Encapsulation of Citral by Sodium Carboxymethyl Starch and Sodium Caseinate: Antibacterial Activity Characterization and Evaluation

Citral exhibits favorable broad-spectrum antibacterial activity; however, it is prone to oxidative degradation or structural changes. To improve its stability and practical applicability, citral-loaded microcapsules were prepared using sodium carboxymethyl starch (CMS) and sodium caseinate (CS) via emulsification and freeze-drying. We then investigated the effects of the CMS-to-CS mass ratio on the physicochemical properties and microstructure of the microcapsules, and systematically evaluated the antibacterial activity and underlying mechanisms of the citral-loaded microcapsules against typical foodborne pathogenic bacteria and food-related bacteria. The results showed that when the CMS-to-CS mass ratio was 3:1, the microcapsules prepared exhibited the highest encapsulation efficiency (83.87%). The molecular interactions between citral and the wall materials were confirmed. The citral-loaded microcapsules demonstrated good thermal stability and a compact morphology with dense blocks. Furthermore, treatment with the citral-loaded microcapsules led to the leakage of intracellular contents and compromised the cell membrane integrity of Staphylococcus aureus, thereby inhibiting its normal physiological functions, as well as effectively disrupting bacterial aggregation at high concentrations. These findings offer a valuable reference for future studies aimed at improving the stability of citral when used as an antibacterial agent and at enhancing its practical application value.