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.