The effect of high-pressure homogenization on physicochemical properties, flow behavior and thermal gelation of commercial pea protein isolate

As an emerging protein source in plant-based foods, commercial pea protein isolate (cPPI) often suffers from poor thermal gelation properties due to protein denaturation and aggregation stemming from its production process. High-pressure homogenization (HPH) is a promising physical method to disrupt protein aggregates. This study examined the effect of HPH on the physicochemical properties (i.e., protein dispersibility, particle size, surface hydrophobicity, and free SH groups), flow behavior and thermal gelation (rheological gel properties as well as molecular mechanisms involved) of an 8.5% w/w cPPI dispersion homogenized at 50, 100, and 200 MPa, compared to an unhomogenized cPPI dispersion. HPH significantly increased protein dispersibility (from 24% to 86%) and reduced particle size ($D_{[3,2]}$ from 44.0 to $0.5\mu m$). Surface hydrophobicity increased, while the content of free SH groups declined. Upon HPH treatment, the flow behavior shifted from Newtonian to Bingham pseudoplastic, with this shift intensifying at 200 MPa. Thermal gelation of HPH treated cPPI dispersions exhibited a more elastic (lower $tan\delta$), more stable (lower $n^{\prime }$), stiffer (higher $K^{\prime }$), and more deformable (higher ${ϵ}_c$) and less brittle (higher ${ϵ}_y$) gel network, particularly at 200 MPa. The thermal gelation was primarily driven by hydrophobic interactions. Disulfide bonds and hydrogen bonds played limited roles. These findings indicated that HPH disrupts large indispersible denatured protein aggregates into smaller dispersible ones, exposing hydrophobic regions that are critical for thermal gelation of cPPI dispersions.