Rheological Characterization Bovine Serum Albumin Gels Induced by High Hydrostatic Pressure

Abstract

Similarly to heating, non-thermal technologies like High Hydrostatic Pressure (HHP) are able to affect the native conformation of proteins, causing denaturation, aggregation or gelation. The aim of this work is to evaluate the effect of product’s chemical-physical characteristics, namely pH and protein concentration, and process parameters, namely pressure level and processing time, on the stability of the structure of a particular allergen, the Bovine Serum Albumin (BSA) as well as to individuate the most appropriate processing conditions to induce protein denaturation and/or aggregation. Different amounts of BSA protein were dissolved in phosphate buffer (50 mM) at three different pH (6, 7 and 8), to obtain concentration levels of 12, 25, 50 and 100 mg/mL. The HHP process was carried out at pressure levels in the range between 700 and 900 MPa and treatment time of 15 - 25 min. The structural characteristics of HHP-treated BSA suspensions were assessed by means of a complete rheological screening (strain sweep, frequency sweep and temperature ramp tests) in dynamic regime. Experimental data demonstrate that the rheological parameters, namely the loss and the storage moduli, increase as pressure levels and processing time increase, especially at higher concentrations, whereas a constant critical strain of about 0.3% is detected. The pH and protein concentration mainly control the denaturation influencing the threshold value of the processing conditions at which the gelation occurs. At processing conditions below the threshold values, however, the structure of BSA can be reversibly damaged.