Structural modifications induced by high pressure homogenization under acidic and alkaline conditions improve the functionality of pequi almond (Caryocar brasiliense Camb.) proteins

Pequi almond ( Caryocar brasiliense Camb.) is a protein-rich agro-industrial by-product. However, the application of pequi almond protein (PAP) is limited by its low solubility. High pressure homogenization (HPH) combined with pH modulation is a promising strategy to overcome this limitation. In this study, PAP was processed by HPH at acidic (pH 2.0) and alkaline (pH 10.0) conditions using pressures of 60-120 MPa for one cycle. Structural analyses, including particle size, zeta potential, polydispersity index, FTIR and Raman spectroscopy, intrinsic fluorescence, and free sulfhydryl groups, were performed at the respective processing pH. In macrostructural terms, HPH reduced particle size (<81%) and improved protein dispersion, as evidenced by a decrease in the polydispersity index (<54%). At the molecular level, HPH induced pH-dependent structural rearrangements, with an increase in random structures at pH 2.0, indicating partial denaturation, and a predominance of more ordered structures (α-helix and β-turns) at pH 10.0, suggesting controlled molecular association and structural reorganization. Intrinsic fluorescence and sulfhydryl group analyses confirmed HPH-induced conformational changes, reflected by increased exposure of aromatic residues and free-SH groups. Solubility and colloidal stability were subsequently evaluated at pH 6.0. Under these conditions, HPH pretreatment enhanced PAP solubility, reaching 63.5% after alkaline processing at 100 MPa, and improved colloidal stability, as demonstrated by a reduction of up to 85.4% in the Turbiscan Stability Index (TSI). Overall, these results demonstrate that HPH is an effective strategy to tailor PAP structure and enhance its functional performance, supporting its potential application in plant-based beverages, emulsion-based products, and nutritional supplements. • HPH processing under acidic and alkaline conditions modulated PAP structure • Multi-spectroscopic analyses revealed protein unfolding after HPH treatment • HPH, mainly under alkaline conditions, increased PAP solubility measured at pH 6.0 • Particle size reduction induced by HPH improved protein dispersion and colloidal stability