Alkalinization as a non-thermal pretreatment to improve the physicochemical, functional properties, and Salmonella injury of liquid egg whites.

Abstract

Thermal pasteurization of liquid egg whites (LEW) ensures microbial safety but often compromises functional properties due to protein denaturation. This study investigated alkalinization as a non-thermal pretreatment to enhance the physicochemical and functional properties of LEW while inducing sub-lethal injury in Salmonella Enteritidis. The pH of LEW was adjusted using various concentrations of NaOH (0.1-1.1 M); 0.7 M NaOH was identified as the optimal concentration to achieve a target pH of 11.0, balancing minimal dilution with reduced protein aggregation. Physicochemical analysis revealed that alkalinization significantly increased LEW transparency (transmittance increased from 51.92 ± 0.60% to 86.42 ± 1.62%) and zeta-potential magnitude, attributed to electrostatic repulsion and protein unfolding. Functionally, pH-adjusted LEW (pH 10.1 and 11.0) exhibited superior protein solubility (>90%), foaming capacity, and emulsifying activity index compared to the Control. The gel texture transformed from brittle to elastic, characterized by decreased hardness and increased resilience. Microbial studies demonstrated that storage at pH 11.0 for 6 h significantly reduced Salmonella populations (D-value decreased from 89.93 h to 3.90 h). Critically, a significant discrepancy between counts on non-selective (TAL) and selective (XLD) media indicated a high rate of sub-lethal injury (∼30%), highlighting the efficacy of alkaline stress in compromising pathogen membrane integrity. These findings suggested that controlled alkalinization is a promising strategy to improve both the safety and industrial functionality of liquid egg products.