Insight into the formation of layer-by-layer emulsions stabilized by sodium caseinate and montmorillonite studied with ITC for carvacrol retention and spray drying efficiency

Abstract

This study investigates the formation of layer-by-layer emulsions for carvacrol encapsulation, using sodium caseinate as the first layer, and montmorillonite particles as the second layer, under two pH conditions (3 and 7). Dynamic light scattering and zeta potential results indicated improved stability at montmorillonite to caseinate emulsion ratios of 2:1 at pH 7 and 4:1 at pH 3, characterized by stable zeta potentials of −33.3 ± 1.87 mV and − 23.7 ± 1.97 mV, respectively. Isothermal titration calorimetry analysis confirmed that electrostatic interactions were the primary driving force for multilayer formation at pH 3, while hydrophobic and hydrogen bonding interactions likely dominated at pH 7. The process was spontaneous at both pH levels, with negative Gibbs free energy. Layer-by-layer emulsions showed superior encapsulation efficiency and retention of carvacrol, with a loading capacity of 21.84 ± 0.09 mg/g at pH 7. Furthermore, these formulations enhanced the antimicrobial efficacy of carvacrol. • Double-layer emulsions were prepared using layer-by-layer deposition technique. • Montmorillonite was successfully used as the second emulsion layer. • Carvacrol is better retained in double-layer than single-layer emulsions. • Spray-dried microcapsules with two layers show stronger antimicrobial properties.