Long-time high-pressure processing of a patatin-rich potato proteins isolate: impact on aggregation and surface properties

In this study, a 4% (w/w) dispersion of a commercial patatin-rich potato protein isolate (Po-PI) was pressurised at 400 MPa up to 48 h at 20 degrees C. Protein aggregation induced by high-pressure processing (HHP) was followed by dynamic light scattering, intrinsic fluorescence (in-situ or ex-situ) or SAXS analysis. Surface properties (surface hydrophobicity and interfacial properties) of the HHP-induced aggregates were also investigated. A gradual dimer dissociation/protein unfolding was observed under pressure. Po-PI exhibited a slow relaxation time under pressure. Long-time HHP (>4 h) induced significant modification of the Po-PI protein structure with partial non-reversible unfolding. After 48 h of pressurisation at 400 MPa, large aggregates (160 nm) were obtained and a monomodal distribution in intensity and in number frequency was observed indicating a controlled aggregation. Up to 24 h of pressurisation at 400 MPa, intermediate states were obtained after high-pressure release. SDS-PAGE profiles showed that HHP-induced aggregation of Po-PI was driven by non-covalent interactions. All high-pressure processed dispersions displayed a higher surface hydrophobicity as compared to non-treated Po-PI. Po-PI dispersion treated for 8 h at 400 MPa presented the lowest adsorption rate, the highest final surface tension and formed the most rigid interfacial film. Po-PI showed resistance to moderate pressure levels (400 MPa) and long pressure application times were required to induce significant protein denaturation/aggregation (>= 24 h) and to optimally modify its interfacial properties (8 h).