Interactions, transformation, and functionality: Lactic acid bacteria fermentation of egg liquid as a novel food...

Eggs are predominantly consumed as basic food ingredients, with limited application in value-added products. Lactic acid bacteria fermentation offers a promising strategy to transform egg matrices into functional food ingredients. This review provides a comprehensive and critical overview of how LAB drives substrate consumption-including proteins, lipids, and carbohydrates-generates bioactive metabolites such as organic acids, flavor compounds, and free amino acids, and induces structural rearrangements in egg proteins at both macroscopic and molecular levels. These changes collectively improve functional properties including solubility, texture, rheology, emulsifying capacity, and foaming stability via mechanisms involving proteolysis, pH-driven aggregation, and redox balance. Importantly, fermentation outcomes are highly condition-dependent-the direction and extent of changes depend on substrate composition, protein concentration, pH, and strain selection. By integrating substrate transformations, structural modifications, and functional outcomes into a unified framework, this review provides mechanistic insights for developing LAB-fermented egg products with enhanced quality and health-promoting potential.