Increasing pressure and number of passes during dynamic high-pressure microfluidization treatment modulates the structural, techno-functional, and rheological properties of perilla seed protein

Physical modification methods, like dynamic high-pressure microfluidization (DHPM), offer a novel means to enhance the functionality of plant proteins for food applications. This study systematically explored the impact of both pressure (100, 150, and 200 MPa) and passes (3 and 6 passes) on the structural, techno-functional, and rheological properties of perilla protein isolate (PPI) as a representative model protein. Scanning electron microscope (SEM) images revealed that the high shearing forces during DHPM treatment altered the protein microstructure, transforming thick protein blocks into smaller, thinner flakes. DHPM effectively dissociated large insoluble aggregates (> 1 μm) into soluble ones, with re-aggregation observed at higher passes (6 passes). Consequently, DHPM significantly increased PPI solubility from 48.45 % to 83.23 %. DHPM (on case-to-case basis) induced alterations in the secondary structure and partially unfolded the protein structure, led to changes in surface hydrophobicity, sulfhydryl content, fluorescent intensity, and UV absorbance. Therefore, it enhanced oil holding capacity, foaming and emulsification properties, antioxidant activities, and thermal stability. Additionally, DHPM treatment reduced the apparent viscosity and showed shear-thinning behavior of protein dispersions. Notably, DHPM at 100 MPa-3 passes and 200 MPa-3 & 6 passes transformed protein dispersions from a weak gel-like, i.e., storage modulus (G') > loss modulus (G") to a liquid-like (G" > G') character. These findings underscore the potential of utilizing both pressure and passes to tailor the functionality of plant proteins for various food applications.