased susceptibility to proteolysis by trypsin and a decrease in the recognizability by specific antibodies. These effects were particularly evident when treatments were performed in the presence of sucrose, which was less effective than NaCl in preventing structural modifications upon treatment.