Enhancing probiotic viability and vitamin D₃ stability in co-microcapsules: Collaborative effects of W₁/O/W₂ double emulsion and HPMCP-fortified composite coating.

Traditional spray-dried microencapsulation systems often exhibit limited thermal protection during drying process, inadequate barrier functionality throughout storage, and suboptimal control over gastrointestinal release. To address these limitations, the present study developed a spray-dried microencapsulation platform using a W₁/O/W₂ double emulsion combined with a hypromellose phthalate (HPMCP)-enhanced composite coating to co-deliver the probiotic Lactiplantibacillus plantarum JYLP-326 and vitamin D₃ (vitD₃). First, the physicochemical properties of the composite coating materials and the resulting microcapsules were systematically characterized using various experimental and simulation methods. Subsequently, the influences of W₁/O/W₂ architecture and HPMCP incorporation on microcapsule performance were comprehensively investigated. The W₁/O/W₂ structure was found to be crucial in protecting probiotics during spray drying, attributable to the energy-absorbing and thermal-insulating properties of the intermediate lipid phase. In contrast, HPMCP integration was more effective in enhancing storage stability and facilitating pH-responsive release during simulated digestion, mechanistically attributed to a reinforced barrier network, higher glass transition temperature, and increased hydrophobicity. Compared to formulations lacking either W₁/O/W₂ structure or HPMCP, the combined W₁/O/W₂-HS microcapsules showed the highest probiotic viability after drying (93.6 ± 1.7%), lowest probiotic inactivation (0.39 ± 0.04 log CFU g^-1), and greatest vitD₃ bioaccessibility (71.5 ± 1.2%) post-digestion. They also demonstrated the lowest inactivation rates during storage (-0.060 log CFU g^-1 day^-1 for probiotics and -0.305% day^-1 for vitD₃). This study highlights how rational emulsion architecture and wall material design can address processing and storage challenges, offering an industrially scalable and effective strategy for co-encapsulating nutrients with diverse chemical properties.

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