Structural changes to the three sensitive food proteins, ovalbumin, β-lactoglobulin and lysozyme were examined following a series of high pressure processing experiments. The proteins prepared at specific pH were pressurized up to 600 MPa and held for periods of up to 30 min. Changes to the secondary and tertiary by examination of circular dichroism spectra revealed that the structure of the three proteins behaved differently to both the applied pressure and holding time. The notable effects were found to occur to both ovalbumin and β-lactoglobulin while lysozyme was found to be the most pressure resistant. For each of the proteins, it also appears that the processing conditions applied at specific pH act in combination to bring about structural change.