Molecular-level regulation of black soldier fly albumin through ultrasound-assisted pH-shifting and succinylation: Effective suppression of lysinoalanine formation and improved emulsifying properties

Abstract

Lysinoalanine (LAL) formation during alkaline processing compromises protein safety. This study developed a molecular-level strategy to regulate black soldier fly larvae albumin (BSFLA) by integrating ultrasound-assisted acidic/alkaline pH-shifting (pH 1.5/12 -US) with succinylation (SA). Succinylation selectively targeted the ε-amino groups of lysine residues, increasing surface negative charge, hydrophilicity, and molecular weight, and effectively eliminating LAL when the N-succinylation degree exceeded 70%. The pH 1.5/12 -US pretreatment promoted conformational unfolding and increased lysine accessibility, thereby enhancing succinylation efficiency and enabling molecular-level suppression of LAL formation. Beyond safety improvement, the pH 1.5 -US-SA treatment enhanced electrostatic repulsion, particle dispersion, and viscosity, leading to markedly improved emulsifying performance. Although equilibrium interfacial pressure decreased after modification, emulsification was governed by a structural flexibility coordinated rather than an adsorption density driven mechanism. This work provides a molecular framework for simultaneous safety regulation and functional enhancement of insect proteins, supporting their safe and sustainable utilization in food systems. • Designed a site-directed Lys succinylation approach for molecular-level inhibition of LAL. • LAL was eliminated when DA ≥70%, ensuring molecular safety. • pH 1.5/12 -US pretreatment boosted site-directed succinylation of BSFLA. • Proposed a flexibility coordinated emulsification mechanism replacing adsorption driven model. • pH 1.5 -US-SA achieved optimal synergy, enhancing EAI and ESI by 412% and 1514%.