Structural and Molecular Properties of Condensed Globular Proteins from High Pressure Perspectives

The marked increase in the application of high pressure processing in the food industry worldwide created a range of novel products with enhanced natural flavour and retention of natural vitamins compared to thermally treated products. The present treatise deals with the effect of high hydrostatic pressure on the structural properties of globular proteins with potential industrial interest in a wide range of high-solid foods. Globular proteins exhibit glassy behaviour at subzero temperatures in high-solid preparations (e.g. 80%, w/w) recorded rheologically and modelled theoretically. DSC and FTIR results revealed that disulphide bonds are involved in the pressure stability of globular proteins. BSA comprises 17 disulphide linkages being the most stable at high pressure, whereas whey protein with 2 disulphide bonds is the most affected globular protein under high pressure (600 MPa for 15 min at ambient temperature). However, ovalbumin with one disulphide linkage does not follow this sequence, an outcome that raises the issue of the effect of surface hydrophobicity of the molecule. Thus, ovalbumin has a hydrophobicity value (So) of around 100, which falls between that of BSA (So ∼ 2200) and whey protein (So ∼ 35), indicating that both phenomena, i.e. disulphide linkages and surface hydrophobicity, are combined in the observed structural properties of globular proteins following application of high pressure. This may have industrial significance in relation to the formulation and stabilisation of “functional food” products as well as in protein ingredients and concentrates by replacing spray dried powders with condensed HPP-treated pastes that maintain techno- and biofunctionality.