Effects of high hydrostatic pressure on the conformational structure and the functional properties of bovine serum albumin

Abstract

Abstract Non-thermal technologies, such as High Hydrostatic Pressure (HHP), are able to induce extensive changes in the structure of biological macromolecules, namely proteins. HHP treatments disrupt the electrostatic interactions, which stabilize the quaternary and the tertiary structure of the proteins, and activate the reactions of sulfhydryl-disulfide bond exchange. These structural changes result in the dissociation and refolding of proteins during HHP treatments, and consequently in the modification of protein functional properties, namely physicochemical properties (solubility, binding and surfactant properties, water and oil absorption capacity, emulsifying and foaming properties). The technological behavior of the proteins in food preparation, processing, storage, as well as their contribution to determine quality perception of foods mainly depends on these functional properties. This work aims at investigating the effects of HHP treatments on the conformational (quaternary, tertiary and secondary) structure and the functional properties of a globular water soluble protein, the Bovine Serum Albumin (BSA). BSA (50–100 mg/mL) solutions in Sodium Phosphate Buffer were processed at different pressure levels (100–500 MPa) and treatment times (15, 25 min). BSA unfolding and refolding were analyzed in terms of free sulfhydryl (SH) groups, changes of secondary structure, foaming and emulsifying properties. Analyzing the experimental data it can be concluded that the unfolding of BSA samples with a concentration of 50 mg/mL occurred in the pressure range between 100 and 400 MPa. In fact an increased number of the free SH groups as well as an improved foaming and emulsifying ability were detected in the treated samples. Pressure levels above 400 MPa promoted the interactions between adjacent polypeptide chains and the formation of soluble high molecular mass aggregates. The concentration of the protein in the samples, also, controlled the occurrence of unfolding and aggregation. Extensive changes in BSA secondary structure were observed at pressure level above 300 MPa, for longer processing times and higher protein concentrations. In these processing conditions β-sheet aggregates were likely to replace the initial α-helixes. Industrial relevance The paper consists in the study of the Effects of High Hydrostatic Pressure processing (HHP) on the conformational structure and the functional properties of Bovine Serum Albumin. he work proposes an innovative technology for Food Industries that can be widely used for food conservation and to induce protein modifications in the same time. For this reason the technology represents a good tool for the production of hypoallergenic compounds especially in the field of dairy products and infant formula companies.