Ultrasound and enzymolysis pretreatment induce pea protein to form new fibrils for efficient delivery of astaxanthin

Abstract

Unlike natural proteins, protein fibrils exhibit superior chemical stability, reactive functional groups, and delivery properties. However, the application process faces great challenges, such as slow fibrillation processes and low conversion efficiency. The effects of ultrasound and enzymolysis pretreatment on the conformation and physicochemical properties of pea protein fibrils (PPFs) during the lag, growth, and plateau phases were investigated, and a novel astaxanthin (AST) delivery system was developed. The results indicated that both ultrasound and enzymolysis pretreatment alters the fibrillation process by disrupting and reorganizing hydrophobic interactions, dityrosine covalent bonds, and disulfide bonds between molecules. Notably, ultrasound increased the flexibility, surface hydrophobicity, and dispersibility of pea proteins, resulting in forming PPFs with a smaller scale (130.57 nm–185.27 nm). Enzymolysis pretreatment significantly shortened the hydrolysis time of pea protein and increased the β-sheet proportion (41.4 %) of PPFs, thereby promoting the formation of more and larger scale PPFs (412.27 nm–838.47 nm) through molecular folding and aggregation of more fibril building blocks. Among these, albumins (<17 kDa) were the primary subunits of PPFs at the plateau phase. Furthermore, the encapsulation of AST by PPFs resulted in the formation of amorphous complexes, which enhanced the functional properties of AST. In particular, the PPF/AST complex under ultrasonic co-enzymolysis pretreatment exhibited the highest DPPH radical scavenging activity (56.35 %), ABTS radical scavenging activity (62.22 %), AST retention (50.15 %), and bio-accessibility (37.64 %). This study offers significant insights into the functional regulation of PPFs and the utilization of encapsulated bioactives.