Modification of Perilla (Perilla frutescens (L.) Britt.) Seed Protein via Physical Treatments for Enhanced Gelation Properties

Abstract

Perilla (Perilla frutescens (L.) Britt.) seed protein, an underutilized resource derived from medicinal and edible plants, was subjected to ultrasound (400 W, 20 min), pH-shifting (pH 12.0, 1 h), and high-pressure homogenization (90 MPa, 3 cycles), applied individually or in combination, and subsequently fermented with probiotics to induce gel formation. The triple combination (pH-shifting + high-pressure homogenization + ultrasound) produced the highest solubility increase (129%), smallest particle size, greatest random coil content, and maximal surface hydrophobicity and free sulfhydryl level. The triple-modified protein gels exhibited a highly homogeneous microstructure. Meanwhile, these gels achieved significant improvements (p < 0.05) in multiple functional and rheological properties, including gel strength, water-holding capacity, viscosity, and storage modulus, as well as the viable count. These results demonstrate that combined application of three physical modifications effectively restructures perilla seed protein and markedly improves its gelation behavior under fermentation, supporting its potential as a novel ingredient for fermented plant-protein gels or yogurt-like products.